Cluster computations, using density functional theory, were performed in order to clarify the diffusion mechanism of an O atom which was adsorbed on a Si surface. The activation energy which was required for O diffusion into the Si substrate was estimated to be equal to 1.6eV. This was relatively small when compared to the value for O diffusion within a Si crystal. The presence of a surface dangling bond was responsible for the lowering of the activation energy, by assisting the generation of an intermediate which was involved in the rearrangement of the Si-O connections. Adsorption of another O atom on the Si surface appeared to enhance further the inward O diffusion.

Inward Diffusion of Oxygen on a Silicon Surface T.Hoshino, Y.Nishioka: Physical Review Letters, 2000, 84[20], 4633-6