The origin and properties of the wetting layer and early evolution of epitaxially strained thin films

Abstract

We showed that a wetting layer in epitaxially strained thin films which decreases with increasing lattice mismatch strain arises due to the variation of nonlinear elastic free energy with film thickness. We calculated how and at what thickness a flat film becomes unstable to perturbations of varying size for films with both isotropic and anisotropic surface tension. We showed 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 also studied the early evolution of epitaxially strained films. We found that film growth is dependent on the mode of material deposition. The growth of a perturbation in a flat film is found to obey robust scaling relations. These scaling relations differ for isotropic and anisotropic surface tension.