LAUSR

Graphene has excellent lubricity because of its layer-stacking structure. However, after most fabricating processes, steps appear on the surface of graphene and can significantly affect its lubrication performance. Experimental studies often scratch the tip of Atomic force microscopy (AFM) on graphene to study the friction properties of graphene. Unfortunately, the friction mechanism between tips and graphene step edges is still unclear, especially when the effect of tip shape on friction at graphene edges is considered. This paper investigated the atomic friction at graphene step edges considering a new tip shape model: a cone of which the top is the sphere. First, each type of parameters of tip shape was discussed in detail to determine how they can influence the friction behavior at graphene step edges. Then, molecular dynamics (MD) simulation was used to analyze the specific changes of friction and graphene morphology with different parameters of tip shape. The results showed that the shape parameters have considerable effects on friction behavior during the tip slides on the graphene step edges. Therefore, this study can be used to design the tip shape for further investigation on the friction properties of graphene. More importantly, this paper is a good beginning of modeling tip shape considering physical effects rather than simple hemispheroid in MD simulations.