Experimental Decoding and Tuning Electronic Friction of Si Nanotip Sliding on Graphene

Due to the coupled contributions of adhesion and carrier to friction typically found in previous research, decoupling the electron-based dissipation is a long-standing challenge in tribology. In this study, by designing and integrating a graphene/h-BN/graphene/h-BN stacking device into an atomic force microscopy, the carrier density dependent frictional behavior of a single-asperity sliding on graphene is unambiguously revealed by applying an external back-gate voltage, while maintaining the adhesion unaffected. Our experiments reveal that friction on the graphene increases monotonically with the increase of carrier density. By adjusting the back-gate voltage, the carrier density of the top graphene layer can be tuned from -3.9 × 1012 to 3.5 × 1012 cm-2, resulting in a ∼28% increase in friction. The mechanism is uncovered from the consistent dependence of the charge density redistribution and sliding barrier on the carrier density. These findings offer new perspectives on the fundamental understanding and regulation of friction at van der Waals interfaces.