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 $p(2\mathrm{}\times 1)$ 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 $c(4\mathrm{}\times 2)$ 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 $c(4\mathrm{}\times 2)$ 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.