Folded graphene membranes: mapping curvature at the nanoscale.

While the unique elastic properties of monolayer graphene have been extensively investigated, less knowledge has been developed so far on folded graphene. Nevertheless, it has been recently suggested that fold-induced curvature (without in-plane strain) could possibly affect the local chemical and electron transport properties of graphene, envisaging a material-by-design approach where tailored membranes are used in enhanced nanoresonators or nanoelectromechanical devices. In this work we propose a novel method combining apparent strain analysis from high-resolution transmission electron microscopy (HREM) images and theoretical modeling based on continuum elasticity theory and tight-binding atomistic simulations to map and measure the nanoscale curvature of graphene folds and wrinkles. If enough contrast and resolution in HREM images are obtained, this method can be successfully applied to provide a complete nanoscale geometrical and physical picture of 3D structure of various wrinkle and fold configurations.