The temperature dependence of monolayer oxidation on Si(001)-(2 × 1) studied with surface differential reflectance spectroscopy

The initial process of dry oxidation on a Si(001)-(2 X 1) surface was investigated using surface differential reflectance (SDR) spectroscopy. The photon energy dependence of the difference spectra and their time courses during oxidation were analysed. It is suggested that oxidation processes at different adsorption sites can be identified from the SDR spectra. The temperature dependence of the time courses was investigated in order to obtain the activation energies. Finite activation energies for monolayer oxidation were found in the temperature range of 623-823 K, corresponding to Langmuir-type adsorption. The photon energy dependence of the activation energies could reflect the involvement of different reaction processes. Chemical reaction processes of both oxygen and silicon during oxidation in a monolayer regime are discussed.