Lower filament temperature limit of diamond growth in a hot-filament CVD system

The effect of decreasing filament temperature on growth of diamond films is reported. Well-faceted diamond crystals can be synthesized at a low filament temperature in the range 1500–1700 °C by low-pressure hot-filament chemical vapor deposition with use of a CH4–H2 gas mixture. At a lower filament temperature of 1300 °C, although the morphology of the grains is ball-like in the films deposited, their structure still displays diamond characteristics when assessed by X-ray diffraction and Raman spectroscopy. Under low filament temperature, hot filaments can be used repeatedly many times, have a very long operating life and hold their shape well, which is of special interest for uniform diamond deposition over a large area. The low growth rate and relatively low quality of diamond films due to the low filament temperature can be enhanced to a certain extent by introducing an inert gas.