Deformation-leading load-dependent friction hysteresis of suspended graphene

Friction hysteresis, a common event on ultra-thin 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 to the supported case, friction demonstrates significant hysteresis in suspended graphene. The degree of friction hysteresis on suspended graphene increased with the decrease of thickness and the increase of 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 reveals that the sliding process enhanced deformation and increased 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 complete understanding of the friction hysteresis on graphene in terms of deformation hysteresis.