NUCLEATION AND GROWTH OF DIAMOND ON CEMENTED CARBIDES BY HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION

The experiments were performed on cemented carbide substrates (WC 6%Co). The depositions were carried out using hot-filament chemical vapor deposition and a CH4/H-2 1% gas mixture. The nucleation process was studied on polished and fractured surfaces. We investigated the effects of ultrasonic pretreatment, annealing in molecular hydrogen and deposition temperature on the nucleation rate. The deposition experiments performed on fractured substrates suggest that the main role in enhancing nucleation is played by surface contamination. It was found that when heating at 940-degrees-C in a CH4/H-2 1% activated gas mixture, there is a strong etching effect of cobalt. The growth of diamond films was studied on ground substrates both etched and unetched. The different growth kinetics on etched and unetched substrates in the early stage of deposition are explained.