7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
1/16
Graphene &
Nanowires:
ApplicationsKevin Babb & Petar PetrovPhysics 141A PresentationMarch 5, 2013
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
2/16
What is a Nanowire? One-dimensional structure
o Diameter: 1-100 nanometers (10-9 m)
o Length: microns (10-6 m)
Exhibits crystal structureo Unlike quantum dots (0-dimensional)
Many different materialso Metals, semiconductors, oxides
Kevin Babb & Petar PetrovPhysics 141ASpring 2013 2
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
3/16
Features of Nanowires Smallest dimension which can transport charge
carriers (e-, h+)o Can act as both nanoscale devices and wiring
o Unique density of states
Controlled synthesiso Diameter, length, composition
o Electronic structure (band gap, doping)
Sizeo Quantum confinement
Present in some, absent in others
Unique magnetic & electronic properties
o Millions more transistors per microprocessor
o Probe microscopic systems (e.g. cells)
Kevin Babb & Petar PetrovPhysics 141ASpring 2013 3
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
4/16
Graphene Reminder Graphene is a 2-d from of
pure carbon
Band gap depends onstructureo
Large area monolayerso Bilayers
o Nanoribbons
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
5/16
Solar Cells Currently: silicon wafers, thin films
Application of graphene:o Transparent conducting electrodes
Robust, conductive, abundant
Cheaper than ITO
Application of nanowires:o Enhanced light trapping
o Efficient charge transport (1D)
Kevin Babb & Petar PetrovPhysics 141ASpring 2013 5
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
6/16
Graphene-NanowireSolar Cells
A new design:o Layer of graphene (transparent cathode)
o Conductive polymer (maintains integrity)
o ZnO nanowire layer (electron transport)
o PbS quantum dots (hole transport)
o Au layer (anode)
Efficiency approaches ITO-basedsolar cellso 4.2% conversion efficiency (5.1% for ITO)
o
Cheaper to produce
Kevin Babb & Petar PetrovPhysics 141ASpring 2013 6
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
7/16
Field Effect Transistors Challenges to scaling
o Lower transconductance
o Manufacturing difficulties
o Quantum effects
o Gate capacitance
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
8/16
Graphene FETs Challenges
o Low on-off ratios
o High graphene-electrode contactresistance
o Tradeoff betweenmobility and bandgap
Advantages
High roomtemperaturemobility
Thinner than
traditional MOSFETs
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
9/16
Nanowire FETs Advantages
o Many differentnanowires withdifferent properties
o High mobilityo Bottom up
synthesis
Challenges
o Integrating NW intocircuit
o Control of growthand dopants
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
10/16
Light-Emitting Diodes LEDs versus conventional lighting:
o Efficient: less heat, lower power consumption
o Long lifetime
o Cheap
o No mercury
How nanowires help:o Various geometries of p-n junctions available
Coaxial wires
Thin film/wire combinations
Crossed-wire junction arrays
o Unique carrier transport properties
Natural waveguiding cavities
o Improve extraction efficiency of light
High surface area improves conductivity
Kevin Babb & Petar PetrovPhysics 141ASpring 2013 10
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
11/16
Artificial Photosynthesis Simulate natural photosynthetic process
o Convert CO2 and H2O into fuels, O2
H2O oxidation
CO2 reduction
How nanowires help: photoelectrodeso High surface area for reaction sites
o High charge mobility due to small diameter
o Can be grown in large quantities
Kevin Babb & Petar PetrovPhysics 141ASpring 2013 11
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
12/16
Touch Screen Devices Graphene is strong, transparent, highly
conductive, and cheaper than traditionalITO
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
13/16
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
14/16
This is scalable!
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
15/16
Ultracapacitors Graphene
advantages:o High surface area to weight
ratio (2600 m2 /g)
o High conductivity
o Measured specific
capacitance 135 F/g
Uses:o Electric vehicles
o Backup powering
o High power capability
o Cell phones
7/27/2019 Graphene and Nanowires--Petar Petrov and Kevin Babb.ppt
16/16
References Physical Foundations of Solid State Devices, E. F. Schubert
Y. J. Hwang, et al., Nano Lett., 2012, 12, 16781682
A. Hochbaum, Chem. Rev., 2010, 110, 527546
H. Park, et al., Nano Lett., 2013, 13, 233-239
E. Lai, et al., Nano Res., 2008, 1, 123-128 D. Siburly, et al.,J. Phys. Chem, 2005, 109, 15190-15213
F. Schwarz, Nature Nanotechnology, 2010, 5, 487496
S. Bae, et al., Nature Nanotechnology, 2010, 5, 574578
M. Stoller, et al., Nano Lett., 2008, 8, 34983502 Y. Zhang, et al., Nature, 2009, 459, 820-823
Kevin Babb & Petar PetrovPhysics 141ASpring 2013 16
Top Related