Electronic states of Si(100) reconstructed surfaces

The detailed electronic structures and geometries of Si(100) reconstructed surfaces are investigated by a self-consistent calculation with a norm-conserving nonlocal pseudopotential. We concentrate on the dimer model and on (2×{}1), p(2×{}2), and c(4×{}2) reconstructions which are simultaneously detected by recent scanning-tunneling-microscopy measurements. The optimized geometries of asymmetric (2×{}1) and c(4×{}2) systems are reached by minimizing the total energy. Present study shows that the c(4×{}2) system is the most favorable one at absolute zero temperature; moreover, the p(2×{}2) system can also be favored because the total-energy difference between c(4×{}2) and p(2×{}2) systems is relatively small. Both of them are much more stable than (2×{}1) buckled structure. The surface electronic structures of p(2×{}2) and c(4×{}2) systems are analyzed and understood based on the electronic structure of (2×{}1) asymmetric-dimer model. Both the surface band structures and optimized geometries of the present calculation are in reasonably good agreement with experiments.