C60 Filling-Enabled Tribological Improvement of Graphene in Conformal Contact with a Rough Substrate

Graphene has great potential in the field of solid lubricity due to its superlow friction and high wear resistance. However, the excellent tribological performance of graphene is degraded when it conformally contacts with a rough substrate. This work proposes a novel method to improve the tribological performance of graphene on a rough Si/SiO2 substrate by filling grooves on the substrate surface with C60 molecules. When C60 filling is not performed, the friction force on the graphene surface increases rapidly at the groove edges where graphene presents large out-of-plane deformation due to its conformal contact with the substrate. Inspiringly, such high friction force is reduced by one order of magnitude when C60 filling is introduced to provide out-of-plane support to graphene for preventing its conformal contact with the substrate. Meanwhile, the high mechanical strength of C60 molecules enables a greater than 5-fold strengthening of the load-carrying capacity of graphene, which greatly improves its wear resistance on the rough substrate. These observations are helpful in promoting the tribological application of graphene by diminishing its conformal contact with the rough substrate.