Optical Properties of the Interface between Si and Its Thermally Grown Oxide

The in situ optical properties of the interface between Si and its thermally grown oxide, deduced over the spectral region between the visible and the near-ultraviolet by analysis of spectroscopic ellipsometric data, are characteristic of a (7\ifmmode\pm\else\textpm\fi{}2)-\AA{} region of atomically mixed Si and O of average stoichiometry Si${\mathrm{O}}_{0.4\ifmmode\pm\else\textpm\fi{}0.2}$. The results are incompatible with either microroughness or an abrupt transition from Si to Si${\mathrm{O}}_{2}$, but rather support a graded transition region.