Abstract

 A single crystal graphene film grown on a Cu(111) foil by chemical vapor deposition (CVD) has ribbon-like fold structures. These graphene folds are highly-oriented and essentially parallel to each other. Cu surface steps underneath graphene are along the <110> and <211> directions, leading to the formation of the arrays of folds. The folds in the single layer graphene (SLG) are not continuous but break up into “alternating” patterns. A“joint” (an AB-stacked bilayer graphene) region connects two neighboring alternating regions, and the breaks are always along zigzag or armchair directions. Folds formed in bilayer or few-layer graphene are continuous with no breaks. Molecular dynamics simulations show that SLG suffers a significantly higher compressive stress compared to bilayer graphene when both are under the same compression, thus leading to the rupture of SLG in these fold regions. The fracture strength of a CVD-grown single crystal SLG film was simulated to be about 70 GPa. This study greatly deepens the understanding of the mechanics of CVD-grown single crystal graphene and such folds, and sheds light on the fabrication of various graphene origami/kirigami structures by substrate engineering. Such oriented folds can be used in a variety of further studies.