Characteristics of diamond crystals deposited on quartz substrates by chemical vapor deposition

Individual diamond crystals have been deposited on quartz substrates by the hot-filament-assisted chemical vapor deposition (CVD) method. The crystals were symmetrical cubo-octahedron and colorless, and exhibited a bright center when illuminated under visible light. All crystals were untruncated at the quartz surface and could be scratched off from the quartz easily. It was proposed that the untruncated crystals grew directly on the diamond seeds that remained on the quartz surface after the diamond powder pretreatment. The quartz surface was chemically passive in respect of hydrocarbon chemisorption under the CVD conditions. As a result, no transition interlayer that could truncate the diamond crystals was formed between diamond and the quartz substrate. The phenomenon of the bright center under light illumination was attributed to the combinative effect of optical refraction and reflection at crystal facets and scattering by defects within the crystals.