Oxidation of silicon surfaces

Abstract

We have carried out theoretical studies (generalized valence bond) for chemisorbed O atom and O2 molecule on Si(111) surfaces using clusters of atoms to model the surface. For the perfect surface we find that O2 molecule binds to a single surface Si with an Si–O bond length of 1.68 Å (bulk SiO2RSi–O = 1.61 Å), an Si–O–O angle of 116 °, and an O–O bond distance of 1.32 Å. We have also calculated the shifts in the Si(2p) and O(1s) core level energies for chemisorbed O and O2 on the surface. The Si(2p) shift is +1.1 eV (higher binding energy) for the O atom and +1.5 eV for O2, in agreement with the shifts observed for low oxygen exposure by Spicer and co-workers.