In this paper

effect of pressure on deposition temperature for hot filament chemical vapor deposition of diamond thin films was investigated. SEM images show that diamond film of small grain size can be deposited at 500°C by decreasing the pressure from 5.32 kPa to 0.67 kPa. Raman spectra show that the quality of the film deposited at 0.67 kPa and 500°C was as good as that of the film deposited at 5.32 kPa and 700°C. We believe that the deposition of diamond film at low temperature and low pressure is due to the effect of pressure on the concentrations and kinetic energy of the active species near the substrate surface. Compared to the situations with higher pressure

the active species at 0.67 kPa arrive at the substrate surface with higher concentration

which makes it possible for the high-quality diamond films of small grain size can be deposited at very low temperature (500°C).