Statistical Cross-Linking at theSi(111)/SiO2Interface

Angle-resolved photoemission measurements of the Si $2p$ core level as a function of polar emission angle were carried out to investigate the atomic populations and depth distributions of Si in various oxidation states for a ${\mathrm{SiO}}_2$ film thermally grown on Si(111). The suboxide states including ${\mathrm{Si}}^{1+}$, ${\mathrm{Si}}^{2+}$, and ${\mathrm{Si}}^{3+}$ exhibit different depth distributions. Despite these differences, the results are consistent with a chemically abrupt interface. A simple model based on the statistical cross-linking of dangling bonds between a bulk-truncated Si and an amorphous ${\mathrm{SiO}}_2$ layer explains our observations.