Morphological stability and compositional uniformity of alloy thin films

Alloy thin films differ from pure materials in two respects: the alloy components may be prone to phase separation and the lattice parameter of the film is generally a function of the alloy composition. Both of these characteristics affect the compositional uniformity of the film, which has implications for the film's mechanical and opto-electronic properties. To explore these phenomena, we present a linear stability analysis of alloy film growth, which accounts for the stresses generated by both film-substrate misfit and compositional nonuniformities. We find that, when compositional stresses are considered, an instability can be present and that this instability is generic to alloy crystal growth. This instability is due to the deposition process, along with compositionally generated stresses, and occurs even in the absence of a film-substrate misfit. We compare our predictions to other related models and to the experimental literature.