Rapid decay of vacancy islands at step edges on Ag(111): step orientation dependence

TitleRapid decay of vacancy islands at step edges on Ag(111): step orientation dependence
Publication TypeJournal Article
Year of Publication2010
AuthorsShen MM, Jenks CJ, Evans JW, Thiel PA
Journal TitleJournal of Physics-Condensed Matter
Date Published06/02
ISBN Number0953-8984
Accession NumberISI:000277344500002
Keywordsclusters, complex, diffusion, electronic states, evolution, from-equilibrium nanostructures, growth, interlayer mass-transport, metal-surfaces, quantum confinement

Previous work has established that vacancy islands or pits fill much more quickly when they are in contact with a step edge, such that the common boundary is a double step. The present work focuses on the effect of the orientation of that step, with two possibilities existing for a face centered cubic (111) surface: A- and B-type steps. We find that the following features can depend on the orientation: (1) the shapes of islands while they shrink; (2) whether the island remains attached to the step edge; and (3) the rate of filling. The first two effects can be explained by the different rates of adatom diffusion along the A-and B-steps that define the pit, enhanced by the different filling rates. The third observation-the difference in the filling rate itself-is explained within the context of the concerted exchange mechanism at the double step. This process is facile at all regular sites along B-steps, but only at kink sites along A-steps, which explains the different rates. We also observe that oxygen can greatly accelerate the decay process, although it has no apparent effect on an isolated vacancy island (i.e. an island that is not in contact with a step).

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