Nanostructural evolution in vapor deposited phase-separating binary alloy films of non-equimolar compositions: Insights from a 3D phase-field approach

Abstract

A rich variety of self-organized nanoscale patterns evolve during physical vapor deposition of phase-separating alloy films. However, our limited understanding of the fundamental mechanisms of morphological evolution during the vapor deposition of multi-component metallic films is a major hurdle in optimizing their mechanical and functional properties. Diffuse interface approaches, such as the phase-field method, can enable the prediction of nanostructured morphologies in a broad class of immiscible binary alloys by achieving a fundamental understanding of self-assembly mechanisms down to the nanometer scale. Here, we adopt a three-dimensional phase-field approach to numerically investigate the role of alloy compositions, deposition rates, and temperature on the morphological self-assembly of nanostructures in vapor deposited alloy films. We explain the influence of alloy composition and deposition parameters on the evolution of novel film morphologies such as perforated layered and aligned rods. Following an extensive parametric study, we construct morphology maps that help expand our knowledge of the different combinations of processing conditions that generate distinct nanoscaled morphologies. Finally, we expand and elucidate a theory based on the minimization of interfacial energy that underpins the mechanisms of morphological transitions in vapor deposition of immiscible alloy films for an entire composition range.