Investigations of the role of the discharge current density in diamond synthesis during filament-enhanced plasma-assisted CVD

The effect of the discharge current density has been studied in order to ob tain fundamental information about the growth of diamond films by a hot-fil ament-assisted chemical vapour deposition method with positive substrate bi as. It is found that the application of a positive bias to the substrate im proves the deposition rate and maintains control of the film's quality. Opt ical emission spectroscopy and mass spectroscopy have been employed to inve stigate in situ the effect of the discharge current density on a gas-phase environment. The increase in discharge current density significantly leads to an enhancement of the conversion of methane to carbon-containing species such as C2H2, CH, CH+ and C-2. in addition, the density of H atoms also in creases with increasing discharge current density. The accelerated electron s are likely to play an important role in these effects. These results sugg est that the influence of the discharge current density on diamond growth i s primarily due to a change in the gas composition.