Hydrogenated and oxidized vicinal Si(001) surfaces investigated by reflectance-difference spectroscopy

We have investigated the effects of hydrogenation and oxidation on the surface-induced optical anisotropy (SIOA) of vicinal Si(001) as measured by reflectance-difference (-anisotropy) spectroscopy (RDS/RAS). By considering several vicinal Si(001) surfaces we better isolate terrace from step-induced contributions. For double-domain surfaces etched by HF or oxidized by H2O2, the RD response has an energy-derivative-like shape and can be characterized by three main features, the first near 3.4 eV and a second and third around 4.3 eV. These energies are near those of the (E(0), E(1)) and E(2) interband critical points of bulk silicon. The magnitudes of these peaks vary strongly with offcut angle suggesting that there is a strong step-induced contribution to the SIOA. Two of these features are affected by a change of the surface species, which indicates that the species bonded to the steps are changing. The RD response obtained by exposing atomic H to a double-domain surface hydrogenated by HF is similar to that obtained by exposing a clean single-domain surface to atomic hydrogen.