Microstructure Evolution Of Chalcogenide Materials Via Molecular Dynamics

The properties of a material are defined by its granular microstructure which is determined by its grain evolution and the types of grain boundaries present in the structure. For example, the performance of Cadmium Sulfide/Cadmium Telluride (CdS/CdTe) solar cells can be affected by the presence of grain boundaries which makes the study of grain structure evolution a very important part of solar cell performance optimization. Grain boundary mobilities are important properties in material science and engineering as they determine grain structures under given processing and operating conditions. In this thesis, several computational tools were used to analyze the formation and behavior of grains and grain boundaries in polycrystalline CdTe/CdS and bi-crystalline CdTe structures. Recently, the simulated growth of a polycrystalline CdTe/CdS structure via molecular dynamics was reported which very closely mimics the experimental structure of these materials. However, a detailed analysis of the grain boundaries in the simulated CdTe/CdS is lacking. The goal of this thesis is to develop a general methodology to quantitatively analyze the behavior of the grain boundaries in the CdTe/CdS structure. Orientation of the grains within the polycrystalline CdTe/CdS was successfully computed using a combination of computational tools. The determination of the orientation of neighboring grains in a polycrystalline sample is important for computing the type of grain boundaries within the structure. Moreover, the migration of Σ3(111), Σ7(111) and Σ11(311) grain boundaries in CdTe bi-crystals at various temperatures and one driving forces was also computed. The grain boundary migration study is important to calculate the mobility of the grain boundary. Future work will focus on computing the grain boundary types in the polycrystalline sample and studying their dynamic behavior