Growth rate improvements in the hot-filament CVD deposition of nanocrystalline diamond

The hot-filament CVD, a less used technique for NCD films growth using Ar/H2/CH4 gas mixtures, is optimized for the coating of silicon nitride ceramics. Parameters such as gas composition (Ar/H2 and CH4/H2 ratios), total gas pressure, total mass flow and substrate and filament temperatures, are studied to assess their effect on NCD growth kinetics as well as on film quality and morphology. The smallest diamond crystallite sizes (8 nm) were recorded for the slowest growth rate of 0.1 μm h− 1. A remarkable result is the very high growth rate of 1.6 μm h− 1 of continuous NCD coatings with 28 nm of crystallite size, obtained in selected deposition conditions.