Physical vapor deposition of multiphase materials with phase nucleation via a coupled phase-field approach

A coupled phase-field model is presented for simulating physical vapor deposition (PVD) of multi-phase materials, including the effects of phase nucleation. This model is utilized to study the role of initial substrate phase and temperature distributions, which are important experimental deposition parameters, on PVD of a generic allotropic metal with two stable phases. PVD simulations are performed for the deposition of a high temperature phase below its phase transition temperature, and for bicrystal and amorphous substrates with a Gaussian temperature distribution. Several general observations are made from these simulations. During the initial stages of PVD, the substrate phase distribution acts as a template for the growing phases. As the thin film continues to grow, the release of latent heat due to deposition creates a temperature gradient within the film, i.e., regions near the film surface become hotter than near the substrate. Additionally, a substrate with a defined temperature distribution that encompasses temperatures above and below the phase transition temperature, allows for distinguishable regions within the thin film where different phases are stable and continue to grow. Three-dimensional simulations provide additional insight into the role of substrate temperature and phase distribution on the resulting microstructure with different flux rates.