Gap state formation during the initial oxidation of Si(100)-2x1

High-resolution electron energy loss spectroscopy and photoluminescence measurements have been used to follow the formation of gap states during the initial oxidation of Si(100)-2x1 at room temperature. We find strong indications that gap states are already induced after the adsorption of 0.002 L of molecular oxygen on Si(100)-2x1. It is demonstrated that prolonged exposures of clean and dehydrogenated oxide films on Si(100) to H2O at room temperature decrease the density of gap states significantly. (C) 2000 American Institute of Physics. [S0003- 6951(00)03449-5].