Self-organized transfer film-induced ultralow friction of Graphene/MoWS4 heterostructure nanocomposite

We report the tribological performance evaluation of Graphene/MoWS4 heterostructure nanocomposite prepared via simple spin-coating to lubricate the silicon-based MEMS devices. The lubrication mechanism of the nanocomposite was studied by a ball-on-disk tribometer, a three-dimensional surface profilometer, and high-resolution characterization techniques. The results show that the coefficient of friction was reduced from 0.4 to an ultralow friction level (mu similar to 0.02), and the specific wear rate of the silicon substrate was reduced by 3 orders of magnitude due to the lubricating effect and formation of transfer film of the nanocomposite. High-resolution characterization confirmed the formation of beneficial transfer film, indicating that the nanostructured graphene and MoWS4 were completely mixed in the transfer film. The transfer film enables the formation of low-friction contact by transferring the direct interaction of steel/silicon into an easy sliding steel/transfer film/silicon contact. Furthermore, the particular stacking and orientation of the nanosheets revealed the structural mechanism of ultralow friction.