Micro to Nano Technologies
Doccedil Dr Eylem Guumlven
Micro to Nano Technologies
Micro - Prefix meaning one millionth 11000000
Nano ndash Prefix meaning one billionth 11000000000
The Powers of 10
10+0 1 Meter
10-1 10 Centimeters
10-2 1 Centimeters
10-3 1 Millimeter
10-4 100 Microns
10-5 10 Microns
10-6 1 Micron
10-7 1000 Angstroms
10-8 100 Angstroms
10-9 1 Nanometer
10-10 1 Angstrom
10-11 10 Pico meters
10-12 1 Pico meter
10-13 100 Fermis
10-14 10 Fermis
10-15 1 Fermi
10-16 01 Fermis
10-17 001 Fermis
10-18 0001 Fermis
Perspective of Length Scale
Size of an atom (01 nm)
1 m
1 mm
1 m
1 nm
Humans
Car
Butterfly
Gnat
1 km
Boeing 747
Laptop
Wavelength of Visible Light
Micromachines
Width of DNA (2 nm)
Smallest feature in microelectronic chips
Proteins (5-50 nm)
Biological cellNucleus of a cell
Aircraft Carrier
Size of a Microprocessor
Nanostructures amp Quantum Devices
Top DownTop Down
Bottom UpBottom Up
Resolving power of the eye ~ 02 mm
Perspective of Size
Water molecules ndash 3 atoms
Protein molecules ndash thousands of atoms
DNA molecules ndash millions of atoms
Nanowires carbon nanotubes ndash millions of atoms
Carbon nanotube
water molecule
Protein molecule
Molecule of DNA
wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm
How Small is a nm
1 microm = one millionth of a meter
1 nm = one billionth of a meter
asymp 150000 thickness of a hair
asymp a string of 3 atoms
If we shrunk all distances by 110000000000 X
The sun and earth would be separated by 1 m
A football field would be 1 nm
Human hair thickness ~ 50 microm
110000000 km
110 m
More than just sizehellip
Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis
Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling
Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility
Interesting phenomena
STM of dangling bonds on a SiH surface
httppubwebacnsnwuedu~mhe663
Electron tunneling
b
More than just size hellip
Interesting phenomena
Fluorescence of quantum dots of various sizes
Phonon tunneling
Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures
Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering
Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important
Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Micro to Nano Technologies
Micro - Prefix meaning one millionth 11000000
Nano ndash Prefix meaning one billionth 11000000000
The Powers of 10
10+0 1 Meter
10-1 10 Centimeters
10-2 1 Centimeters
10-3 1 Millimeter
10-4 100 Microns
10-5 10 Microns
10-6 1 Micron
10-7 1000 Angstroms
10-8 100 Angstroms
10-9 1 Nanometer
10-10 1 Angstrom
10-11 10 Pico meters
10-12 1 Pico meter
10-13 100 Fermis
10-14 10 Fermis
10-15 1 Fermi
10-16 01 Fermis
10-17 001 Fermis
10-18 0001 Fermis
Perspective of Length Scale
Size of an atom (01 nm)
1 m
1 mm
1 m
1 nm
Humans
Car
Butterfly
Gnat
1 km
Boeing 747
Laptop
Wavelength of Visible Light
Micromachines
Width of DNA (2 nm)
Smallest feature in microelectronic chips
Proteins (5-50 nm)
Biological cellNucleus of a cell
Aircraft Carrier
Size of a Microprocessor
Nanostructures amp Quantum Devices
Top DownTop Down
Bottom UpBottom Up
Resolving power of the eye ~ 02 mm
Perspective of Size
Water molecules ndash 3 atoms
Protein molecules ndash thousands of atoms
DNA molecules ndash millions of atoms
Nanowires carbon nanotubes ndash millions of atoms
Carbon nanotube
water molecule
Protein molecule
Molecule of DNA
wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm
How Small is a nm
1 microm = one millionth of a meter
1 nm = one billionth of a meter
asymp 150000 thickness of a hair
asymp a string of 3 atoms
If we shrunk all distances by 110000000000 X
The sun and earth would be separated by 1 m
A football field would be 1 nm
Human hair thickness ~ 50 microm
110000000 km
110 m
More than just sizehellip
Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis
Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling
Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility
Interesting phenomena
STM of dangling bonds on a SiH surface
httppubwebacnsnwuedu~mhe663
Electron tunneling
b
More than just size hellip
Interesting phenomena
Fluorescence of quantum dots of various sizes
Phonon tunneling
Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures
Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering
Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important
Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
The Powers of 10
10+0 1 Meter
10-1 10 Centimeters
10-2 1 Centimeters
10-3 1 Millimeter
10-4 100 Microns
10-5 10 Microns
10-6 1 Micron
10-7 1000 Angstroms
10-8 100 Angstroms
10-9 1 Nanometer
10-10 1 Angstrom
10-11 10 Pico meters
10-12 1 Pico meter
10-13 100 Fermis
10-14 10 Fermis
10-15 1 Fermi
10-16 01 Fermis
10-17 001 Fermis
10-18 0001 Fermis
Perspective of Length Scale
Size of an atom (01 nm)
1 m
1 mm
1 m
1 nm
Humans
Car
Butterfly
Gnat
1 km
Boeing 747
Laptop
Wavelength of Visible Light
Micromachines
Width of DNA (2 nm)
Smallest feature in microelectronic chips
Proteins (5-50 nm)
Biological cellNucleus of a cell
Aircraft Carrier
Size of a Microprocessor
Nanostructures amp Quantum Devices
Top DownTop Down
Bottom UpBottom Up
Resolving power of the eye ~ 02 mm
Perspective of Size
Water molecules ndash 3 atoms
Protein molecules ndash thousands of atoms
DNA molecules ndash millions of atoms
Nanowires carbon nanotubes ndash millions of atoms
Carbon nanotube
water molecule
Protein molecule
Molecule of DNA
wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm
How Small is a nm
1 microm = one millionth of a meter
1 nm = one billionth of a meter
asymp 150000 thickness of a hair
asymp a string of 3 atoms
If we shrunk all distances by 110000000000 X
The sun and earth would be separated by 1 m
