Rotations of silica tetrahedrons in first oxide layer on Si(1 0 0): A quantum chemical study

Optimization of large SiO2/Si clusters was carried out by a semiempirical method. The major result is that the compressive stress which is generated during oxidation induces an organized rotation of silica tetrahedrons. For the first oxidized layer, the tetrahedrons rotate by 20° around the axis parallel to the dimer. In order to obtain reliable energies and density of states (DOS), this model was also computed with an ab initio Hartree–Fock method employing periodic boundary conditions. Using a network connectivity concept, we explain how the influence of a chemical species on the silicon oxidation process depends on the valency of the species. A new technology computer aided design (TCAD) model of oxidation is proposed on the basis of these results.