Elasticity effects on the stability of growing films

TL;DR

This paper investigates how elasticity influences the stability and pattern formation in growing thin films, revealing that elastic coupling destabilizes uniform layers and promotes nanostructure formation, including square patterns.

Contribution

It introduces a coupled model of coverage dynamics and film elasticity, showing elasticity's destabilizing role and its impact on nanostructure patterns during film growth.

Findings

Elastic coupling destabilizes uniform film layers.

Elastic effects promote square nanostructure patterns.

Coverage inhomogeneities generate internal stresses that influence pattern selection.

Abstract

It is shown how the combination of atomic deposition and nonlinear diffusion may lead, below a critical temperature, to the growth of nonuniform layers on a substrate. The dynamics of such a system is of the Cahn-Hilliard type, supplemented by reaction terms representing adsorption-desorption processes. The instability of uniform layers leads to the formation of nanostructures which correspond to regular spatial variations of substrate coverage. Since coverage inhomogeneities generate internal stresses, the coupling between coverage evolution and film elasticity fields is also considered, for film thickness below the critical thickness for misfit dislocation nucleation. It is shown that this coupling is destabilizing and favors nanostructure formation. It also favors square planforms which could compete, and even dominate over the haxagonal or stripe nanostructures induced by coverage dynamics alone