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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
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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.
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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:
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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
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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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Stepped Silicon Surfaces as Templates
80 nm15 nm6 nm
Tobacco Mosaic Virus
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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
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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