INTRODUCTION TO NANOSCIENCE

AND NANOTECHNOLOGY

PHYS.472

Prof. Ali S. Hennache

Al-Imam Muhammad Ibn Saud Islamic University

Faculty of Sciences

Department of Physics

ASH/AIMISIU/CS/DP/RUH/05.06.2015/3.15PM/KSA

The course content has been structured to help the

student achieve the following objectives:

1. To gain an understanding of the principles of

nanotechnology; characterization of nano structured

materials; and tools and equipment for producing

and assembling at the nano scale.

2. To acquire experience in the use of equipment used in

nanotechnology .

3. To cultivate interest in the research and development

of nanotechnology for future advancement of the

career.

4. Discuss nanomaterials effects on medicine ,

environmental ,renewable energy, electronics etc....

Course Objectives /Outcomes

Reference Materials

1. Ratner, D. & Ratner, M. (2003). Nanotechnology: A

gentle introduction to the next big idea. New

Jersey: Pearson Education Inc, ISBN: 0131014005.

2. Charles P. Poole Jr. and Frank J. Owens (2003).

Introduction to Nanotechnology, Wiley-

Interscience , 1 st edition, ISBN-10: 0471079359

3. John F Mongillo (2007), Nanotechnology 101,

Greenwood Press, Westport, CT, ISBN: 0313338809.

4. Gabor L. Hornyak, H.F. Tibbals, Joydeep Dutta, and

John J. Moore (2009). Introduction to Nanoscience

and Nanotechnology, CRC Press, Boca Raton, ISBN

10: 1420047795.

Grading Policies

Course grade will be based on the following

components:

•Midterm Examinations (2): 2x 20 = 40%

•Home assignments – Quizzes = 15%

•Class participation = 5%

•Final Examination = 40%

ASH/AIMISIU/CS/DP/RUH/09.06.2015/KSA.6.44PM

The Exam Schedule for the

Summer 2015 Term

• Midterm Examination No.01 (20 marks)

MONDAY 22nd June 2015 @ 10.00AM

• Midterm Examination No.02 (20marks)

THURSDAY 02nd July 2015 @ 10.00AM

ASH/AIMISIU/CS/DP/RUH/09.06.2015/KSA.6.44PM

• QUIZ No.01 (5 marks)

TUESDAY 16th June 2015 @ 11.00AM

PHYS. 472

INTRODUCTION

TO

NANOTECHNOLOGY

Prof. Dr. Ali S. Hennache Department of Physics

College of Sciences

ASH/AIMISIU/CS/DP/RUH/05.06.2015/3.15PM/KSA

Content

Chapter 1- Introduction to nanoscience and nanotechnologies

Chapter 2- Principal synthesis techniques of nanosystems

Chapter 3- Quantification

Chapter 4- Porosity and texture of materials

Chapter 5- Nanomaterials and devices

Chapter 6- Deposition and etching of thin films

Chapter 7- Characterization techniques

Chapter 8- Devices based on thin films

Nanomaterials characterization

* What SEM and AFM are good for?

* What is the Atomic Force Microscopes Contribution

to Nanotechnology?

* What is Spectroscopy?

Background and History

The Scanning Tunneling Microscope (STM) was invented by G. Binnig and H. Rohrer, for which they were awarded the Nobel Prize in 1984

A few years later, the first Atomic Force Microscope (AFM) was developed by G. Binnig, Ch. Gerber, and C. Quate at Stanford University by gluing a tiny shard of diamond onto one end of a tiny strip of gold foil

Currently AFM is the most common form of scanning probe microscopy

Light microscope

(magnification up to 1000x)

to see red blood cells

(400x)

Using Light to See

The naked eye can see to about 20 microns

• A human hair is about 50-100 microns thick

Light microscopes let us see to about 1 micron

• Bounce light off of surfaces to create images

10

Scanning Probe Microscopes

Atomic Force Microscope (AFM)

A tiny tip moves up and down in response to the

electromagnetic forces between the atoms of the

surface and the tip

The motion is recorded and used to create an

image of the atomic surface

Scanning Tunneling Microscope (STM)

A flow of electrical current occurs between the tip

and the surface

The strength of this current is used to create an

image of the atomic surface

11

Atomic Force Microscopes

(AFM)

The Atomic Force Microscope

was developed to overcome a

basic drawback with STM -

that it can only image

conducting or semiconducting

surfaces. The AFM, however,

has the advantage of imaging

almost any type of surface,

including polymers, ceramics,

composites, glass, and

biological samples.

