Minimum energy paths for dislocation nucleation in strained epitaxial layers

TL;DR

This paper investigates the energy barriers and transition paths for dislocation nucleation in strained epitaxial layers using atomistic simulations, revealing a tensile-compressive asymmetry in the process.

Contribution

It introduces a numerical approach combining repulsive potential minimization and Nudged Elastic Band method to identify minimum energy paths for dislocation nucleation.

Findings

Identifies the minimum energy barrier for dislocation nucleation.

Discovers a strong tensile-compressive asymmetry in transition paths.

Provides insights into stress relaxation mechanisms in epitaxial layers.

Abstract

We study numerically the minimum energy path and energy barriers for dislocation nucleation in a two-dimensional atomistic model of strained epitaxial layers on a substrate with lattice misfit. Stress relaxation processes from coherent to incoherent states for different transition paths are determined using saddle point search based on a combination of repulsive potential minimization and the Nudged Elastic Band method. The minimum energy barrier leading to a final state with a single misfit dislocation nucleation is determined. A strong tensile-compressive asymmetry is observed. This asymmetry can be understood in terms of the qualitatively different transition paths for the tensile and compressive strains.