Wear properties of graphene edges probed by atomic force microscopy based lateral manipulation

Excellent elastic properties and good adhesion of graphene to substrate make graphene a promising candidate for application in various friction and wear protective coatings. In order to investigate the response of graphene edges on lateral forces, we combine atomic force microscopy (AFM) based experiments with large scale molecular dynamics (MD) simulations. Exploring movement of AFM tip across graphene edges, we identify four consecutive processes in the course of manipulation: a small increase of lateral force across graphene edges, elastic deformation, plastic deformation followed by permanent wrinkle formation and partial peeling from substrate, and graphene fracture followed by complete peeling within the scan area. In addition, on apexes of graphene flakes, we observe graphene folding followed by the formation of defect free edges. They can prevent further wear to some extent. MD simulations reveal that wrinkles initiated by AFM probe, grow over distance covered by the probe and they are responsible for the observed increase of the lateral force.