Diamond growth on WC-Co substrates by hot filament chemical vapor deposition: Effect of filament–substrate separation

Polycrystalline diamond films have been grown by hot filament (HF) chemical vapor deposition on WC-Co bar substrates using different CH4/H2 source gas mixing ratios and two different total gas pressures. Each substrate was mounted so as to span a range of HF-substrate separations, df, (and thus substrate temperatures) and therefore samples a spread of incident gas phase chemistry and compositions. Spatially resolved scanning electron microscopy and Raman analysis of the deposited material provides a detailed picture of the evolution of film morphology, growth rate, sp3/sp2 content and stress with df in each deposited sample, and of how these properties vary with process conditions. The experimental study is complemented by two-dimensional model calculations of the HF-activated gas phase chemistry and composition, which succeeds in reproducing the measured growth rates well.

Research Highlights
► Polycrystalline diamond films were grown on WC-Co bar substrates by HF-CVD.
► Each substrate was mounted to span a range of HF-substrate distances (df).
► We provided the df dependence of the film morphology, growth rate, sp3/sp2 content and stress for each sample.
► We provided new insights into the carriers of the various features evident in Raman spectra of diamond films.
► The experimental study is complemented by 2D model calculations of the HF-activated gas phase chemistry.