Tribological properties of diamond-like carbon films prepared by mass-separated ion beam deposition

Abstract

Carbon films were prepared by mass-separated ion beam deposition (MSIBD) with a high ion beam current density of 0.2 mA/cm2 under a ultra-high vacuum pressure of 10−7 Pa. The dependence of the sp3 bond fraction and the tribological properties on the ion beam energy was investigated. The maximum value of the sp3 bond fraction was 84%, which was obtained at the ion energy between 75 and 100 eV. The hardness and the Young's modulus of the carbon films were determined by a nanoindentation test, and these properties showed the same dependence of the sp3 bond fraction on the ion energy. A maximum hardness of 80 GPa and a modulus of 740 GPa were obtained at the ion energy of 100 eV. The friction coefficient was not dependent on the ion energy and showed a low value between 0.08 and 0.1. The low friction coefficient of obtained films was due to the homogeneous amorphous structure and very smooth surface of films. The wear rate showed the same dependence of the sp3 bond fraction on the ion energy and a minimum value of 6.01×10−9 mm3/Nm at the ion energy of 100 eV. The wear resistance was related to the sp3 bond fraction and the hardness of films.