EFFECT OF SILICON DOPING IN CVD DIAMOND FILMS FROM MICROCRYSTALLINE TO NANOCRYSTALLINE ON WC-Co SUBSTRATES

Si-doped diamond films with various Si concentrations are deposited on WC-Co substrates using HFCVD method, with the mixture of acetone, tetraethoxysilane (TEOS) and hydrogen as the reactant source. A variety of characterizations, including FE-SEM, AFM, Raman, XRD, surface profilometer and Rockwell indentation, are conducted to systematically investigate the influence of Si incorporation on diamond films. As the Si/C ratio from 0% to 5%, the grain size of as-deposited films decreases from 4 μm to about 50 nm, and the surface roughness reduces from Ra ~ 290 nm to Ra ~ 180 nm. Besides, the intensity ratio of I(111)/I(220) varies from 0.57 to 0, indicating the 〈110〉 preferred orientation of the nanocrystalline structure in the 5% doped diamond films. The silicon doping is beneficial for the formation of non-diamond carbide phases in the films, according to the Raman spectra. Moreover, the film adhesion is also improved with the increase of Si/C ratio.