The mechanisms of friction enhancements on graphene surfaces with folds: The reinforcement of atomic pinning or attraction

Abstract The nano-friction behaviors of surfaces with a graphene fold (GF) oriented ~90° to the scanning direction were studied via an atomic force microscope. The GF exhibited dramatic friction increases at folding edges and modest friction augments at the folded area. Assisted with molecular dynamics simulations, we reproduced the experimental phenomena and elucidated that the substantial friction augments at the folding edge are attributed to enhanced pinning effects in front of the tip resulted from geometry barriers. The contact quality of interfaces at the fold-over structures is improved by an increase in the number of local pinning atoms in front of the tip or strengthened attraction of graphene to the back of the tip, leading to modest friction increases.