Theoretical Study of Oxygen Radicals Impacting Hydrogen-Terminated Silicon Surface

摘要

The total electronic energies of the hydrogen-terminated Si surface with various oxygen species are calculated to study oxidation process of the Si surface. First, we investigated the adsorption processes over the hydrogen-terminated Si(111) surface by oxygen species, the ~1O and ~3O radicals, the ~2O~+ cation, the ~2O~- anion, and ~3O_2 molecule. As a result, ~3O_2 molecule was repelled while other species are attracted when they approach the Si surface to form the Si-O-Si bond. Next, we calculated the diffusion process of the oxygen species (~1O, ~3O, and ~2O~- species) into the Si lattice. If the lattice structure of the Si crystal is fixed in such a way that the stress in the lattice is allowed to remain, these oxygen species are easy to invade into the crystal and to diffuse. These theoretical model results will be discussed in relation to the real oxidation processes. In particular, recent experimental results on the stress-preserving oxidation of Si surface by ozone due to Ichimura could be considered the partial realization of our theoretical prediction.