Preferential Diffusion of Vacancies Perpendicular to the Dimers on Si(001)2×1 Surfaces Studied by UHV REM

Abstract

This paper describes anisotropic diffusion of vacancies on Si(001)2×1 surfaces studied by reflection electron microscopy. Vacancies were introduced uniformly on surface terraces of rectangular 2×1 and 1×2 domains of similar size by exposure to oxygen at 10^-8Torr at 700°C. The longer sides of the 2×1 and 1×2 domains were perpendicular and parallel to the dimer direction, respectively. It was observed that hollows were nucleated by coalescence of the vacancies preferably in the 2×1 domains. This was due to anisotropy of vacancy diffusion which caused different vacancy concentrations in the two domains. This fact indicates that easy diffusion of the vacancies is perpendicular to the dimer direction.