▎ 摘　　要

We present an ab initio study on the structural and electronic properties of {0001}-(1 x 1) surfaces of 6H-SiC and of epitaxial graphene on top of the surfaces, respectively. The fully-relaxed structure of the Si-terminated (0001) surface is found to be almost identical to the sp(3) bonding geometry of the bulk 6H-SiC while that, of the C-terminated (000 (1) over bar) side is flattened to have mixed characteristics of sp(3) and sp(2) bondings. Both surfaces have ferromagentically-ordered surface states with indirect band gaps. When graphene is commensurately placed on top of the SiC{0001}-(1 x 1) surfaces, it opens a wide energy gap at. the Dirac point owing to strong covalent; bondings to the SiC surface and, thus, forms an insulating buffer layer. Graphene on top of the buffer layer is shown to have linear energy bands and to exhibit, a very small energy gap at the Dirac point clue to sublattice-symmetry-broken interactions between the buffer layer and graphene.