Effects of adding hydrocarbon gas to a high-power impulse magnetron sputtering system on the properties of diamond-like carbon films

Diamond-like carbon (DLC) films were prepared via reactive high-power impulse magnetron sputtering (HiPIMS) using a mixture of argon and a small amount of C2H4 or CH4 gas. Synthesis of the DLC films was based on both plasma-enhanced chemical vapor deposition and physical vapor deposition. At a peak target current of 30 A corresponding to 1.1 A/cm(2), the hardness of films prepared with hydrocarbon gas fractions of less than 5% was somewhat higher than the hardness of films prepared via nonreactive Ar HiPIMS. The absence of background due to photoluminescence in the Raman spectra indicated that the hydrogen contents in the films were less than 20%. X-ray photoelectron spectroscopy (XPS) was performed, and the peaks related to the sp(3)C in the C is core level spectra were investigated. The sp(3)C peaks in the C is spectra of the films prepared at hydrocarbon gas fractions below 5% were more intense than sp(3)C related peaks in the spectra of the films prepared via nonreactive HiPIMS. The sp(3)C related peaks accounted for more than 30% of the total at a peak target current of 30 A. The influence of the target current on film properties was also investigated. At peak values of target current exceeding 40 A, the hardness of the films prepared via the nonreactive HiPIMS was somewhat higher than that of the films prepared via reactive HiPIMS. This was predicted from the relationship between the target current and the sp(3)C content estimated from the XPS spectra.