Deposition of c-BN on silicon substrates coated with diamond thin films

By controlling the pretreatment processes and deposition parameters on silicon substrates, diamond thin films with different surface roughness and sp2/sp3 ratio were used as an interlayer for subsequent c-BN (cubic boron nitride) thin film deposition studies. The diamond interlayers were prepared by microwave plasma chemical vapor deposition (CVD), while the c-BN top layers were prepared by unbalanced magnetron sputtering physical vapor deposition. The substrate curvature changes before and after the c-BN deposition were measured to better understand the relationship between film stress and adhesion to the diamond. In the range of our experimental parameters, results showed that a rougher surface and higher ratio of sp2/sp3 in the diamond layer improves the adhesive strength of the c-BN layer. An optimized layer structure of Si/diamond/BN is established. Grading of the diamond layer is expected to be helpful for adhesion enhancement of c-BN thin films on diamond interlayers.