Atomic migration within organized O overlayers on the basal plane of Ru(001) was modelled by using a phenomenological mesoscopic model which accounted for all of the possible atomic jumps within the adsorbate, and several time-scales in the migration kinetics. Experimentally observed diffusion and trapping of isolated O vacancies within a 3O(2 x 2) overlayer, at a coverage of ¾, was explained. Comparisons with experiment were used to deduce the values of the parameters for interactions between an atom adsorbed at an hexagonal close-packed site, and another one temporarily located at some neighboring bridge site. The model was extended to a O(2 x 2) overlayer at a coverage of ¼, and it was shown that a competing diffusion channel existed which broke down the equivalence of the atomic migration behaviors of coverage = ¼ or ¾ overlayers. Simplified effective models were formulated, for both overlayers, which were free of unobservable metastable configurations and unobservable time-scales. Consideration of the ideal O(2 x 1) row-like overlayer, at a coverage of ½, confirmed that occasional jumps of the O atoms to one side of the rows should be observable in scanning tunnelling microscopic images for this overlayer. This contrasted with the situation, for coverage = ¼ and ¾ overlayers, where an excess atom or a vacancy, respectively, was required to initiate observable atomic migration.

Mesoscopic Models of Oxygen Migration on the Ru(001) Surface. M.A.Załuska-Kotur, Z.W.Gortel, R.Teshima: Physical Review B, 2002, 66[16], 165418 (20pp)