All-optical determination of initial oxidation of Si(100) and its kinetics

By comparison of measured and ab initio calculated surface optical spectra we demonstrate that two main oxidation processes initially occur after dissociation of oxygen molecules, forming in both cases Si-O-Si entities: (i) breaking of Si dimers by incorporation of oxygen atoms; (ii) incorporation into the silicon backbonds. The kinetics up to half-monolayer coverage is determined, and explained in terms of Langmuir-like adsorption mechanisms with different probabilities.