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

On the Vacancy Formation and Diffusion on the Si(111)7x7 Surfaces under Exposures of Low Oxygen Pressure Studied by in situ Reflection Electron Microscopy. N.Shimizu, Y.Tanishiro, K.Takayanagi, K.Yagi: Surface Science, 1987, 191[1-2], 28-44