CRYSTALLOGRAPHIC ORIENTATION AND SURFACE-MORPHOLOGY OF CHEMICAL VAPOR-DEPOSITED AL2O3

Abstract

Deposits of aluminum oxides (A12O3) have been formed by a chemical vapor deposition technique involving the application of gaseous mixtures of A1C13, CO2, and H2 onto TiN-coated cemented carbide substrates. Reaction parameters (deposition temperature, system pressure, and composition of reactant gases) and their effects on the crystalline structure, crystallographic orientation, and surface morphology of the Al2O3 deposit have been studied. Al2O3 crystals maintain a corundum structure throughout the entire range of deposition conditions. Crystals of Al2O3 appear to nucleate in random orientations on the TiN layer, and further growth proceeds with (1014) and (1126) preferred orientations. The effects of reaction parameters on the final surface morphology of the Al2O3 deposit can be described by considering the supersaturations of the reactants and the growth rate. The crystals of the Al2O3 deposit become finer and more uniform as the supersaturation of the reactant controlling the Al2O3 nucleation increases.