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

Abstract

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 H 2O 2, 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.