Nanoscratching of multi-layer graphene by molecular dynamics simulations

• Nanoscratching behavior of multi-layer graphene was investigated by MD simulation.
• Graphene has superlow friction coefficient with scratch depth less than 5.3 Å.
• Friction coefficient increases at least 10 times with further scratch depth.
• Phase transition of graphene leading to the increment of friction coefficient.
• Friction coefficient is sensitive to the shape of scratch tip and its anisotropy.

Graphene or graphene-based materials are becoming a glowing material to be expected to control a frictional behavior at contact interface. However, due to its atomic layer to layer structure, it is difficult to clarify its frictional mechanism through experimental observation. Therefore, in this paper the frictional behavior of diamond tip nanoscratching on multi-layer graphene was investigated by Molecular Dynamics (MD) simulation. Results show superlow frictional behavior of graphene layers when the scratch depth is less than 5.3 Å, when the scratch depth is over this value, the friction coefficient increases at least 10 times which is caused by phase transition of graphene layers. Besides, we discussed the sensitivity of friction coefficient to the shapes of scratch tip and its anisotropy.