  The folding of monolayer graphene leads to new layered systems, termed
twisted bilayer graphene (TBG), generally displaying a certain interlayer
rotation away from crystallographic alignment. We here present an atomic force
microscopy study on folded graphene, revealing unexpectedly large twist angle
dependent modulations of ~3 angstrom in interlayer distance. At the TBG
surface, we find enhanced friction attributable to superlubricity in between
incommensurate layers. At the bended edge, the radius of curvature scales with
the folded length, congruent to earlier studies on carbon nanotubes.

Materials Science