Effect of the Contact Geometry on Nanoscale and Subnanoscale Friction Behaviors

Stick-slip motion is the most well-known phenomenon in nanotribology. Maier et al. previously studied the dependence of slip time on contact geometry. In their paper, they were able to identify the intermediate state during slip motion. However, detailed study of this intermediate state is difficult due to the fast dynamics. The advantage of molecular dynamics (MD) simulation is that it can provide detailed information and direct visualization of the tribological phenomena on a time scale of a few nanoseconds. In this paper, we investigate the detailed mechanism of stick-slip motion in nanoscale. MD simulation precisely mimics friction force microscopy experiments. In MD simulations, a crystalline Si tip slides on a graphene surface, and the tip size is varied. The simulation results provide evidence of the intermediate state during slip motion and reveal the hierarchical structure of the stick-slip motion in nanoscale. Detailed relations among stick-slip motion, contact geometry, and energy state are also analyzed.