Nanotechnology
Defining Dimension: Involves products and processes with
significant features 100 nanometers and smaller. (To be
listed in Merrill Lynch nanotechnology index, a company
must indicate in a public document that nanotechnology
initiatives are a significant component of their business
strategy)
Significant because of unusual properties:
Mechanical – very strong; new devices (e.g., motor)
Physics – new phenomena (e.g., metallic or semiconducting)
Chemical – Reactivity, tiny hollow structures (e.g., can carry
drugs into body)
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Nanotech examples
Uses demonstrated:
Electrostaically driven nanomotor (Alex Zettl, UCB Physics)
Field effect transistors and logic devices (Ph. Avouris,
Nano-Letters 16 Aug. 2001) – NOR gate, flip-flop memory
cell, ring oscillator)
Sensors (Nanometrix Co.) – hydrogen sensing by palladiumcoated silicon nanotube operating as an FET
Liquid repellent cloth
Cautions (research needed):
“Gray goo” – if nanotech replicating structures are made
they could take over the Earth
Nanostructures can pass through/around cells in the body
Nanostructures may clump in liquids and have limited uses
in environmental remediation, drug delivery
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Synthesis of Nanowires
(Some Examples)
Sunkara et. al.
Lieber et. al. Wang et. al.
Fukui et. al.
Yang et. al.
2 m
Islam et. al.
Xia et. al.
Busbee et. al.
Kamins et. al.
Cao et. al.
Samuelson et. al.
Meyyappan et. al. Gundiah et. al.
Ag, Au, Zn, InP, ZnO, Si, Ge, Si-Ge, SiGeC, GaAs, ZnS, GaN, InGaAs, In2O3 and other materials ….
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8. Nanoelectronics
Au
Source
Nanotube
1.4 nm
SiO2
Drain
 p-type transistor (no intentional doping)
 I(on)/I(off)~105
 High contact resistance
 Low transconductance
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R. Martel et al. Apple. Phys. Lett. 73, 2447 (1998)
Approved for Public Release, Distribution Unlimited
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Nanotube inverter
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Getting rid of metallic nanotubes to make semiconductor devices
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GE solar
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Nanobatteries
MEMS field applications require novel sources of power.
Nanobatteries
• Comparable energy densities to conventional batteries
• Can be integrated into MEMS during the fabrication process
• Variety of applications requiring minute power
Representation of a bio-nanobattery using modified
proteins for energy storage
Nanobattery Schematic utilizing
membrane pores to maintain electrolytes
Nanobattery using
droplets of
electrolytes on top
of “nanograss” to
generate power
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10. Nanomanufacturing
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Approved for Public Release, Distribution Unlimited
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Simultaneous Growth of Nanowires and
Connecting Electrodes
Metal on Si surface
Evaporation at 45o angle
[111]
Si
Si
SiO2
1. Metal deposition, metalsilicide formation
2. Growth of Nanowire
Saif
Islam
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3. Nanowire Bridge
et. al., Nanotechnology
15 (2004) L5–L8
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Connecting Nanostructures
Bridging Nanowires
Form trench and
deposit catalyst
Nanowire grows perpendicular
to (111)-oriented sidewall
Nanowire connects
to opposite sidewall
2 µm
2 µm
M. Saif Islam, S. Sharma, T. I. Kamins, and R. Stanley
Williams, Nanotechnology 15, L5-L8 (May 2004)
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2 µm
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Nano-Colonnades: Vertical
Integration
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Fabrication of NanoColonnades
(a) Catalysts deposition
(b) Nanowire growth
Top
electrode
Nanowire
Insulating
layer
Catalysts
Doped
epi-layer
Bottom electrode
Insulating layer
Insulating
layer
Nanocolonnades
Metal
contact
Metal
contact
(c) Nanowire bridging
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(d) With metal electrodes
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Natural Colonnades: Stalagmites
Top Electrode
Bottom Electrode
Colonnades form in both
ways in the mountain caves
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Linear I-V characteristics
1.0
0.7
Current (mA)
0.5
V
~40 NWs
0.2
R
0.0
-0.2
-0.5
-0.7
-1.0
-4
-2
0
2
4
Voltage (V)
I=~0.8mA to ~1.2mA
17/cm3
Doping
=
4x10
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Summary
• First demonstration of a practical
massively parallel self–assembly
technique for interconnecting NWs
Devices
•
Electrode of
doped Si
Electrode of
doped Si
Connections are single
crystal,
electrically ohmic and
mechanically robust
• A large array of nanoscale
sensors are fabricated using only
coarse optical lithography
FUTURE WORK
•Create junctions for diodes, LEDs, lasers,
transistors
•Grow GaAs and InP nanowires on Si
•Explore other novel device applications
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