Mechanical and electrical properties of diamond-like carbon films deposited by plasma source ion implantation

Abstract

Diamond-like carbon (DLC) films were prepared by a plasma source ion implantation method with superposed negative pulse and negative DC voltage. Acetylene gas was used as working gas for plasma formation. 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 −4.8kV and the pulse voltage was changed from −18 to −13.2kV. The films were annealed in the range of 200–450°C for 1h. The surface morphology of the films and the film thickness were observed by atomic force microscopy and scanning electron microscopy. The film structure was characterized by Raman spectroscopy. The hardness of DLC films was evaluated by an indentation method. Measurement of the electrical resistivity was performed using a four-point probe station. Furthermore, a ball-on-disc test with 2N load was employed to obtain information about the friction properties and sliding wear resistance of the films.The surface of the DLC films was very smooth and featureless. The deposition rate was changed with the DC voltage and pulse conditions. Integrated intensity ratios ID/IG of Raman spectroscopy and electrical resistivity of the DLC films changed with DC voltage. The electrical resistivity decreased with increasing ID/IG ratio. The ID/IG ratio was increased and the electrical resistivity was decreased with annealing temperature owing to graphitization. Very low friction coefficients around 0.05 were obtained for as-deposited films.