Optimising diamond nucleation via combined pre-treatments

Diamond thin film deposition on copper substrates has been carried out using hot filament chemical vapour deposition (HFCVD). Surface pre-treatment methods such as substrate polishing and biasing have been employed in order to maximise diamond grain density. We show that by combining substrate polishing and biasing there is an enhancement in the diamond grain density in comparison 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 Raman spectrum. The graphite phase is essentially acting as the precursor for subsequent diamond deposition. It was found that this material, which consists of a network of amorphous carbon and microcrystalline graphite, was readily etched when exposed to the hydrogen plasma. Subsequent diamond deposition under standard CVD conditions completely covers the amorphous carbon layer with diamond until a uniform film is deposited. Interestingly, after diamond deposition for 5 h Raman spectra no longer displays the D- and G-bands of microcrystalline graphite. In this paper, the characteristics of the glow discharge which are expected to have a significant effect on diamond nucleation have also been studied. (C) 2000 Elsevier Science B.V. All rights reserved.