Potential Applications for Graphene Devices in Nanoelectronics
Graphene nanoelectronics from ab initio theory
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APS -- March Meeting 2011 Graphene nanoelectronics from ab initio theory Jesse Maassen, Wei Ji and Hong Guo Department of Physics, McGill University, Montreal, Canada QuickTime™ and a TIFF (LZW) decompres are needed to see thi
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Graphene nanoelectronics from ab initio theory. Jesse Maassen , Wei Ji and Hong Guo Department of Physics, McGill University, Montreal, Canada. Motivation (of studying a graphene/metal contact). - PowerPoint PPT Presentation
Transcript of Graphene nanoelectronics from ab initio theory
APS -- March Meeting 2011
Graphene nanoelectronics from ab initio theory
Jesse Maassen, Wei Ji
and Hong Guo
Department of Physics,
McGill University, Montreal, Canada
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
APS -- March Meeting 2011
Motivation(of studying a graphene/metal contact)
Graphene has interesting properties (i.e., 2D material, zero gap, linear dispersion bands, …).
For electronics, all graphene sheets must unavoidably be
electrically contacted to a metal (source/drain).
Can the graphene/metal interface largely influence the global response of the device?
Subject of much experimental and theoretical research.
APS -- March Meeting 2011
Experimental works:
Nature Nanotechnology 3, 486 (2008) Phys. Rev. B 79, 245430 (2009)
Photocurrentexperiments
Motivation(of studying a graphene/metal contact)
APS -- March Meeting 2011
Experimental works:
Nature Nanotechnology 3, 486 (2008) Phys. Rev. B 79, 245430 (2009)
Photocurrentexperiments
Motivation(of studying a graphene/metal contact)
APS -- March Meeting 2011
Our goal
Parameter-free
transport calculation
of a graphene /
metal interface
APS -- March Meeting 2011
Theoretical method
• Density functional theory (DFT) combined with nonequilibrium Green’s functions (NEGF)1
• Two-probe geometry under finite bias
NEGF
DFT
HKS
1 Jeremy Taylor, Hong Guo and Jian Wang, PRB 63, 245407 (2001).
SystemLeftlead
Rightlead
- +
Simulation Box
+
-
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Atomic structure
Which metals? What configuration at the interface?
Cu, Ni and Co (111) have in-place lattice constants that almost match that of graphene (PRL 101, 26803 (2008)).
Found most stable configuration (1stC on metal, 2ndC on hollow site).
After relaxation
Metal
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Appl. Phys. Lett. 97, 142105 (2010)
Graphene-metal interface
Bandstructure of hybrid
graphene | Cu(111) system
Graphene states in black Weak hybridization n-type graphene
Metal
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Graphene-metal interface
Double minimum T.
T almost perfectly described by pure graphene at TMIN.
Appl. Phys. Lett. 97, 142105 (2010)
Transport properties:
graphene | Cu(111) junction
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EF
k
E
Graphene-metal interface
Transport properties:
graphene | Cu(111) E = 0.2 eV
Tra
nsm
issi
on
kx
kz
Momentum filteringk
Nano. Lett. 11, 151 (2011)
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Graphene-metal interface
One Dirac point pinned, while other moves with V.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Peak in conductance doping level of graphene
Appl. Phys. Lett. 97, 142105 (2010)
Transport properties:
graphene | Cu(111) junction
APS -- March Meeting 2011
Graphene-metal interface
Band structure : graphene-Ni(111) system
Strong hybridization with metal
No more linear bands
Spin-dependent band gaps
Nano. Lett. 11, 151 (2011)
: A-site C(pz): B-site C(pz)
: Ni(dZ2)
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Graphene-metal interface
Nano. Lett. 11, 151 (2011)
Transport properties : graphene-Ni(111) system
APS -- March Meeting 2011
Graphene-metal interface
Transport properties : graphene-Ni(111) system
Nano. Lett. 11, 151 (2011)
APS -- March Meeting 2011
Graphene-metal interface
Transport properties : graphene-Ni(111) system
• Spin-dependent band gaps large spin filtering
Nano. Lett. 11, 151 (2011)
APS -- March Meeting 2011
Performed a parameter-free calculation of electronic transport through a graphene/metal interface.
Cu merely n-dopes the graphene resulting in:
• Double T minimum
• Similar trends for Al, Ag, Au & Pt
• Simple modeling
Ni & Co create spin-dependent (pseudo-) band gaps in
graphene. Large spin injection efficiencies ~80%.
Graphene-metal interface
SUMMARY
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Thank you !
Questions?
Computation facilities: RQCHP
Financial support: NSERC, FQRNT and CIFAR
