A density functional theory study of epitaxial graphene on the (3×3)-reconstructed C-face of SiC

We study the electronic properties of epitaxial graphene on the (3×3)-reconstructed SiC(0001¯) plane within the density functional theory. Our results show that the interface interaction is inherently weak. The first graphene layer above the substrate is almost planar and sp2-hybridized. The substrate's contribution in the low-energy electronic spectrum is present through (a) interface states deriving from SiC surface atoms with bands that disperse around the Dirac point, (b) a mild n-type doping, and (c) a ∼20 meV band-gap opening. Substrate interference is, therefore, an issue also in the case of graphene grown on the C-face of SiC.