▎ 摘　　要

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 tope 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. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim