The (100) silicon—silicon dioxide interface. I. Theoretical energy structure

The (100) Si—Si${\mathrm{O}}_2$ interface is characterized here in a systematic manner. A semiempirical tight-binding method is used to calculate the energy band structure and layer of density of states for (a) the free Si(100) surface, (b) the 2×1 reconstructed surface, (c) the chemisorbed surface (both atomic and molecular), and (d) the interface between a thin oxide and Si. New states, typical of Si—O bonds, are identified. For the interface and for chemisorption, the Si—O bond lengths and the Si—O—Si bond angles are varied and the calculations repeated. The results show little variation in the density of states, which indicates that the variations in the results arising from differences in the actual bond lengths and bond angles are negligible.