A theoretical study of diamond growth mechanisms and morphology

The goal of this thesis work was a better understanding of how diamond grows during the chemical vapor deposition (CVD) process. The focus was upon how atomic-level processes affect the observed microstructure of CVD diamond films. The reactions and mechanisms believed to be important in the process of microstructure development were investigated. The methods that were used included ab initio electronic structure calculations and kinetic simulations.; The ab initio methods were used to calculate the energetics for reactions that are necessary for diamond growth. Reactions were studied on the 111 and 100 surfaces of diamond. Clusters of carbon atoms were used as models for these two diamond surfaces. Comparisons were made between reactions that occur within the different structural environments. Differences in the energetics for growth between the 111 and 100 surface were found.; The results from the ab initio calculations were used with results from the literature to develop a diamond growth model that simulated microstructure development. Specifically, the model simulated the dependence of 100 surface growth and 111 surface-site formation upon experimental parameters such as surface temperature and gas-phase composition. This model differed from previous diamond growth simulations due to the inclusion of H-atom and CH₂ migration reactions that were believed to be important for predicting 111 versus 100 film growth. Rate parameters, found either from the literature or determined form ab initio calculations, for 69 possible reactions in the growth process were used. The results from the model showed how the development of microstructure depends upon temperature and gas-phase composition. Migration was shown to be a factor in microstructure development with a set of simulations that prohibited the occurrence of migration reactions. Additional ab initio work was performed in an attempt to improve the rate parameters that were used in the model for surface reactions.