Velocity and temperature dependent adhesion and friction in mesoscale graphite contacts

Abstract

The weak interlayer binding in two-dimensional layered materials such as graphite has been the subject of intensive experimental investigation and modeling for structural superlubric and electronic devices. Yet, the effects of sliding velocity and temperature on the interfacial lateral forces in mesoscale contacts are poorly understood. Here, we report experiments of friction and adhesion forces in atomically pristine mesoscopic superlubric graphite, conducted over a range of sliding velocities and temperatures. It is shown that the friction force, temperature, and velocity follow the linear correlation of (Fc−F)3/2/T vs ln(v/T), which intriguingly aligns well with the thermally activated Prandtl–Tomlinson model associated with single asperity contacts. Moreover, when the velocity is lower than 2500 nm/s and the friction force approaches zero, the adhesive force increases with velocity and decreases with increasing temperature, indicating a thermally activated exfoliation process. Our results demonstrate that in cases where the interface is constrained to be atomically flat, mesoscale contacts can manifest single asperity force characteristics, where the sliding interface is collectively affected by thermal energy.