A Molecular Beam Study of the Trapping and Desorption of Oxygen from Si(100) Surfaces

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Abstract
The trapping and desorption kinetics of oxygen on, Si(100) surfaces have been studied by a pulsed molecular beam method. The trapping process in a physisorbed well is a dominant process for the incident energy below 0.09 eV. Above 0.3 eV, the trapping probability decreases with increasing incident energy or with increasing surface temperature. The trapping process is explained by a simple hard cube model. The desorption yield increases with surface temperature for a low coverage surface. Taking the decrease in the sticking probability with surface temperature into account [M. P. D'Evelyn, et al.: Surf. Sci. 186 (1987) 75], this is direct evidence for the physisorbed oxygen-mediated dissociative adsorption which is considered to be an initial stage of the oxidation of Si. The activation energy for dissociative adsorption of physisorbed oxygen increases with oxygen coverage.