Strain effect on the instability of island formation in submonolayer heteroepitaxy

A theoretical model is developed to study the strain effect on the instability of island formation in submonolayer heteroepitaxy in both thermodynamic and growth kinetic regimes. By using the linear-stability analysis, the elastic energy change of a circular island is derived. Combined with a rate equation theory, the interplay between growth kinetics and strain effect on the shape instability is analyzed and illustrated with the constructed morphological phase diagrams. Critical island sizes beyond which islands grow unstable are also derived and can be used to estimate the energy parameters. Well-defined scaling properties are also obtained for the shape instability.