Study on the Structure of the Unpaired Electron in Diamond Films and Trials to Reduce the Unpaired Electron

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We studied how does the density of paramagnetic defect in diamond films change, when they are composed of oriented crystal grains. (100)-oriented diamond films having various morphology were deposited on silicon (100) substrates from a mixture of methane, carbon dioxide and hydrogen using bias-assisted microwave CVD method. To obtain highly oriented films, it is necessary to form a checked nano-pattern on the silicon substrate by carburization and bias-enhanced nucleation (BEN). The detail of these processes, however, is not well known. We formed the nano-pattern by adjusting process parameters such as the microwave power, the methane concentration, the pretreatment time, the gas pressure and the bias voltage. Quality of the diamond films grown on the nano-patterns was evaluated, and the following results were obtained.(1) The microwave power, the gas pressure, the treatment time and the bias voltage are important parameters in order to form a clear nano-pattern.(2) To make clear the nano-pattern is necessary for improving the (100) orientation of diamond, but an excessive clearness by prolonged BEN treatment results in deterioration for the orientation.(3) Diamond growth after the pretreatment is better if methane and hydrogen is used without adding carbon dioxide.(4) There are two kinds of center in addition to the H1 center as for paramagnetic defect in the film.(5) There is paramagnetic defect of a density of 10^<18> cm^<-3>, even in the film prepared by optimizing the pattern formation and diamond growth process. This results from the remaining of various stress in the film.(6) A new ESR center is found in the film prepared by adding carbon dioxide.