Oxidation Kinetics of Si(111) 7x7 in the Submonolayer Regime.

摘要

The kinetics of the initial oxidation of Si(111) 7x7 by O2 in the submonolayer regime was studied using laser-induced thermal desorption, temperature-programmed desorption, and Auger-electron spectroscopy. The results showed that the oxidation of Si(111) 7x7 by O2 was characterized by two kinetic processes. Initially, a rapid oxygen uptake step occurred that was followed by a slower growth process which asymptotically approached an apparent saturation oxygen coverage. The initial reactive sticking coefficient of O2(SO) on Si(111) 7x7 decreased with surface temperature from SO=O.2 at 200 K to SO-0.06 at 600 K. The observed decrease in SO suggested that the initial oxidation of Si(111) 7x7 was mediated by an O2 precursor species. Experiments wit preadsorbed hydrogen also demonstrated that the initial reactive sticking coefficient for O2 and the apparent saturation oxygen coverage were reduced as a function of increasing hydrogen coverage on the Si(111) 7x7 surface. This behavior indicated that the oxidation of Si(111) 7x7 requires free dangling bond sites. (js)