DIAMOND-LIKE CARBON-FILMS DEPOSITED IN A DUAL MICROWAVE RADIOFREQUENCY PLASMA

Diamond-like carbon (DLC) films were deposited from CH4 gas in a dual microwave-radio-frequency (MW-RF) plasma consisting of a microwave discharge with RF power applied to the substrate. We report the effect of the negative d.c. substrate bias voltage on the deposition rate, ion flux and film structure. Substantially higher fluxes were measured in the MW-RF mode than in the "pure" RF mode owing to a higher rate of fragmentation and ionization of the CH4 molecules in the gas phase, as also indicated by optical emission spectroscopy. It has been found by Fourier transform IR spectroscopy that the DLC films deposited in the MW-RF discharge exhibit more sp3 character than the deposits from a "pure" RF plasma. It is shown that DLC films prepared at lower ion energy but higher ion flux in the dual-frequency mode exhibit superior characteristics.