Stress release mechanisms for Cu on Pd(111) in the submonolayer and monolayer regimes

TL;DR

This study investigates how copper layers relax strain on palladium surfaces during initial growth, revealing the formation of stacking domains and dislocations, which differ from perfect epitaxial layers.

Contribution

It introduces computational methods to analyze strain relaxation mechanisms in Cu/Pd(111), highlighting the formation of stacking domains and dislocations at low coverages.

Findings

Cu forms fcc and hcp stacking domains

Layer growth mode is layer-by-layer

Partial misfit dislocations are present

Abstract

We study the strain relaxation mechanisms of Cu on Pd(111) up to the monolayer regime using two different computational methodologies, basin-hopping global optimization and energy minimization with a repulsive bias potential. Our numerical results are consistent with experimentally observed layer-by-layer growth mode. However, we find that the structure of the Cu layer is not fully pseudomorphic even at low coverages. Instead, the Cu adsorbates forms fcc and hcp stacking domains, separated by partial misfit dislocations. We also estimate the minimum energy path and energy barriers for transitions from the ideal epitaxial state to the fcc-hcp domain pattern.