Studies Of Synthesizing Nano-crystalline Diamond Films

Nano-crystalline diamond (NCD) and Ultranano-crystalline diamond (UNCD), compared to the micron diamond films, have great application prospect in high-power and high-frequency semiconductors due to its excellent properties, such as high thermal conductivity, high elastic modulus, high dielectric breakdown field strength and high carrier mobility. At present, the most important problem in the field of NCD/UNCD film semiconductor applications need to be solved:how to get a large area, high flatness NCD/UNCD work layer.If this problem can be solved, the industrialization of NCD/UNCD semiconductor will be just around the corner.In this work, the growth and doping technique of NCD films was studied by Microwave Plasma Chemical Vapor Deposition (MPCVD) system, based on this experiment and continue to use this device research the process parameters of UNCD and trying to provide a good industrial application of nano-crystalline and ultranano-crystalline diamond films theories.The new multimode microwave frequency of MPCVD devices for NCD deposition is2.45GHz. and the maximum output power is10kW. TMoi and TM02were two microwave modes that mainly be used in the experiment. The superposition of two microwave modes can form a diameter of about150mm ball of plasma above the water-cooled substrate, which can realize the objective of the deposition of large area diamond films. The growth and doping technique of NCD films was prepared on mirror polished single-crystalline silicon substrate, which grinded by nano-diamond powder before the deposition of NCD to improve the nucleation rate. By analyzing the deposition temperature, microwave power, reaction pressure, carbon source concentration and nucleation density on the influence of the nano-crystalline diamond thin film deposition.Ultranano-crystalline diamond films on silicon substrate was carried out on the new multimode microwave frequency of MPCVD devices.Respectively using CH4/H2/N2and CH4/H2/Ar gas system and with the help of N2and Ar on further refine the diamond grain size to get ultranano-crystalline diamond films.Using SEM, XRD, Raman spectrum analysis of the diamond films which were synthesised by the two different gas system.In CH4/H2/N2gas system failed to preparation of ultranano-crystalline diamond,the smallest grain size of diamond film synthesised by this system was21.6nm.In CH4/H2/Ar gas system, We successfully synthesised ultranano-crystalline diamond film and the the minimum grain size to5.4nm.In this thesis, the research provided good experimental guidance to prepare a large area, high smoothness of NCD and UNCD thin film and good experimental basis for the NCD and UNCD film semiconductor applications.