Self-diffusion and dynamic behavior of atoms at step edges of iridium surfaces

Steps are an integral part of a surface. Many surface phenomena are to a very large extent affected or determined by the existence of lattice steps. We report a study of the dynamic behavior of atoms at step edges and on stepped surfaces of iridium. Diffusion of edge atoms along steps of different atomic structures, detachment or dissociation of step-edge atoms, descending and ascending motions of atoms at step edges, the upward movement of in-layer atoms, and the stable structure of nanometer-size islands have been investigated, and the activation barrier heights of various atomic processes at lattice steps have been derived. We have also derived parameters of adatom diffusion on the terrace of the Ir(113) and (331) surfaces to compare with those of ledge-atom diffusion along step edges of the Ir(111). Possible implications of the behavior of atoms at lattice steps in thin-film epitaxy are also discussed.