Preparation and Properties of Diamond-Like Carbon Films from CH4, C2H4, and C2H2 with Plasma Source Ion Implantation

Diamond-like carbon (DLC) films were prepared on silicon wafer substrates by plasma source ion implantation (PSII) with superposed negative pulse. Methane, ethylene and acetylene gases were used as working gases for plasma. A negative DC voltage and a negative pulse voltage were superposed and applied to the substrate holder. The DC voltage was changed in the range from 0 to -4 kV and the pulse voltage was changed from 0 to -18 kV. The surface of DLC films was very smooth. The deposition rate of DLC films increased with increasing in superposed DC bias voltage. ID/IG ratios of Raman spectroscopy were around 1.5 independent on pulse voltage. The hydrogen concentration estimated by an elastic recoil detection (ERD) analysis was in the range from 20 at% to 28 at% depending on the source gas and the deposition condition. The hardness of around 10-20 GPa was derived for the film prepared with high DC and high pulse voltage. The friction coefficient estimated by a ball-on-disc test was around 0.1 for almost films. The residual stress was smaller than 1GPa (compressive) for all films and there was no clear dependence on working gas.