SELF-DIFFUSION AND DYNAMIC BEHAVIOR OF ATOMS AT STEP EDGES OF IRIDIUMSURFACES

Steps are an integral part of a surface. Many surface phenomena are to a very large extent affected or determined by the existence of lattic e steps. We report a study of the dynamic behavior of atoms at step ed ges and on stepped surfaces of iridium. Diffusion of edge atoms along steps of different atomic structures, detachment or dissociation of st ep-edge atoms, descending and ascending motions of atoms at step edges , the upward movement of in-layer atoms, and the stable structure of n anometer-size islands have been investigated, and the activation barri er heights of various atomic processes at lattice steps have been deri ved. We have also derived parameters of adatom diffusion on the terrac e of the Ir(113) and (331) surfaces to compare with those of ledge-ato m diffusion along step edges of the Ir(111). Possible implications of the behavior of atoms at lattice steps in thin-film epitaxy are also d iscussed.