A football field would be 1 nm
Human hair thickness ~ 50 microm
110000000 km
110 m
More than just sizehellip
Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis
Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling
Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility
Interesting phenomena
STM of dangling bonds on a SiH surface
httppubwebacnsnwuedu~mhe663
Electron tunneling
b
More than just size hellip
Interesting phenomena
Fluorescence of quantum dots of various sizes
Phonon tunneling
Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures
Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering
Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important
Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Perspective of Length Scale
Size of an atom (01 nm)
1 m
1 mm
1 m
1 nm
Humans
Car
Butterfly
Gnat
1 km
Boeing 747
Laptop
Wavelength of Visible Light
Micromachines
Width of DNA (2 nm)
Smallest feature in microelectronic chips
Proteins (5-50 nm)
Biological cellNucleus of a cell
Aircraft Carrier
Size of a Microprocessor
Nanostructures amp Quantum Devices
Top DownTop Down
Bottom UpBottom Up
Resolving power of the eye ~ 02 mm
Perspective of Size
Water molecules ndash 3 atoms
Protein molecules ndash thousands of atoms
DNA molecules ndash millions of atoms
Nanowires carbon nanotubes ndash millions of atoms
Carbon nanotube
water molecule
Protein molecule
Molecule of DNA
wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm
How Small is a nm
1 microm = one millionth of a meter
1 nm = one billionth of a meter
asymp 150000 thickness of a hair
asymp a string of 3 atoms
If we shrunk all distances by 110000000000 X
The sun and earth would be separated by 1 m
A football field would be 1 nm
Human hair thickness ~ 50 microm
110000000 km
110 m
More than just sizehellip
Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis
Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling
Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility
Interesting phenomena
STM of dangling bonds on a SiH surface
httppubwebacnsnwuedu~mhe663
Electron tunneling
b
More than just size hellip
Interesting phenomena
Fluorescence of quantum dots of various sizes
Phonon tunneling
Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures
Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering
Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important
Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Perspective of Size
Water molecules ndash 3 atoms
Protein molecules ndash thousands of atoms
DNA molecules ndash millions of atoms
Nanowires carbon nanotubes ndash millions of atoms
Carbon nanotube
water molecule
Protein molecule
Molecule of DNA
wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm
How Small is a nm
1 microm = one millionth of a meter
1 nm = one billionth of a meter
asymp 150000 thickness of a hair
asymp a string of 3 atoms
If we shrunk all distances by 110000000000 X
The sun and earth would be separated by 1 m
A football field would be 1 nm
Human hair thickness ~ 50 microm
110000000 km
110 m
More than just sizehellip
Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis
Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling
Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility
Interesting phenomena
STM of dangling bonds on a SiH surface
httppubwebacnsnwuedu~mhe663
Electron tunneling
b
More than just size hellip
Interesting phenomena
Fluorescence of quantum dots of various sizes
Phonon tunneling
Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures
Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering
Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important
Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
How Small is a nm
1 microm = one millionth of a meter
1 nm = one billionth of a meter
asymp 150000 thickness of a hair
asymp a string of 3 atoms
If we shrunk all distances by 110000000000 X
The sun and earth would be separated by 1 m
A football field would be 1 nm
Human hair thickness ~ 50 microm
110000000 km
110 m
More than just sizehellip
Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis
Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling
Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility
Interesting phenomena
STM of dangling bonds on a SiH surface
httppubwebacnsnwuedu~mhe663
Electron tunneling
b
More than just size hellip
Interesting phenomena
Fluorescence of quantum dots of various sizes
Phonon tunneling
Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures
Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering
Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important
Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
More than just sizehellip
Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis
Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling
Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility
Interesting phenomena
STM of dangling bonds on a SiH surface
httppubwebacnsnwuedu~mhe663
Electron tunneling
b
More than just size hellip
Interesting phenomena
Fluorescence of quantum dots of various sizes
Phonon tunneling
Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures
Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering
Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important
Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
More than just size hellip
Interesting phenomena
Fluorescence of quantum dots of various sizes
Phonon tunneling
Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures
Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering
Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important
Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Micro- and NanoManufacturing ndash from TechnologyMaterials to Application
Micro- and NanoManufacturing
Electronics amp Dispays
Pharmaceutical
AutomotiveTextiles amp Clothes
Materials Process-Technology
Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik
Aerospace
Energy
industry
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Microfabrication
Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition
CVD PVD Photolithography
Optical exposure PR Etching
Aqueous plasma
Many of these techniques are useful directly or indirectly in nanofabrication
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Nanofabrication
Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)
ldquoTop-Downrdquo Fabrication of device structures via monolithic
processing on the nanoscale
ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of
atoms molecules or other basic units of matter
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Current Micro Technologies
Photonics - Optical Apertures and Flow Orifices
Electronics ndash Semiconductor chips anodic bonding
MEMS ndash Micro Electro Mechanical Systems
Communication ndash Fiber optics switching interconnects
Biotechnology - cell filtration drug discovery
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Current Nano Technologies
Molecular manufacturing ndash Precision down to the atomic level
Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies
Medicine ndash Devices that will flow through the circulatory system
Nanocomposites ndash Assisting in vast improvements in material compositions
Electronics ndash Advanced CMOS and silicon transistor integration with lithography
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf
Micro scaling to Nano
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
MicroNanoFabrication Techniques
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Generalized Microfabrication
Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Photolithography
Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities
Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)
Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist
Soft bake to drive off excess solvent and to promote adhesion
Exposure
Post exposure bake (optional) to suppress standing wave-effect
Develop
Clean Dry
Hard bake to harden the PR and improve adhesion to the substrate
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Photolithography
Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Additive Processes
Oxidation
Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Additive ProcessesDoping
Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)
Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon
Doping Methods1 Diffusion
Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C
It is governed by Fickrsquos Laws of Diffusion
Dopant ions bombarded into targeting substrate by high energy
Ion implantation are able to place any ion at any depth in sample
2 Ion Implantation
The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Additive Processes
Physical Vapor Deposition (PVD)
1 Evaporation
Thermal Evaporator
Deposition is achieved by evaporation or sublimation of heated metal onto substrate
This can be done either by resistance heating or by e-beam bombardment
The material to be deposited is transported from a source to the wafers both being in the same chamber
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Additive Processes
Physical Vapor Deposition (PVD)
2 Sputtering
Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target
Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Additive Processes
Physical Vapor Deposition (PVD)
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Additive Processes
Chemical Vapor Deposition (CVD)
All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film
Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc
How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate
Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)
Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Subtractive Processes
Dry Etching
1 Dry Chemical Etching
HF Etching
HF is a powerful etchant and hence highly dangerous
XeF2 Etching
2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride
Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Subtractive Processes
Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion
Dry Etching
Plasma Etching
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Subtractive Processes
Dry Etching
3 Deep Reactive Ion Etching (DRIE)
A very high-aspect-ratio silicon etch method (usually gt 301)
BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8
1048708 Energetic ions (SF6+) remove protective
polymer at the bottom trench
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Subtractive Processes
DRIE Etched Pillars
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Subtractive Processes
Wet Etching
Isotropic etchants etch in all directions at nearly the same rate
Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)
This results in a finite amount of undercutting
Isotropic Wet Etching
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Subtractive Processes
Wet Etching
Anisotropic etchants etch much faster in one direction than in another
Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )
KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt
Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen
Anisotropic Wet Etching
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Surface Micromachining
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Example
An insulin pump fabricated by classic MEMS technology
(Surface Micromachining)
