Diamond/WC bilayer formation mechanism by hot-filament CVD

A method for the growth of Diamond/WC bilayers in a single process is presented with interest for the production of well adhered electrical contacts to diamond surfaces. This process uses a common hot filament chemical vapor deposition (HFCVD) reactor, with W filaments as the source for the deposition of the metallic layer, and H2 and CH4 gasses as the reactive species for the diamond growth. The method begins by vaporizing the filaments in vacuum for a few minutes, followed by the chemical vapor deposition of diamond. The results have shown that by varying the filament vaporization time and temperature it is possible to deposit on the Si substrate tungsten containing coatings of different thicknesses. The process starts by vaporization of naturally oxidized filaments and deposition on the substrate. Afterward, the tungsten oxide carburises to W2C and WC phases. The CVD growth of the diamond layers on these carbide layers is dependent on the CH4/H2 ratios, system pressure and substrate temperature. The seeding of the Si substrates with diamond powder before the CVD process, guarantees that diamond is nucleated inside the metallic carbide layer, anchoring the top nanocrystalline diamond layer.

► Single process growth of diamond/tungsten carbide bilayers.
► Synthesis by hot-filament chemical vapor deposition with methane and hydrogen gasses.
► Influence of the diamond seeding process on the morphology of the bilayer coating.
► WC thickness and CH4 concentration determines the formation of continuous diamond coatings.
► Model of the mechanism responsible for the growth of the WC/diamond film.