Microstructure development and morphological transition during deposition of immiscible alloy films

Complex three-dimensional microstructural patterns arise during deposition of immiscible alloys and their morphologies depend sensitively on alloy composition, deposition rates and substrate temperatures. Using phase field simulations, we construct a microstructure morphology map in a multi-dimensional space of material properties and processing parameters. We consider simultaneous effects from temperature-dependent surface and bulk diffusivities and thermodynamic driving force for phase separation, temperature- and composition-dependent interphase boundary and surface energies, as well as alloy composition, substrate temperature and deposition rate. The microstructural patterns and morphological transition sequences in as-deposited films revealed by the microstructure map are validated using experimental data from sputtered Cu-Mo alloy films as well as from other systems. Such a microstructural map can guide synthesis of three-dimensional compositionally modulated nanostructures via self-organization during deposition of immiscible alloy films.