Growth of high quality spherical diamond film by DC plasma jet CVD

Spherical diamond film was deposited on molybdenum substrate by DC-plasma jet CVD. Scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, and X-ray diffraction (XRD) were used to observed morphology, purities and orientation evolution of spherical diamond film, respectively. The results show that grain size is compact, clear, uniform, continuous and no remarkable bigger grain. When nucleation begins, grain grows with random orientation; after nucleation, grain grows with certain orientation. Characteristic diamond (111), (220), (311) peaks were clearly observed and no graphite peak was detected, and (111) facets were dominant, which indicated diamond film was an obviously polycrystalline texture. At 1332.0 cm(-1) with FWHM, there is a the typical diamond Raman spectra characteristic peaks, and polycrystalline graphite and amorphous graphite were not observed; thus, high quality spherical diamond films were prepared. Upon increasing methane concentration and temperature, grain size also increases, and diamond film has more local clusters and vacancy defects; there are more polycrystalline graphite and amorphous graphite, and diamond film quality was worse. Thus, for preparing high quality diamond film, it is necessary to optimize some parameters, such as methane concentration and substrate temperature.