Low temperature and large area deposition of nanocrystalline diamond films with distributed antenna array microwave-plasma reactor

• NCD growth was investigated using a new distributed antenna array PECVD system.
• 4-Inch homogeneous NCD films were deposited at substrate temperature of 300–500 °C.
• Growth rate and crystallinity was found to increase with decreasing the pressure.
• Friction coefficient close to that of ta-C coating was obtained.

Diamond films grown at low temperature (< 400 °C) on large area of different substrates can open new applications based on the thermal, electrical and mechanical properties of diamond. In this paper, we present a new distributed antenna array PECVD system, with 16 microwave plasma sources arranged in a 2D matrix, which enables the growth of 4-inch nanocrystalline diamond films (NCD) at substrate temperature in the range of 300–500 °C. The effect of substrate temperature, gas pressure and CH4 concentration in the total gas mixture of H2/CH4/CO2 on the morphology and growth rate of the NCD films is reported. The total gas pressure is found to be a critical deposition parameter for which growth rates and crystalline quality both increasing with decreasing the pressure. Under optimized conditions, the process enables deposition of uniform (~ 10%) and high purity NCD films with very low surface roughness (5–10 nm), grain size of 10 to 20 nm at growth rates close to 40 nm/h. Nanotribology tests result in the friction coefficient of the NCD films close to that obtained for the standard tetrahedral amorphous carbon coatings (ta-C) indicating the suitability of this low-temperature diamond coating for mechanical applications such as bearing or micro-tools.