Optimising diamond nucleation via combined pre-treatments

Diamond thin film deposition on copper substrates has been carried out usin g hot filament chemical vapour deposition (HFCVD). Surface pre-treatment me thods such as substrate polishing and biasing have been employed in order t o maximise diamond grain density. We show that by combining substrate polis hing and biasing there is an enhancement in the diamond grain density in co mparison to the results obtained when each pre-treatment method is employed individually. After negatively biasing the substrate for 30 min, broad D- and G-bands of microcrystalline graphite were found to be present in the Ra man spectrum. The graphite phase is essentially acting as the precursor for subsequent diamond deposition. It was found that this material, which cons ists of a network of amorphous carbon and microcrystalline graphite, was re adily etched when exposed to the hydrogen plasma. Subsequent diamond deposi tion under standard CVD conditions completely covers the amorphous carbon l ayer with diamond until a uniform film is deposited. Interestingly, after d iamond deposition for 5 h Raman spectra no longer displays the D- and G-ban ds of microcrystalline graphite. In this paper, the characteristics of the glow discharge which are expected to have a significant effect on diamond n ucleation have also been studied. (C) 2000 Elsevier Science B.V. All rights reserved.