SYNTHESIS OF DIAMOND BETA-SIC COMPOSITE FILMS BY MICROWAVE PLASMA ASSISTED CHEMICAL VAPOR-DEPOSITION

A new kind of microcrystalline composite films consisting of diamond and cubic silicon carbide (beta-SiC) has been synthesized in a microwave plasma assisted chemical vapor deposition process (MWCVD), using a gas mixture of hydrogen, methane, and tetramethylsilane. Single crystalline (111) silicon wafers and polycrystalline tungsten carbide, which were treated with diamond paste before the deposition, were used as substrates. Scanning electron microscopy, electron probe microanalysis, infrared absorption, Raman scattering, and x-ray diffraction analysis were performed to characterize the film quality and the crystallographic structure. The results show that the film structure and the volume fractions of diamond and beta-SiC components depend mainly on the reactive gas concentrations and on the diamond nucleation density. By adjusting the reactive gas concentration, the volume fraction of the components can be varied over the film thickness. In addition, the growth texture of the diamond phases can be influenced by the beta-SiC phase orientation.