The structural models for the (2\sqrt {3}\times 2\sqrt {3})\mathrm {R}30^{\circ} reconstructions of 3C-SiC(111) and 6H-SiC(0001) surfaces

We propose a double-trimer model and a single-trimer model for reconstructions observed on the surface of the 3C-SiC(111) island and the 6H-SiC(0001) surface, respectively. We study their atomic and electronic structures by using first principles calculations within density-functional theory. The total energy calculations indicate that the double-trimer model and the single-trimer model are energetically more favourable than the previously reported DV model and Tri-Ad model, respectively. The simulated scanning tunnelling microscopic images for these two models agree fairly well with the experimental observations. The surface energy band structures of the single-trimer model and the Tri-Ad model were compared, which might provide a criterion for the further discrimination of the exact models by experimental evaluation.