Self-diffusion on stepped Ir(111) surfaces

Abstract

We investigate diffusion processes for interlayer transport on Ir(111) surfaces in which we consider hopping and exchange mechanisms at perfect step edges as well as at step edges with defects. From molecular dynamics simulations and from explicit calculations of activation barriers and prefactors within transition state theory we find that an Ehrlich-Schw\"obel barrier of 0.5 eV exists for step descent. All in all, we find activation barriers and prefactors to be lower for hopping than for exchange at the respective step edges and present a detailed analysis of where the differences in the prefactors originate. The most favorable paths for step descent are hopping and exchange at the (100) microfacetted step edge with one vacancy, where hopping is most probable at low temperatures, while exchange becomes more favorable at higher temperatures.