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 was deposited in CH4/H2 plasma. It was then abraded for 2 hours and finally cut into pieces in a size of 10 x 10 mm2 by pulse laser. NCD films were deposited on the thick film substrates by introducing a micro-crystalline diamond (MCD) interlayer. Results showed that a higher carbon concentration (5%) and a lower substrate temperature (6500C) were feasible to obtain a highly smooth interlayer, and the appropriate addition of oxygen (2%) into the gas mixture was conducive to obtaining a smooth nano-crystalline diamond film with a tiny grain size.