Fabrication of diamond-like carbon films using short-pulse HiPIMS

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Abstract Diamond-like carbon (DLC) films were fabricated by sputtering a graphite target using a short-pulse-operated high-power impulse magnetron sputtering (HiPIMS) technology. The pulse duration was 7 μs with a maximum source voltage of − 2400 V, which efficiently facilitated the ionization of the sputtered carbon species. In order to show the effectiveness of the short pulse operation, the fabricated DLC films were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. XPS spectra were curve-fitted using three Gaussian functions of sp3-C, sp2-C and C–O bonding. The information from the Raman and XPS spectra showed that the sp3 fraction in the DLC films fabricated using a pulse duration of 7 μs was larger than that obtained using a pulse duration of 50 μs. It was found that the sp3/sp2 ratio was larger than 40%, which was approximately 1.5-fold compared to that obtained using a pulse duration of 50 μs. A high sp3 fraction was realized due to application of high voltage without arc generation transferred from a magnetron sputtering (MS) glow discharge. To obtain the high sp3 fraction in the fabricated DLC films, a parametric survey was performed, in which the background gas pressure, bias voltage applied to the substrate, power-source voltage and the distance between the target and the substrate were varied. There were optimum deposition parameters for lowering the D-band and G-band intensity ratio (ID/IG) in Raman spectra. The optimum source voltage was in the range of − 1200 to − 1600 V. For voltages higher than − 1600 V, energetic carbon and argon ions may deteriorate the film properties. The hardness of the fabricated DLC films at 7-μs-pulse-width and − 1200 V source-voltage were obtained as 37 GPa measured with a nano-indenter. The hardness decreased to a range from 20 to 27 GPa with increasing the pulse width in range from 40 to 60 μs.