Misfit-Dislocation-Mediated Heteroepitaxial Island Diffusion

TL;DR

This paper uncovers a dislocation-mediated diffusion mechanism for copper islands on silver surfaces, showing size-dependent barriers that challenge traditional models and suggest enhanced mass transport during coarsening.

Contribution

It introduces a novel dislocation-mediated diffusion mechanism for heteroepitaxial islands and provides experimental and simulation evidence for size-dependent diffusion barriers.

Findings

Dislocation-mediated diffusion observed in Cu on Ag(111).

Diffusion barriers show non-monotonic size dependence.

Enhanced mass transport during coarsening due to size effects.

Abstract

Scanning tunneling microscopy combined with molecular dynamics simulations reveal a dislocation-mediated island diffusion mechanism for Cu on Ag(111), a highly mismatched system. Cluster motion is tracked with atomic precision at multiple temperatures and diffusion barriers and prefactors are determined from direct measurements of hop rates. The non-monotonic size dependence of the diffusion barrier is in good agreement with simulations and can lead to enhanced mass transport upon coarsening, in surprising contrast to the traditional island diffusion models where diffusivity reduces with cluster size.