Phase Field Modeling of the Physical Vapor Deposition of Thin Film Microstructures

Yunbo Wang, Purdue University

Abstract

A theoretical and numerical framework has been developed to predict the microstructures that result from the physical vapor deposition process. The developed model combines the Level Set Method (LSM) to track the solid-gas interface and the Phase Field Method (PFM) to track the natural microstructure evolution in the solid phase for both conserved and non-conserved order parameters during film growth. Physical mechanisms such as evaporation and condensation, the Gibbs-Thomson effect, line-of-sight, and grain impingement and rotation are incorporated to concurrently describe thin film evolution. Application to cadmium telluride recovers and rationalizes a grain size relationship as a function of pressure: df(μm) = 0.027(±0.011) × P(Torr) + 0.90(±0.31) as observed experimentally. An analytical model enables the possibility of macroscopically describing the nucleation and growth process that occurs during deposition in terms of two dimensionless processing parameters by starting from fundamental material properties. The existence of three growth regimes is predicted: Regime α, where nucleation dominates over grain growth, regime β, where grain growth and impingement dominate over nucleation, and regime γ, where nucleation and growth is fully suppressed.

Degree

M.S.M.S.E.

Advisors

Garcia, Purdue University.

Subject Area

Engineering|Materials science

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