Friction-Load Relationship in the Adhesive Regime Revealing Potential Incapability of AFM Investigations

Reduced friction with increasing normal load in the adhesive regime is revealed by vdW-corrected DFT calculations of various rigid junction models such as Graphene/Graphene, h-BN/h-BN, and Graphene/h-BN. The origin of the friction-load relationship arises from the decreased sliding potential corrugation with increased normal load in the attractive regime of the interfacial separation above its equilibrium. The negative coefficient of friction behavior, which is mainly dominated by van der Waals attraction, is expected to appear in many interfaces without significant deformation. However, the friction behavior presented here may be inaccessible to atomic forces microscope (AFM) due to the intrinsic instability. The instruments such as interfacial forces microscope with force-feedback sensor or quartz tuning forks with large stiffness are proposed to measure friction behaviors in the entire attractive region.