Growth controlling of diamond and β-SiC microcrystals in the diamond/β-SiC composite films

Diamond/β-SiC composite films are prepared with varied gas phase compositions at increased microwave power density in the microwave plasma chemical vapor deposition process. Scanning electron microscope (SEM), X-ray diffraction (XRD) and micro-Raman measurements are carried out to characterize the change of phase composition, morphology and orientation of the composite films. A reduction in the growth rates of the diamond and β-SiC microcrystals is observed which results in the higher density of defects in the diamond crystals and lower growth rates of the composite films in comparison with those of the pure diamond film. XRD measurements show that the addition of a low CH4 flow rate can lead to the (100) oriented growth of the β-SiC phase, while an increase in the CH4 flow rate results in a randomly oriented β-SiC phase in the composite film. Based on the overall experimental observation, the growth mechanism of the composite films at increased microwave power density is proposed. The continuous formation of defects on the diamond and β-SiC crystals (induced by the bonding of Si and excess carbon containing species onto diamond and β-SiC crystals, respectively) and their subsequent etching by atomic hydrogen are important in affecting the growth rates and orientation of the composite films.