Kinetics of initial oxidation of the Si(111)-7 × 7 surface near the critical conditions

Abstract

The kinetics of the initial oxidation of Si(111)-7 × 7 by oxygen at pressures from 5 × 10 −9 to 1 × 10 −6 Torr are investigated with optical second-harmonic generation at surface temperatures near T tr, where T tr is the transition temperature from oxide growth to Si etching. The initial reactive sticking coefficient, obtained from the rate of oxide growth, decreases gradually to zero at T tr with increasing temperature. The pressure dependence of the reaction rate constants derived by using a precursor model shows the key role of the interaction in the layer of chemisorbed precursor species for initial silicon oxidation near T tr. It is shown that the pressure and temperature dependence of the reaction rate constants of the precursor species determines the boundary for oxide nucleation.