Isotopic substitution of Si during thermal growth of ultrathin silicon-oxide films on Si(111) in O2

The transport of Si atoms during thermal growth of silicon-oxide films on silicon in dry O-2 was investigated by isotopic substitution of Si. The experiment consisted of depositing a 7.6-nm-thick epitaxial layer of Si-29 on a Si(111) substrate and determining the Si-29 profiles, with subnanometric depth resolution,before and after oxidation in 50 mbar of dry O-2 at 1000 degrees 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 O-2 as the only mobile species. [S0163-1829(99)10127-9].