Abstract

The formation of vacancies and their diffusion on the Si(111)7×7 surfaces at an initial stage of oxidation are studied by in situ ultrahigh vacuum reflection electron microscopy. In oxygen exposure experiments at low pressures, vacancies are formed on the Si(111)7×7 surfaces due to formation and sublimation of silicon monoxide and they, coalesce into hollows in the central parts of terraces between successive surface atomic steps when the Si surfaces are above 500°C. Distributions of hollows on the surface terraces and their growth kinetics are studied and analyzed. The analysis shows that the activation energy for surface diffusion of the vacancies is ∼1.4 eV and the reaction rate to form two vacancies by an impinging oxygen molecule on the surface is estimated to be ∼0.23 at 630°C.

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