Core-electron x-ray photoelectron spectroscopy of the evolution of nearly flat, terraced, homogeneously H-terminatedSi(100)during prolonged exposure to air at room temperature

An experimental study based on x-ray photoelectron spectroscopy of room-temperature oxidation in air of nearly flat, terraced, hydrogen terminated (100) silicon has been carried out. The oxidation kinetics are characterized by two temporal domains, essentially associated with the formation of the substoichiometric oxide and for its transformation into the stoichiometric oxide: the substoichiometric oxide grows (with kinetics that may described in terms of an autocatalytic process) showing saturation at about $5\ifmmode\times\else\texttimes\fi{}{10}^{14}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$, while the stoichiometric oxide grows following a time logarithmic law. The entire process is characterized by the increase of a feature, with binding energy shifted by about $+0.3\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ with respect to that of elemental silicon, attributed to silicon atoms or clusters embedded in the growing oxide.