Prefactor and Step Edge Barrier Determination for Initerlayer Diffusion in Homoepitaxial Systems: Ag/Ag(111)

Abstract

Interlayer diffusion is controlled by the probability that an atom will hop from a higher to a lower level. This probability depends on the additional step edge barrier ΔEs which an atom experiences at a step because of the lower coordination as it moves over the barrier, and possibly on the different prefactors νs, νt for an atom at the step versus one at a terrace position. It is important to develop experimental methods that separate out the two contributions. We have reanalyzed the STM-based method,1 which measures the fraction of islands with second layer occupation at different deposition temperatures, to show how the two contributions can be identified. In addition, we have developed a diffraction-based method that measures the step density of nucleated islands as they compete for atom capture with the steps at the perimeter of the terraces. RHEED experiments on Ag/Ag(111) result in ΔEs=0.15±0.03 eV and νs/νt=2.3×102±0.2, in good agreement with the results, ΔEs=0.13±0.03 eV and νs/νt=103±0.3, deduced from the data of Ref. 1.