The diffusion coefficients were deduced from a coverage profile analysis of photo-emission electron microscopic images. The diffusion coefficients of O on a (110) surface were obtained for temperatures ranging from 606 to 668K. The O exhibited an anisotropy; with diffusion occurring essentially only parallel to the [1¯10] direction. It also exhibited a marked coverage dependence. At an O coverage of less than 0.2 of a monolayer, the diffusion coefficient was larger (by an order of magnitude), than that at high coverages. The O required an activation energy of 30kcal/mol at low coverages and of 40kcal/mol at high coverages.

A.Von Oertzen, H.H.Rotermund, S.Nettesheim: Surface Science, 1994, 311[3], 322-30