Microstructure and properties of Mo doped DLC nanocomposite films deposited by a hybrid sputtering system

Abstract

A combination of low internal stress and hydrophobic performance for carbon film is crucial in some practical applications. In this work, Mo doped diamond-like carbon (DLC) films were deposited by a hybrid coating system. The designed DLC films with various Mo contents were obtained by adjusting the Mo target powers. The microstructure and comprehensive properties including wettability of Mo-DLC films were analyzed systematically. Results showed that with increasing the Mo target power, Mo content and deposition rate of films were continuously increased, and also the surface roughness slightly increased. At low Mo doping, films mainly exhibited amorphous feature, whereas, the MoC nanocrystallites were found at high Mo doping, implying the nanocomposite structure formed where MoC crystals were embedded in the carbon matrix. The sp3-C bond fraction was decreasing with increasing the Mo content due to the metal catalyst effect, which effectively promoted the sp3-C bonds transforming into sp2-C bonds. Meanwhile, the Mo addition had a significant positive effect on the reduction of residual stress. Moreover, the wettability of films was transferred from hydrophilicity state to hydrophobicity state, and the maximum water contact angle was 94.2° at 20.1 at. % Mo doping, then slightly diminished to 92.7° with further increasing Mo content. The present work would offer an available method to fabricate the DLC film with low internal stress and desirable wettability property.