Low temperature deposition of diamond using chloromethane in a hot-filament chemical vapor deposition reactor

Chloromethanes (CH₂Cl₂, CHCl₃ and CCl₄) were used as carbon sources to grow diamond at low temperature (from 380 °C to 700 °C). In comparison with methane, which is inefficient at growing diamond below 600 °C, chloromethane was quite suitable for the growth of diamond films at low temperature. Diamond growth was possible even at 380 °C, which was the lowest temperature possible in the system utilized here, using CCl₄ reactant. Scanning electron micrographs, X-ray diffraction patterns and Raman spectra confirmed the presence of diamond crystallites. However, the growth rate at 380 °C was only 0.05 μm h^-1. Improved growth rates were achieved with hydrogen passing through the hot-filament and carbon source gas bypassing the filament (bypass configuration). The growth rate of diamond was indeed enhanced very significantly using chloromethane in the bypass configuration. However, problems such as non-uniform growth and a narrow range of possible growth parameters arose using the bypass configuration. In contrast, the growth rate was not enhanced by using methane in the bypass configuration. The advantages of chloromethane are demonstrated. Possible reasons for such advantages are also discussed.