Preparation of Nano-Crystalline Diamond Films on Poly-Crystalline Diamond Thick Films by Microwave Plasma Enhanced Chemical Vapor Deposition

Nano-crystalline diamond （NCD） films were prepared on poly-crystalline diamond（PCD） thick films by the microwave plasma enhanced chemical vapor deposition （MPCVD）method. Free standing PCD thick film （50 mm in diameter） with a thickness of 413 μm wasdeposited in CH;/H;plasma. It was then abraded for 2 hours and finally cut into pieces in asize of 10×10 mm;by pulse laser. NCD films were deposited on the thick film substrates byintroducing a micro-crystalline diamond （MCD） interlayer. Results showed that a higher carbonconcentration （5%） and a lower substrate temperature （650℃） were feasible to obtain a highlysmooth interlayer, and the appropriate addition of oxygen （2%） into the gas mixture was conduciveto obtaining a smooth nano-crystalline diamond film with a tiny grain size.