Isotopic substitution of Si during thermal growth of ultrathin silicon-oxide films on Si(111) inO2

Abstract

The transport of Si atoms during thermal growth of silicon-oxide films on silicon in dry ${\mathrm{O}}_{2}$ was investigated by isotopic substitution of Si. The experiment consisted of depositing a 7.6-nm-thick epitaxial layer of ${}^{29}\mathrm{Si}$ on a Si(111) substrate and determining the ${}^{29}\mathrm{Si}$ profiles, with subnanometric depth resolution, before and after oxidation in 50 mbar of dry ${\mathrm{O}}_{2}$ at 1000 \ifmmode^\circ\else\textdegree\fi{}C for 60 min. The results constitute an experimental confirmation of a widely held belief that Si does not diffuse through the growing oxide to react with oxygen at the gas/oxide interface, leaving ${\mathrm{O}}_{2}$ as the only mobile species.