Epitaxial graphene Claire Berger GATECH School of Physics

Epitaxial graphene Claire Berger GATECH- School of Physics, Atlanta CNRS-Institut Néel, Grenoble NIRT Nanopatterned Epitaxial graphite

Motivation : Carbon nanotube transistors

Motivation : Multiwalled carbon nanotubes are ballistic conductors at room temperature G (2 e 2/h) - L (µm) Nanotube fiber L V Quantized ballistic conductance T. Ando, T. Nakanishi and R. Saito J. Phys. Soc. Jpn. 67, 2857 (1998) “The absence of backward scattering is shown to be ascribed to Berry's phase which corresponds to a sign change of the wave function under a rotation of a neutrino-like particle* in the wave vector space in a two-dimensional graphite” *i. e obeying the Dirac-Weyl equation

Nanotube Electronic Structure 1 D metallic sub-bands Semiconducting Ntube EF

Band structure of graphene Linear dispersion Symmetry electrons - holes Pseudospin Chirality T. Ando, J. Phys. Soc. Jpn 67 (1998) 2857

Graphene ribbons Semiconducting or metallic ribbons Metallic ribbons Graphene ribbons should retain the essential properties of carbon nanotubes

Energy gap in exfoliated graphene ribbons from Philip Kim, Columbia University Gap Eg= E /(W-W*) E =0. 2 e. V. nm W*=16 nm M. Y. Han, B. Özyilmaz, Y. Zhang, P. Kim, Cond. Mat. 0702511

Epitaxial growth of graphene layers on 4 H-Si. C Thermal decomposition of Si. C at high temperature (~1400 o. C) - high vacuum after surface flattening by hydrogen etching A. Charrier et al. , J. Applied Physics 92, 2479 (2002) (0001) Si-face Si Si Si LEED 3 graphene layers graphite C Si. C (0001) C-face Graphene on Si. C By controling temperature, growth of 1 to ~100 graphene layers C. Berger et al. , Journal of Physical Chemistry B 108, 19912 (2004)