Deformation-leading load-dependent friction hysteresis of suspended graphene

Friction hysteresis, a common event in ultrathin two-dimensional materials, is significantly influenced by their deformation. This study explores the friction hysteresis of suspended graphene with varying thicknesses using atomic force microscopy (AFM) conducted under controlled humidity conditions. Compared with that in the supported case, the friction in the suspended graphene cases demonstrates significant hysteresis. The degree of friction hysteresis on suspended graphene increased with decreasing thickness and increasing relative humidity and cut-off load. Both deformation hysteresis and adhesion hysteresis contribute to the friction hysteresis of suspended graphene, with deformation hysteresis playing a dominant role. The finite element simulation revealed that the sliding process enhanced deformation and increased the contact area for the major friction hysteresis. The deformation hysteresis of suspended graphene expands the contact area and increases energy dissipation during unloading, resulting in significant friction hysteresis. These findings advance our understanding of friction hysteresis on graphene in terms of deformation hysteresis.