Electrically Tunable Friction at Two-Dimensional Heterointerface

Two-dimensional (2D) heterostructures with outstanding frictional properties have sparked immense interest in the field of tribology. Here, graphene oxide (GO)-coated conductive probes were fabricated, and the frictional behavior of the GO/graphene heterointerface under varying bias voltages was investigated using conductive atomic force microscopy. The friction at the GO/graphene interface increases with applied bias, enabling real-time and reversible control within a low-bias regime. Owing to the dielectric property of GO and the electrical conductivity of graphene, charges accumulate at the interface. Because atomically thin thickness of 2D materials, the accumulated charges produce a large interfacial electrostatic force for stable friction control. However, the stability of this control decreases when high positive bias is applied. Scanning Kelvin probe microscopy and adhesion measurements indicate that strong electric fields enable a fraction of the accumulated electrons to tunnel through the GO barrier, thereby altering the interfacial electrostatic interactions. In contrast, high negative bias voltages induce electrochemical oxidation of graphene to varying extents, resulting in a permanent and substantial friction modulation. These findings advance the fundamental understanding of friction in 2D heterointerfaces and provide important insights for friction regulation and the development of electrically tunable smart tribological systems.