The Origin of Moiré-Level Stick-Slip Behavior on Graphene/h-BN Heterostructures

Frictional behavior of a nanoscale tip sliding on superlattice of aligned graphene/(hexagonal boron nitride) h-BN heterostructure is found to be strongly regulated by the moiré superlattices, resulting in long-range stick-slip modulation in experimental measurements. Through molecular dynamics simulations, it is shown that the origin of moiré-level stick-slip comes from the strong coupling between in-plane deformation and out-of-plane distortion of the moiré superlattice. The periodicity of long-range modulation decreases as the interfacial twist angle increases, once the periodicity of moiré becomes smaller than the contact region between the tip and graphene, the long-range modulation becomes smooth and the stick-slip behavior disappears. It is found that the contact trajectory of the tip during sliding is the key to reveal the underlying mechanism, based on which a modified Prandtl-Tomlinson model is proposed considering deformation coupled effect to reproduce the frictional properties observed in molecular dynamics simulation. These findings emphasize the critical role of the moiré superlattice on frictional properties of van der Waals (vdW) heterostructures and open an avenue for the rational design of vdW devices with controllable tribological properties.