The periodicity in interfacial friction of graphene

The interfacial friction of graphene transferred on a SiO2 grating was investigated using a lateral force microscope with various sliding directions. Quantification of the frictional force of graphene, using adhesion force and friction loop measured from both sloped and flat surfaces, revealed that graphene has a low surface energy and repetitive friction switching from 0.066 to 0.087, which indicates an extremely low shear strength of the contact junction, along with a peculiar periodicity of 60°, which is consistent with the lattice periodicity of graphene. The observed periodicity was attributed to the atomistic incommensurability at the interface, with minimal lattice deformation under interfacial sliding conditions.