, CHANDRABHAS NARAYANA

Abstract. Polycrystalline diamond coatings are grown on Si (100) substrate by hot filament CVD technique. We investigate here the effect of substrate roughening on the substrate temperature and methane concentra-tion required to maintain high quality, high growth rate and faceted morphology of the diamond coatings. It has been shown that as we increase the substrate roughness from 0⋅05 μm to 0⋅91 μm (centre line average or CLA) there is enhancement in deposited film quality (Raman peak intensity ratio of sp 3 to non-sp 3 content increases from 1⋅65 to 7⋅13) and the substrate temperature can be brought down to 640°C without any addi-tional substrate heating. The coatings grown at adverse conditions for sp 3 deposition has cauliflower morpho-logy with nanocrystalline grains and coatings grown under favourable sp 3 condition gives clear faceted grains