Fracture of polycrystalline graphene membranes by <i>in situ</i> nanoindentation in a scanning electron microscope

Failure of polycrystalline graphene grown by chemical vapor deposition was investigated by nanoindentation in a scanning electron microscope. Circular graphene membranes were subject to central point loads using a nanomanipulator combined with an atomic force microscope cantilever as a force sensor. The grain boundaries of the polycrystalline graphene were visualized by Raman spectroscopy coupled with a carbon isotope labeling technique. Graphene membranes without any grain boundary had a failure strength of 45.4 ± 10.4 GPa, compared to 16.4 ± 5.1 GPa for those with grain boundaries when a Young's modulus was assumed to be 1 TPa. (© 2015 WILEY‐VCH Verlag GmbH &amp;Co. KGaA, Weinheim)