Jump processes in surface diffusion

The traditional view of the surface diffusion of metal atoms on metal surfaces was that atoms carry on a random walk between nearest-neighbor surface sites. Through field ion microscopic observations and molecular dynamics simulations this picture has been changed completely. Diffusion by an adatom exchanging with an atom of the substrate has been identified on fcc(110), and subsequently also on fcc(100) planes. At elevated temperatures, multiple events have been found by simulations in which an atom enters the lattice, and a lattice atom at some distance from the entry point pops out. Much at the same time the contribution of long jumps, spanning more than a nearest-neighbour distance, has been examined; their rates have been measured, and such transitions have been found to contribute significantly, at least on tungsten surfaces. As higher diffusion temperatures become accessible, additional jump processes can be expected to be revealed.