MICROSTRUCTURE AND CHARACTERIZATION OF DIAMOND FILM GROWN ON VARIOUS SUBSTRATES

High purity diamond films were successfully grown on various substrate materials, including silicon, SiC, fused silica and a number of refractory metals, by low pressure microwave plasma chemical vapour deposition from CH4:H-2 gas mixtures. The morphology and microstructures were studied using scanning electron microscopy and transmission electron microscopy, and characterized by x-ray diffraction. Auger electron spectroscopy, energy electron loss spectroscopy, electron dispersive spectroscopy and Raman spectroscopy. The results indicate that cubo-octahedra are the equilibrium shapes of crystalline diamond. Both {100} and {111} facets were observed in all the substrates studied. SiC, SiO, amorphous carbon and carbides of refractory metals are the dominant interphases in this study. The composition and microstructure of the interphase appear to have significant effects on the adhesion strength, as shown in the diamond/molybdenum and diamond/hafnium systems. Structural defects such as twins were frequently observed inside the diamond grains, while line defects of dislocations were mainly constrained to the grain boundaries. The surface of the substrate was modified using a process that ultrasonically stimulated cavitation-erosion in an aqueous suspension of diamond dust. The diamond crystallites were of a more uniform size that was achieved after the more conventional lapping process (mechanical polishing).