Free Folding of Suspended Graphene Sheets by Random Mechanical Stimulation

Graphene edges, analogous to the structure of nanotubes, can significantly influence the overall electronic and magnetic properties of graphene nanostructures, and thus have become important issues in graphene research, especially for electronic applications. In this recent paper published on PRL, we reported that the free folding of suspended graphene sheets by random mechanical stimulation has preferred folding directions. Among ~100 folded graphene edges examined by electron nanodiffraction, about 1/3 are armchair and 1/3 are zigzag. We explored the energetics of graphene folding by atomic simulation. It is shown that armchair and zigzag edges correspond to two energy minima and thus dominate the graphene folding. The results can be explained by the atomic structures of folded graphenes. The zigzag edge has AB stacking (AB stacking is the lowest energy state between two parallel graphenes), while in the armchair edge, AB stacking is achieved in some areas by a small twist.