Continuum field model of defect-induced heterogeneities in a strained thin layer

TL;DR

This paper develops a continuum phase-field model to study how external stresses induce defect heterogeneities in strained thin layers, explaining experimental observations of localized defect regions and enhanced fracture toughness.

Contribution

It introduces a coupled defect concentration and displacement field model to predict defect nucleation under external stresses in thin layers.

Findings

External stresses cause nucleation of defect-rich regions in thin layers.

The model explains heterogeneity formation in cobalt disilicide films.

It accounts for improved fracture toughness in zirconia ceramics.

Abstract

We investigate the effect of external stresses on structural and mechanical properties of a strained damaged thin layer by developing a continuum phase-field mesoscale model based on the introduction of an order parameter field, the defect concentration, coupled with a displacement field. We find that even in the case of an initially uniform distribution of point defects external stresses drive the nucleation of local regions with higher concentration of vacancies or self-interstitials than their average value over the film. The effect can explain our experimental findings relating generation of highly heterogeneous regions in cobalt disilicide film fabricated in self-aligned processing on a silicon surface as well as improvement of fracture toughness in a tetragonal zirconia ceramics with oxygen vacancies.