Nanocrystalline diamond/β-SiC composite interlayers for the deposition of continuous diamond films on W and Mo substrate materials

Nanocrystalline diamond/β-SiC composite film system has been realized as an interlayer for the deposition of continuous and adherent diamond thin films on W and Mo substrate materials by microwave plasma chemical vapor deposition (MWCVD) technique in a single process step using a gas mixture of H2, CH4, and tetramethylsilane [Si(CH3)4, TMS]. Continuous and high quality diamond film growth on the interlayers was clearly evident. Scanning electron microscopy, X-ray diffraction and micro Raman scattering studies have been carried out to study the surface morphology and the crystal structure of the deposited films. The composite films consist of mainly two phases that of diamond and β-SiC. Content of β-SiC in these films can be varied by varying the concentration of TMS in the gas phase reaction. Diamond top layers on different composite interlayers are found to be possessing low residual stress values and simple Brinell indentation tests showed an improved adherence of these top layers in comparison to those deposited directly on the pre-treated substrates. Even the homogeneous composite (i.e., without the diamond top layers) as well as the gradient composite interlayers when considered as separate thin film systems, showed a very good adherence.