Wetting layer thickness and early evolution of epitaxially strained thin films

TL;DR

This paper presents a physical model explaining the stability of finite wetting layers in epitaxially strained films, highlighting the roles of elastic free energy, surface tension, and lattice mismatch in film evolution.

Contribution

It introduces a new model that accounts for the stability of wetting layers and the formation of faceted islands in strained thin films.

Findings

Finite wetting layers are stable due to elastic free energy variations.

Anisotropic surface tension leads to metastable enlarged wetting layers.

Lattice mismatch decreases the perturbation amplitude needed for destabilization.

Abstract

We propose a physical model which explains the existence of finite thickness wetting layers in epitaxially strained films. The finite wetting layer is shown to be stable due to the variation of the non-linear elastic free energy with film thickness. We show that anisotropic surface tension gives rise to a metastable enlarged wetting layer. The perturbation amplitude needed to destabilize this wetting layer decreases with increasing lattice mismatch. We observe the development of faceted islands in unstable films.