Structure, properties and growth mechanism of a self-assembled nanocylindrical MoS2/Mo-S-C composite film

A self-assembled nanocylindrical MoS2/M-S-C composite film with excellent tribological properties was synthesized by simultaneously sputtering of MoS2 and graphite targets. The HRTEM observation of the polished surface and cross-sections reveals that this nanocylindrical structure with MoS2-rich phase encircled by carbon matrix arranging alternately in vertical patterns is initiated from the film-substrate interface and continues to the film surface. The XRD results show that this film exhibits dominant (1 0 0) basal planes. In comparison with pure MoS2 film, this nanocylindrical MoS2/Mo-S-C composite film exhibits largely enhanced hardness and higher elastic recovery ratio (d(elastic)/d(max)) under the same load. Surprisingly, the pin-on-disk tribotests in vacuum on it display a low friction-coefficient and long wear lives (up to 5x10(5) revolutions). The HRTEM observation of wear tracks finds that the MoS2 texture was reassembled on the film surface, and a tribofilm with preferential (0 0 2) basal planes in thickness about 100 nm is quickly formed in sliding. Based on the XRD results and TEM images of this film, this clear nanocylindrical structure was attributed to atomic transport occurring preferentially along the edge sites of MoS2 crystallites.