Keywords: electronic properties, epitaxial graphene, silicon carbide, graphite, Dirac electrons, STM, magneto-optics, quantum Hall effect, weak localisation, nanotechnology, rotational stacking sequence
Electronic properties of epitaxial graphene
It has been known for almost 25 years that high temperature treatment of polar faces of SiC crystals lead to the graphitisation of the surface as a consequence of Si preferential sublimation. The group of Walt de Heer in Atlanta has proposed to use this procedure to obtain macroscopic multilayer graphene samples. This has lead to a renewal of interest for the study of the graphitic layers grown on the SiC surfaces. Due to the polar nature of the material, the 6H(4H)-SiC substrate present two non-equivalent surfaces: the (0001) is known as the Si face, and the (000-1) one is the C face. It turns out that the structure and the properties of the multilayer graphene samples obtained on those two surfaces are rather different. In particular the multilayer graphene samples grown on the C-terminated face presents electronic properties that are rather similar to those of monolayer graphene with very high mobility. This is shown by transport and optical experiments under high magnetic field. This surprising result is explained by the rotational stacking sequence, observed experimentally, which leads to an electronic decoupling as demonstrated by ab initio band structure calculations.