Diamond deposition by hot filament and microwave CVD - Influence of deposition parameters on phase purity, surface roughness and film quality

We report on the deposition of diamond films by two different methods: hot filament and microwave CVD, giving emphasis to the influence of process parameters on phase purity and film quality (homogeneity over large areas, surface roughness). Maximum deposition areas are in the range of 50 x 50 mm. A specially designed filament support prevents the tungsten filament from bending, ensuring a constant distance to the substrate. Additionally, this support minimizes the effect of thermal stress when the filament is turned on or off, so that many cycles of operation are possible. The results of our deposition experiments suggest that the filament temperature is more important for film quality than substrate temperature. For the microwave-deposited diamond, the influence of the film stress on the peak shift was investigated with Raman spectroscopy. These shifts are comparable with data on single crystal diamond under pressure.