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Microstructure Evolution


At the core of manufacturing science is the development of improved processing operations that result on better material properties, reliability, and performance. Fundamentally, this corresponds to first develop a deep understanding to then engineer the microstructural evolution of the fabricated part or device, i.e., the impact of the controlling processing parameters on the time-dependent morphological changes of the individual phases. The focus of this thread of research is on the development of practical analytical and numerical descriptions that will allow to realistically establish design criteria that will accelerate the development of materials and devices of optimal properties. Here, we are currently developing theories, advanced software and visualization techniques that will accelerate such process and will make the analysis of a processing operation an intuitive step on the development of new science and even intellectual property. Simulation techniques such as kinetic Monte Carlo, phase field modeling, and level set methods are adapted, generalized, and integrated to each other in an effort to have a realistic description of the complexity associated to real processing operations.Physical and Chemical Vapor Deposition, Annealing and Sintering, and Electrodeposition are example applications of systems that are being analyzed.

Open Source Symbolic Thermodynamics and Kinetics of Materials

A general purpose open source, Python-based framework, Gibbs, was developed to perform multiphysical equilibrium and kinetic calculations of material properties. The developed architecture allows to prototype symbolic and numerical representations of materials by starting from analytic models, tabulated experimental data, or Thermo-Calc data files. These constructions are based on the addition of arbitrary energy contributions that range from the traditional thermochemical to mechanical and surface tension. Gibbs seamlessly interfaces with FiPy to prototype interdiffusion and microstructural evolution (phase field) models. Through its flexible Graphical User Interface, Gibbs allows rapid deployment of computational thermodynamic applications with intuitive user interfaces, and through the developed viewers, direct visualization and analysis of data can be readily performed for those physical properties that are relevant for the problem at hand. Example applications to chemically homogeneous ferroelectrics and two component (binary) solids are presented.

PVD of Solar Cells

Generalized numerical framework to fabricate solar cells by physical vapor deposition is in the process of being developed. Here, mechanisms of microstructural evolution such as evaporation, condensation, surface tension, surface tension anisotropy occur concurrently during the processing of a thin film and control properties and performance. The current improved model combines the numerical efficiency and elegance of complementary but mutually exclusive numerical techniques to track the natural microstructural evolution that occurs during grain growth and coarsening, phase separation for multicomponent systems for both conserved and non-conserved formulations. We have successfully predicted the developed microstructure during growth and annealing, disorder phase transformations, including an analytical description of the nucleation and growth kinetics of  individual isolated islands and in interaction of multiple neighboring islands (to simulate  coarsening).