Influence of stress and defects on the silicon-terminated SiC(001) surface structure

Using ab initio calculations, we have investigated the influence of stress and defects on the reconstruction of the (001) Si-terminated surface of cubic SiC. We find that an unstrained bulk is terminated by a p(2X1) reconstruction under tensile stress. This stress can be substantially relieved by the removal of dimers. Applying further tensile stress lowers the surface symmetry and leads to a c(4X2) pattern. The structural properties of this reconstruction are in very good agreement with recent measurements, suggesting that stress in SiC samples is responsible for the c(4X2) reconstruction observed experimentally. Furthermore, we have analyzed temperature and charging effects on the surface properties and made a comparative study of theoretical and experimental STM images. [S0163-1829(98)07019-2].