Improving the internal stress and wear resistance of DLC film by low content Ti doping

Low concentration Ti-doped hydrogenated amorphous carbon (Ti-C: H) films were deposited on silicon wafers by middle frequency magnetron sputtering titanium twin-targets in the feed gas of Ar/CH4. Ti concentration was controlled by varying the gas flow ratio of Ar/CH4 to be in the range of about 0.2–0.4 at.%. X-ray photoelectron spectroscopy (XPS), Raman and high-resolution transmission electron microscope (HRTEM) were used to analyze the composition and microstructure of the films. The internal stress, mechanical and tribological properties of the films were investigated by BGS 6341 type film stress tester, nanoindentation and reciprocating ball-on-disk tribo-tester, respectively. The results indicated that the incorporated Ti probably presents in the form of atomic state since no TiC was observed. The introduction of low content Ti significantly reduced the internal stress of DLC films with slight sacrifice of the hardness, and no obvious change was observed for the internal stress and hardness as the Ti content varies in the range of 0.2–0.42 at.%. Moreover, the low content Ti incorporation enhanced the friction and wear resistance of the DLC films dramatically with wear rate of ∼10−8 mm3/Nm and friction coefficient of 0.04. That is, no matter how much is Ti doping amount, the DLC film has excellent properties as long as the amount of Ti doping reaches the low content level.

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