1. Laser – deflected off cantilever

2. Mirror –reflects laser beam to photo detector

3. Photo detector –dual element photodiode that measures differences in light intensity and converts to voltage

4. Amplifier

5. Register

6. Sample

7. Probe –tip that scans sample made of Si

8. Cantilever –moves as scanned over sample and deflects laser beam

Parts of AFM

• Conductive AFM (c-AFM)

• Photo-conductive AFM (pc-AFM)

• Kelvin Probe Force Microscopy (KPFM)

• Piezoresponse Force Microscopy (PFM)

• AFM Nanoindentation

• AFM surface manipulation

Atomic Force Microscopy (AFM)

A

Schematic of the AFM operation

A sharp tip at the end of a micro-cantilever is scanned over the surface

Mode Topography Information/ Feedback

contact Deflection

intermittent contact (tapping mode) Amplitude

non-contact Frequency

Laser

sample Cantilever with tip

Split

photodiode

Feedback

Z- piezo,

Piezo

drive

Usually optical feedback

but also

other feedback types

e.g. tuning fork FB

Because the atomic force

microscope relies on the

forces between the tip and

sample, knowing these forces

is important for proper

imaging. The force is not

measured directly, but

calculated by measuring the

deflection of the lever, and

knowing the stiffness of the

cantilever. Hook’s law gives F

= - kz, where F is the force, k

is the stiffness of the lever,

and z is the distance the 5

lever is bent.

Schematic of the AFM operation

Scanning Tunneling Microscope

(STM)

x

feedback

regulator

high voltage

amplifier

z

y

I

Negative feedback keeps the current constant (pA – nA ) by moving the tip up and down.

Contours of constant current are recorded which correspond to constant charge density.

probing tip

sample

xyz- Piezo -Scanner

Atomic Force Microscopy (AFM)

AFM STM

no requirements sufficiently conductive sample

atomic resolution possible atomic resolution standard

but hard to get

local electrical information local electrical information and

independent of topography topography not separable

Contact not well defined defined tunneling via single atom

Also mechanical information xxx

• Monitors the forces of

attraction and repulsion

between a probe and a

sample surface

• The tip is attached to a

cantilever which moves up

and down in response to

forces of attraction or STM

repulsion with the sample

surface

– Movement of the cantilever

is detected by a laser and

photo detector

Atomic Force Microscopes

Shading shows

interaction

strength

AFM tips and cantilevers are microfabricated

from Si or Si 3N 4. Typical tip radius is from a

few to 10s of nm.

An atomic force microscope (AFM) creates a

highly magnified three dimensional image of

a surface. The magnified image is generated

by monitoring the motion of an atomically

sharp probe as it is scanned across a

surface. With the AFM it is possible to

directly view features on a surface having a

few nanometer-sized dimensions including

single atoms and molecules on a surface.

This gives scientists and engineers an ability

to directly visualize nanometer-sized objects

and to measure the dimensions of the

surface features.

Why AFM?

MBE Ge on p Si(001) substrate

strain induced dewetting of surface

SiGe layer forms domes

1.5x1.5 µm AFM topography , z= 60 nm

Topography and electrical

conductivity Probed by AFM

The fundamental interaction at short

distances is the van der Waals

interactions, which are responsible for

the formation of solids, wetting, etc. At

distances of a few nm, van der Waals

forces are sufficiently strong to move

macroscopic objects such as AFM

cantilevers. Van der Waals interactions

consist of three components:

polarization, induction, and dispersion.

