Talk Wires

8/13/2019 Talk Wires

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1D Objects: Nanowires

There are many ways tomass-produce nanowires

by self-assembly


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Wu et al., Chem. Eur. J. 8, 1261 (2002)

Silicon Nanowire Growth

Si(111) substrate


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Wu and Yang, JACS 123, 3165 (2001)

Catalytic Nanowire Growth of Ge by Precipitation from Solution in Au


4/22Peidong Yang et al., Science 292, 1897 (2001) and Int. J. of Nanoscience 1, 1 (2002)

ZnO Nanowires Grown by Precipitation from a Solution

SEM images of ZnO nanowire arrays grown on sapphire substrates. A top view of the well-faceted hexagonal nanowiretips is shown in (E). (F) High-resolution TEM image of an individual ZnO nanowire showing its growth direction.

For the nanowire growth, clean (110) sapphire substrates were coated with a 10 to 35 thick layer of Au, with orwithout using TEM grids as shadow masks.


5/22Ohgai, , Ansermet, Nanotechnology 14, 978 (2003)

Cu/Co Nanowires Grown by

Electroplating into Etched Pores


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Carbon Nanotubes

Patterned Growth from Catalytic Metals (Ni, Co, Fe,)


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Lefebvre et al., PRL 90, 217401 (2003)

Free-Standing Nanotubes between Pillars

Wiring by Self-Assembly ?


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Indexing of Nanotubes

21 aaC mn

r +=

armchair

n=m

zigzag

m=0

chiral

nm

Circumference:


9/22Review: Cees Dekker, Physics Today, May 1999, p. 22.

- Bands Quantized along the Circumference of a Nanotube

CalculatedDensity ofStates

ScanningTunnelingSpectroscopy(STS)


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Bachilo, ... , Weisman,Science 298, 2361 (2002)

Separate Optical Spectra for

Nanotubes with Different

Diameter and Chirality

I l ti N t b i id Mi ll


11/22O'Connell,... Weisman, Smalley, Science 297, 593 (2002)

Isolating Nanotubes inside Micelles

sodiumdodecylsulfate(SDS)


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Carbon Nanotubes: Energy Scales

~10 eV Band Width (-Band)

~0.5 eV Quantization along the Circumference (k=1/R)

~0.1 eV Coulomb Blockade (Charging Energy ECoul=eQ/C) : : Quantization along the Axis (k=2/L)

:~0.001 eV Luttinger Liquid (Many-Electron Coupling)


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QuantizedConductance

Dipping nanotubes intoa liquid metal electrode

Conductance Quantum:G0= 2e2/h 1/13k

(Factor 2 for spin

,

)Each wavefunction(= band = channel)contributes G0.

Expect 2G0in nanotubes(two identical bands),but symmetry breakingcauses a reduction to

1G0(one band is lower).

Li it f El t i


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Conductance per Channel: G= G0T G0=2e2/h T1

Energy to switch one bit: E = kBTln2

Time to switch one bit: t = h / E

Energy to transport a bit: E = kBT /c d Distance d

Limits of Electronicsfrom Information Theory

Birnbaum and Williams, Physics Today, Jan. 2000, p. 38.Landauer, Feynman Lectures on Computation .


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Wire Arrays at Surfaces


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17/22

Stepped Silicon Surfaces as Templates

80 nm15 nm6 nm

Tobacco Mosaic Virus


18/22

SteppedSi(111)7x7

Straight steps

because of thelarge 7x7 cell.Large kinks

cost energy.

1 kink in 20000atoms, spacing

still imperfect.15 nm


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Period = 5.7 nmRNase = 4nm x 6 nm

Atomic Precision below 10 nm

Matched to Small Proteins

In Pursuit of the Ultimate Storage Medium


20/22

In Pursuit of the Ultimate Storage Medium

1 Bit = 1 Atom

10 m

10 nm

CD-ROM

Silicon Surface

Density x106

Track spacing

5 Atom Rows

Bennewitz et al.,Nanotechnology13, 499 (2002)


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Manymetalscatalyzechains

on Si(111)at ~1/5monolayercoverage


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Variable ChainSpacing/Coupling

Graphitic

HoneycombChain 1DAu

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