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Graphene oct15th2010 moeez shem.ppt


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Graphene oct15th2010 moeez shem.ppt

  1. 1. Graphene - Electric Properties Shpyrko Research Group. UCSD Oct 15th 2010 Jong Woo Kim
  2. 2. Motivation • 2010 Nobel Prize for Physics Physicists Konstantin Novoselov (left) and Andre Geim of University of Manchester
  3. 3. History Massless Dirac equation of Graphene Massless Dirac Fermion Proved A. K. Geim, K. S. Novoseolv Y. Zhang, P. Kim G. W. Semenoff 1947 1984 Theory of Graphene P. R. Wallace 2004 2005 Isolated atomic layer from graphite A. K. Geim, K. S. Novoseolv [Fabrication techniques] CVD Epitaxial growth on SiC Chemical method by reducing agent
  4. 4. Graphene? Fullerene (Bucky ball*) 0D Nanotube * Nobel Prize in Chemistry 1996 1D Graphene 2D
  5. 5. Graphene? • Thin, mechanically strong, transparent and flexible conductor • Can be used in touch screen, light panel, solar cells (ITO) and flexible display
  6. 6. 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
  7. 7. Electrical Properties • Exceptional Band Structure Dirac Cone Dirac Point Brillouin Zone
  8. 8. Electrical Properties • Unique Band Structure Energy Band Gap Electrons in usual solids (Schrodinger equation) Momentum Energy Electrons in graphene (Dirac equation) Momentum
  9. 9. Electrical Properties • 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
  10. 10. Electrical Properties • 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
  11. 11. Reference • • • • 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)