Polarization refers to permanent dipole

moments such as exist in water

molecules. Induction refers to the

contribution of induced dipoles.

Dispersion is due to instantaneous

fluctuations of electrons, which occur

at the frequency of light.

Measuring forces

- Used for Contact Mode, Non-contact and Tapping Mode AFM

- Laser light from a solid state diode is reflected off the back of the

cantilever and collected by a position sensitive detector (PSD). This

consists of two closely spaced photodiodes. The output is then

collected by a differential amplifier

- Angular displacement of the cantilever results in one photodiode

collecting more light than the other. The resulting output signal is

proportional to the deflection of the cantilever.

- Detects cantilever deflection <1A

Modes of operation

Modes of operation

Repulsive (contact)

At short probe-sample

distances, the forces are

repulsive

Attractive Force (non-

contact)

At large probe-sample

distances, the forces are

attractive

The AFM cantelever can be

used to measure both

attractive force mode and

repulsive forces.

Constant force is applied to the surface while scanning

Contact mode

Potential diagram showing the region

of the probe while scanning in

contact mode.

In contact mode the probe

glides over the surface.

Contact mode is typically used for scanning hard samples and when a

resolution of greater than 50 nanometers is required. The cantilevers

used for contact mode may be constructed from silicon or silicon

nitride. Resonant frequencies of contact mode cantilevers are typically

around 50 KHz and the force constants 8 are below 1 N/m.

Left: Bits on a compact disk.

Center: Image of a metal surface.

Right: Nano-particles on a surface

Contact mode images

The probe is vibrated in and out of surface potential. The modulated

signal can then be processed with a phase or amplitude demodulator.

Tapping mode • A cantilever with attached tip is oscillated at its resonant frequency

and scanned across the sample surface.

• A constant oscillation amplitude (and thus a constant tip-sample

interaction) are maintained during scanning. Typical amplitudes are

20- 100nm.

• Forces can be 200 piconewton (pN) or less .

• The amplitude of the oscillations changes when the tip scans over

bumps or depressions on a surface.

Vibrating mode AFM images.

Left: Silicon wafer.

Center: Cancer cells.

Right: Proteins.

Tapping mode images

Contact Mode Contact (DC and AC)

Force Modulation

Non-Contact Mode Non-Contact (AC)

Tapping (Intermittent contact)

Mode Tapping (AC)

Modes of AFM

AC=dynamic(tip is driven to oscillate), DC=static(no external oscillation on tip)

Easy sample

preparation

Accurate height

information

Works in vacuum, air,

and liquids

Living systems can be

studied

Limited vertical range

Limited magnification

range

Data not independent

of tip

Tip or sample can be

damaged

Advantages and Disadvantages

of AFM

Force Measurement The cantilever is designed with

a very low spring constant (easy

to bend) so it is very sensitive to

force.

The laser is focused to reflect off

the cantilever and onto the

sensor

The position of the beam in the

sensor measures the deflection

of the cantilever and in turn the

force between the tip and the

sample.

Other Types of Scanning Probe

Microscopy (SPM) Techniques Lateral Force Microscopy (LFM)

Frictional forces measured by twisting or “sideways” forces on cantilever.

Magnetic Force Microscopy (MFM) Magnetic tip detects magnetic fields/measures magnetic properties of

the sample.

Electrostatic Force Microscopy (EFM) Electrically charged Pt tip detects electric fields/measures dielectric

and electrostatic properties of the sample

Chemical Force Microscopy (CFM) Chemically functionalized tip can interact with molecules on the

surface – giving info on bond strengths, etc.

Near Field Scanning Optical Microscopy (NSOM) Optical technique in which a very small aperture is scanned very close

to sample Probe is a quartz fiber pulled to a sharp point and coated with

aluminum to give a sub-wavelength aperture (~100 nm)