Electronic states of Si(100) reconstructed surfaces

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Abstract
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.