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Initial reactive sticking coefficient of O2 on Si(111)-7 × 7 at elevated temperatures

1996; Elsevier BV; Volume: 351; Issue: 1-3 Linguagem: Inglês

10.1016/0039-6028(95)01260-5

1879-2758

A. A. Shklyaev, Takanori Suzuki,

Ion-surface interactions and analysis

Kinetics of the initial stage of oxide growth in the reaction of oxygen with Si(111)-7 × 7 at temperatures from room temperature to Ttr, and pressures from 5 × 10−9 to 2 × 10−7 Torr are investigated with optical second-harmonic generation, here temperature from oxide growth to Si etching without oxide growth. At a fixed pressure, the initial reactive sticking coefficient (S0), obtained from the rate of oxide growth, decreases with increasing temperature to S0=0 at Ttr. We have found that the initial reacti sticking coefficient depends on the O2 pressure. At temperatures above 320°C, the whole temperature dependence of S0 is situated in the region of higher temperatures for higher O2 pressures (Pox). Moreover, an additional bend in the temperature dependence of S0 is observed for Pox>1 × 10−8 Torr near Ttr. A precursor-mediated adsorption model involving the reaction of formation is considered. The parameters of this model, obtained from the best fits to the experimental data, show that oxide growth rate constant increases and volatile SiO formation rate constant decreases as a function of O2 pressure. At zero oxide coverage, the pressure dependence of the reaction rate constants is suggested to originate from interaction in the layer of the chemisorbed precursor species, whose coverage depends on the O2 pressure. The volatile SiO formation is described by a three-step sequential two-channel process through the chemisorbed O2 precursor species, whereas one of the channels with a larger activation energy is suggested to induce the additional bend in S0(T) near Ttr at higher O2 pressures.