A study of diamond synthesis on glassy carbon by the hot filament chemical vapour deposition technique

The hot filament chemical vapour deposition technique was utilized in producing deposits of diamond particles from mixtures of methane and hydrogen onto glassy carbon substrates, in the temperature range 500-760 °C. The deposits and the substrate surfaces were characterized by scanning electron microscopy and Raman spectroscopy. We found that the substrate surfaces were damaged by atomic hydrogen etching, in a more severe way at lower temperatures. The morphological changes suffered by the surfaces during the synthesis process were correlated with the peculiar features shown by the diamond deposits, which tend to arrange in bridge-like clusters of grains. The results of two-step deposition experiments performed at 760 °C are also reported. Removal of the scarcely adherent crystallites deposited during the second process run enabled us to analyse the surface left beneath them using Auger electron spectroscopy, and to determine that nucleation of the second-layer particles occurred on a graphitic layer.