Initial oxidation process on Si(001) is studied by means of surface differential reflectance (SDR). At high temperatures (820 and 920 K), time-course of the reflectance spectra (ΔR/R) was found to represent the oxygen coverage, and to discriminate the two growth modes, Langmuir-type adsorption and two-dimensional island growth. At room temperature, significant photon energy dependence was observed in the time-course profiles of ΔR/R. This indicates that the partial oxygen coverage at the different adsorption sites may be estimated from them. From the temperature-dependence of the spectral time-courses, two components in the SDR spectra at 1.4 eV and 2.6 eV, were separately analyzed. Different activation energies were obtained from the Arrhenius plots. The results were discussed in terms of the possible assignments of these components.
