graphene oct15th2010 moeez shem.ppt
TRANSCRIPT
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Graphene- Electric Properties
Shpyrko Research Group. UCSDOct 15th 2010Jong Woo Kim
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MotivationMotivation
• 2010 Nobel Prize for Physics
Physicists Konstantin Novoselov (left) and Andre Geim of University of Manchester
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History History
Theory of GrapheneP. R. Wallace
Isolated atomic layer from graphite A. K. Geim, K. S. Novoseolv
Massless Dirac equation of Graphene G. W. Semenoff
[Fabrication techniques]CVD Epitaxial growth on SiCChemical method by reducing agent
1947 1984 2004 2005
Massless Dirac Fermion Proved A. K. Geim, K. S. Novoseolv Y. Zhang, P. Kim
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Graphene?Graphene?
Fullerene(Bucky ball*)
Nanotube Graphene
* Nobel Prize in Chemistry 1996
0D 1D 2D
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Graphene?Graphene?
• Thin, mechanically strong, transparent and flexible conductor • Can be used in touch screen, light panel, solar cells (ITO) and
flexible display
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Electrical Properties Electrical Properties
• Verified Exotic Electrical Behaviors – Dirac Fermions with zero effective mass– Half-Integer Quantum Hall effect
• Novoselov, et al. Nature (2005), Zhang et al, Nature (2005)
– Klein Tunneling• A. F. Young and P. Kim, Nature (2009)
• Revisited topics – Quantum dot, p-n junction, nanoribbons, quantum point
contacts, magnetotransport near neutrality point
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• Exceptional Band Structure
Dirac Point
Brillouin Zone
Dirac Cone
Electrical Properties Electrical Properties
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• Unique Band Structure
Energy
Momentum
Energy
Momentum
Band GapElectrons in usual solids(Schrodinger equation)
Electrons in graphene(Dirac equation)
Electrical Properties Electrical Properties
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• Hall Effect – Electric field developed across two faces of conductor in the direction j × H
when a current j flows across a magnetic field H
• Quantum Hall Effect– Discovered in 1980– σxy =νˑe2/h (ν is an integer)
– At low temperature and strong magnetic field
• Half-integer quantum Hall effect– σxy =4ˑ(N+ ½)e2/h (N is an integer)
– At room temperature (300K)
Novoselov et al, 2005
Electrical Properties Electrical Properties
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• Klein tunneling– In 1929, Oscar Klein– A tunnel barrier can become fully transparent for normal incidence of
massless particles– Test in graphene was suggested by Katsnelson, Geim and Noveselov in
2006 and verified by Young and Kim in 2009
Electrical Properties Electrical Properties
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• Novoselov et al. Nature. 438, 197-200 (2005)• Zhang et al. Phys. Lett. 86, 073104 (2005)• A. F. Young et al. Nature Phys. 5, 222 (2009)• A. K. Geim. Science Vol. 324. no. 5934, pp. 1530 – 1534(2009)
ReferenceReference