Atomic roughness enhanced friction on hydrogenated graphene.

Atomic friction on hydrogenated graphene is investigated using molecular dynamics simulations. Hydrogenation is found to increase friction significantly, and the atomic-level information provided by the simulations reveals that atomic roughness induced by hydrogenation is the primary cause of the friction enhancement. Other proposed mechanisms, specifically adhesion and rigidity, are excluded based on the simulation results and analyses performed using the Prandtl-Tomlinson model. In addition, it is found that friction does not monotonically increase with hydrogen coverage on the graphene surface; instead, a maximum friction is observed at a hydrogen coverage between 5 and 10%.