A study of diamond synthesis by hot filament chemical vapour deposition on nanocomposite coatings

Deposition of diamond films onto various substrates can result in significant technological advantages in terms of functionality and improved life and performance of components. Diamond is hard, wear resistant, chemically inert and biocompatible and considered as the ideal material for surfaces of cutting tools and biomedical components. However, it is well known that diamond deposition onto technologically important substrates such as Co-cemented carbides and steels is problematic due to carbon interaction with the substrate, low nucleation densities and poor adhesion. Several papers previously published in the relevant literature have reported the application of interlayer materials such as metal nitrides and carbides to provide bonding between diamond and hostile substrates. In this study, we have investigated for the first time the chemical vapour deposition (CVD) of polycrystalline diamond on TiN/SiN x nanocomposite interlayers deposited at relatively low temperatures. The nanocomposite layers were deposited at 70°C or 400°C on silicon substrates by using a dual ion beam deposition system. The results showed that a preliminary seeding pre-treatment with diamond suspension was necessary to achieve large diamond nucleation densities and that diamond nucleation was larger on nanocomposite films than on bare sc-Si submitted to same pre-treatment and CVD process parameters. TiN/SiNx layers synthesized at 70°C or 400°C underwent different nanostructure modifications during diamond CVD. The data also showed that TiN/SiNx films obtained at 400°C are preferable so far as their use as interlayers between hostile substrates and CVD diamond is concerned.