Phase-field models for simulating physical vapor deposition and grain evolution of isotropic single-phase polycrystalline thin films

Abstract

2016-11-03T14:11:40

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

“…It is important to note several limitations, which have been assumed in this first treatment for simplicity. First, real materials have grain orientations and grain boundaries associated with the phases present, which are neglected in this work but were the focus for PVD simulations of a single-phase material in Stewart and Spearot [19,20]. Furthermore, these grains may have preferred growth directions or anisotropies that influence PVD growth dynamics, which are also neglected.…”

“…With this, the local solid density has a similar interpretation as the field variables in the multiphase model, which also define the volume fraction of each phase at a given location [19].…”

“…To capture arbitrary surface morphology formation, surface tension and diffusion, and nonlocal shadowing effects during PVD, this work utilizes the interfacial growth model of Keblinski et al [18], which was also used in [19,20] (1) is formally the Cahn-Hilliard dynamics where the variational derivative of the double well free energy functional for this model has been calculated, providing an energy barrier between the vacuum and solid phases. This term allows the formation of arbitrary surface morphologies and accounts for both surface and bulk diffusion during thin film growth, where is the surface diffusion coefficient.…”

“…The non-dimensional parameters in Eqs. (1) and (2) are chosen to produce columnar and porous features during purely vertical PVD simulations as described in [18,19,20]; these parameters are summarized in Table 1. The non-dimensional spatial discretization is taken to be as in Keblinski et al [18] while the non-dimensional temporal discretization is taken to be .…”

“…Recently, Stewart and Spearot [19,20] developed two phase-field models for simulating PVD of a single-phase polycrystalline material. In that work, a traditional single free energy functional approach for describing the energetics of a PVD thin film system was compared to a coupled approach that treated the PVD growth process as being separate from the subsurface grain evolution process (i.e., different free energy expressions for each process).…”