Figure 3. The rupture processes of polycrystalline graphene for the different indentation locations.

The indenter tip is positioned on (a) grain center, (b) the same as (a) but with a hole at a GB junction, (c) GB, (d) GB junction, and (e) hole, respectively. The dotted circles indicate the initial crack formation. The close-up views of these crack formations are shown in the right panels. For clarity, the indenter tip is not shown. The rupture of polycrystalline graphene starts from a GB when the indenter tip is positioned on the center of grain, while the rupture of polycrystalline graphene starts directly from a defect when the indenter tip is positioned on the defect. Evidently, the failure behavior of polycrystalline graphene is dependent on the indentation location.