F. Varchon

Electronic Structure of Epitaxial Graphene Layers on SiC: Effect of the Substrate

A strong substrate-graphite bond is found in the first all-carbon layer by density functional theory calculations and x-ray diffraction for few graphene layers grown epitaxially on SiC. This first layer is devoid of graphene electronic properties and acts as a buffer layer. The graphene nature of the film is recovered by the second carbon layer grown on both the (0001) and (0001[over]) 4H-SiC surfaces. We also present evidence of a charge transfer that depends on the interface geometry. Hence the graphene is doped and a gap opens at the Dirac point after three Bernal stacked carbon layers are formed.

Electron states of mono and bilayer graphene on SiC probed by scanning-tunneling microscopy

We present a scanning tunneling microscopy (STM) study of a gently-graphitized 6H-SiC(0001) surface in ultra high vacuum. From an analysis of atomic scale images, we identify two different kinds of terraces, which we unambiguously attribute to mono- and bilayer graphene capping a C-rich interface. At low temperature, both terraces show

Quasiparticle Chirality in Epitaxial Graphene Probed at the Nanometer Scale

(\sqrt{3}\times \sqrt{3})

Quantum transport in chemically modified two-dimensional graphene: From minimal conductivity to Anderson localization

quantum interferences generated by static impurities. Such interferences are a fingerprint of

Dirac Particles in Epitaxial Graphene Films Grown on SiC

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Why Multilayer Graphene on 4H-SiC(000-1) Behaves Like a Single Sheet of Graphene

-like states close to the Fermi level. We conclude that the metallic states of the first graphene layer are almost unperturbed by the underlying interface, in agreement with recent photoemission experiments (A. Bostwick et al., Nature Physics 3, 36 (2007))

Rotational disorder in few-layer graphene films on 6 H − Si C ( 000 − 1 ) : A scanning tunneling microscopy study

Graphene exhibits unconventional two-dimensional electronic properties resulting from the symmetry of its quasiparticles, which leads to the concepts of pseudospin and electronic chirality. Here, we report that scanning tunneling microscopy can be used to probe these unique symmetry properties at the nanometer scale. They are reflected in the quantum interference pattern resulting from elastic scattering off impurities, and they can be directly read from its fast Fourier transform. Our data, complemented by theoretical calculations, demonstrate that the pseudospin and the electronic chirality in epitaxial graphene on SiC(0001) correspond to the ones predicted for ideal graphene.

Ripples in epitaxial graphene on the Si-terminated SiC(0001) surface

An efficient computational methodology is used to explore charge transport properties in chemically modified (and randomly disordered) graphene-based materials. The Hamiltonians of various complex forms of graphene are constructed using tight-binding models enriched by first-principles calculations. These atomistic models are further implemented into a real-space order-N Kubo-Greenwood approach, giving access to the main transport length scales (mean free paths, localization lengths) as a function of defect density and charge carrier energy. An extensive investigation is performed for epoxide impurities with specific discussions on both the existence of a minimum semiclassical conductivity and a crossover between weak to strong localization regime. The 2D generalization of the Thouless relationship linking transport length scales is here illustrated based on a realistic disorder model.

Graphene-substrate interaction on 6 H -SiC ( 000 1 ¯ ) : A scanning tunneling microscopy study

We report on the transport and structural properties of graphene layers grown epitaxially on hexagonal SiC. Experimentally, the charge carriers in epitaxial graphene are found to be chiral and the band structure is clearly related to the Dirac cone. To lowest order, epitaxial graphene appears to consist of stacked graphene sheets; the first layer is highly charged with the others carrying much lower charge.