Theoretical study of (111) A surface of cubic silicon carbide

Abstract

Ab initio calculations of the atomic and electronic structure of 4 variants of the 3С-SiC(111)-(2√3 х 2√3)R30^о Si- terminated surface: initial, relaxed, reconstructed and relaxed after reconstruction have been performed for the first time. In the layered superlattice approximation, the surface was modeled by a system of the thin films with the thickness of 12 atomic layers (~1,6 nm) and separated by vacuum gaps of ~1,6 nm. To close the carbon dangling bonds on the opposite side of the film, 12 hydrogen atoms were added. Ab initio calculations were carried out using the program QUANTUM ESPRESSO, based on the density functional theory. In each of the variants, the equilibrium coordinates of the Si and C atoms of the upper four layers were determined. It was shown that the reconstruction leads to the splitting of layers. The results of our previous works and experimental data have shown that such splittings are inherent in the reconstruction of surface (111) in crystals with sphalerite structure. The band structures of 4 variants of slabs and full and layer-by-layer electronic densities of the states have been calculated and analyzed. It turned out that the real surface has a metallic conductivity.