Deposition of hydrogenated diamond-like carbon using high power impulse magnetron sputtering*

Diamond-like carbon (DLC) shows high hardness and low friction, and has been applied in tribology field for sliding parts and machining parts. High power impulse magnetron sputtering (HiPIMS) realizes high ionization rate and production of high energy ions, resulting that the DLC film with high hardness more than 20 GPa can be obtained without substrate bias voltage. The deposition rate, however, was lower than DCMS due to high ionization rate and small duty ratio. In this study, hydrogenated DLC film was deposited by reactive HiPIMS using CH4 gas in order to improve deposition rate.

A negative voltage pulse with a voltage of 800 V, a frequency of 400 Hz and a pulse width of 10 μs was applied to the carbon target. The total gas flow rate (Ar+CH4) was 10 sccm, CH4 gas mixture ratio was 20% and the pressure was 0.5 Pa. The negative substrate bias voltage was varied from 100 to 700 V under constant target voltage. ID/IG ratio, which is due to disorder and graphite band, was evaluated by Raman scattering spectroscopy. ID/IG ratio decreased to be 1.0 with increasing bias voltage up to 400 V, and then increased with further increasing bias voltage. Higher substrate bias voltage has been required to improve ID/IG ratio in comparison with the sputtering condition of pure Ar gas.