1 Pumping membrane 2 Pumping chamber
3 Inlet 4 Outlet
5 Large mesa 6 Upper glass plate
7 Bottom glass plate 8 patterned thin layer (for improved fluidics)
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites
Si076Ge024 Si084Ge016 superlattice
2 m
Si Nanowire Array
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects
wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport
Bulk crystal
a
Free standing thin film
d
Thin film
Substrate
httpscsx01scehueswaporcojcharlascursodoctorado12
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Thin Film Applications
100 nm sputtered YSZ film for solid oxide fuel
cells
Amorphous Si TFT on a SiNx passivated polyimide foil
Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance
Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates
Gas sensing applications
Thin layers in electronic devices
httpwwwbuedumfgpdfTullerpdf
Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires
2 m
Si Nanowire Array
Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter
SiSiGe NanowiresAbramson et al JMEMS (2003)
Wu et al Nanoletters Vol 2 83 ndash 86 (2002)
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices
5 nm Si nanowire FET
Cui et al Nanoletters Vol 3 149 ndash 152 (2003)
Nanolaser from 100 nm CdSe nanowire
httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall
nanotubesropes bundles arrays Structure (chirality diameter) influences properties
Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity
Multi-wall carbon nanotube
httpwwwaiporgmgrpng2003186htm
Armchair
Zigzag
Chiralhttpphysicsweborgarticleworld11191
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited
for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties
independent of diameter and of layers
SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si
atoms
Boron nitride nanotubes
adopt various shapes
(red=boron blue=nitrogen)
httppubsacsorgcentopstory79127912notw1html
SiC nanotubes grown at NASA
Glenn
httpwwwgrcnasagovWWWRT200250005510lienhardhtml
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
NanoparticlesQuantum Dots
ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure
as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples
Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light
Photography ndash small colloidal silver particles for image formation
1 A
1 nm
10 nm
102 nm
103 nm
104 nm
105 nm
molecules
nanoparticles
Radius of particle or cluster
bulk
quantum dots
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
NanoparticlesQuantum Dots
Metalic nanoparticles
wwwavekacom
Si nanoparticle single-crystal hexagonal shape
Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)
Gradient of gold nanoparticles on a silica surface
httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they
manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular
markers) nanoparticles are coated and functionalized with antibodies
oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities
Organic + organic Organic + inorganic Inorganic + inorganic
Nanoparticle or nanowire or nanotube + matrix material
Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers
Polymer containing 40 wt silica particles for use as a gas
separation membrane
TiO2-oligonucleotide nanocomposites hybridized with
DNA for cellular manipulation
Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)
Merkel et al Science Vol 296 519 ndash 522 (2002)
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
What can we measure
structure
properties
composition
crystallinitystrain defects
mechanicalelectricalopticalmagnetic
thermal
atomic speciesconcentration
diffusionsegregation
tensile strength
hardness
yield
modulus of elasticity
failure
stiffness
conductivity
electron states
carrier densityband gap
conductivity
Seebeck coefficient
specific heat
susceptibilitymagneto-resistance
dielectric constant
surface roughness
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light
Can we use something other than light and lenses
AFM basic components Tip (lt~10 nm diameter) on a
cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software
Lateral resolution 01 nm Vertical resolution 002 nm
Image of graphite using an AFM
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
AFM modes
Tip angstroms from surface (repelled)
Constant force
Highest resolution
May damage surface
contact modecontact mode non-contact modenon-contact mode
Tip hundreds of angstroms from surface (attracted)
Variable force measured
Lowest resolution
Non-destructive
tapping modetapping mode Intermittent tip contact
Variable force measured
Improved resolution
Non-destructive
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
AFM images
Cu Nanowires
R Adelung et alR Adelung et al
Ge islands on Si
K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-
Resolution ~5 nm
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
SEM and AFM images
SEM Cu Nanowires
AFM Cu Nanowires
R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
sample
Transmission Electron Microscopy
A TEM works like a slide projector but with e- instead of light
TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-
e- beam focused via lensesBeam strikes sample and some e- are
transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking
out high-angle diffracted e- Image passed through lenses and
enlargedWhen image hits phosphor screen light
is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst
lens
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
TEM of Ge on SiTEM of Ge on Si
HRTEM Cross-Sectional View
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst
TEM comparison
Standard TEM High resolution TEM
Courtesy of F ErnstCourtesy of F Ernst