Diffusional phase transformations in self-stressed solid films

Diffusional phase transformations in stressed solid films are simulated by using an analytical solution for the elastic fields together with a numerical solution for the composition evolution. Isotropic and anisotropic (cubic) films are considered, where the film is either free-standing or attached to a substrate. Stresses in the film arise owing to both compositional self-stress and, in the film-substrate case, misfit between the film and substrate. Stresses are found by using analytical elastic solutions we developed for both the two- and three-dimensional cases. Numerical simulations in both two- and three-dimensions are performed using a Cahn-Hilliard model for the composition evolution. Results show that elastic strength, epitaxial misfit, elastic anisotropy, external mechanical loading and film-substrate geometry affect both the kinetics of evolution and the long-time configurations of the evolution. In particular, we observe phenomena such as formation of columnar structures, switching of layers, and phase alignment in preferred directions.