Hydrogen-free DLC films fabricated using superimposed HiPIMS-DCMS deposition system: Bias voltage effects

Diamond-like carbon (DLC) films were grown using a superimposed high-power pulse magnetron sputtering and direct current magnetron sputtering (HiPIMS-DCMS) deposition system at various bias voltages from 0 to −350 V. The microstructure, mechanical and tribological properties of the films were studied in relation to bias voltage. The results suggested that the deposition rate of DLC films decreased gradually with the enhancement of bias voltages. The surface roughness of DLC films decreased from 2.81 nm to 0.54 nm. The values of ID/IG of DLC films decreased first and increased later with the enhancement of bias voltages, and the value of ID/IG was the minimum at −150 V. Therefore, the highest sp3 CC fraction of DLC film was obtained when deposited at −150 V. Moreover, the hardness and internal stress of DLC films also show the law of increasing first and decreasing later. DLC film obtained the maximum hardness and highest internal stress of 32.0 GPa and − 2.08 GPa at −150 V. Finally, the friction test suggested that the films had excellent tribological performance. In particular, the film deposited at −150 V had excellent tribological properties, including low friction coefficient (0.095) and low wear rate (1.36 × 10−7 mm3/N·m). [Display omitted] •DLC films were fabricated using a novel superimposed HiPIMS-DCMS deposition system.•The microstructure, mechanical and tribological properties of DLC films were investigated.•Surface morphology of DLC films evolved from rough to smooth with the increase of bias voltage from 0 V to −350 V.•Appropriate bias voltage had a positive effect on the increase of sp3 CC bonds in DLC films.•DLC film had ultra-high hardness of 32.0 GPa and low wear rate of 1.36 × 10−7 mm3/N·m at −150 V.