Effect of Local Terrace on Structure and Mechanics of Graphene Grain Boundary

In this study, the effects of local terrace of the substrate on the structure and mechanical properties of graphene grain boundaries (GBs) during chemical vapor deposition (CVD) growth have been explored by phase-field crystal modeling and molecular dynamics simulations. It is found the GBs are significantly disturbed for a weak surface disturbance with a bulge height of only 3.4 Å. The distance between GBs and the bulge plays an important role in determining the morphologies of GBs, and the aperiodic and curved GBs can be observed, which is attributed to several representative structures, like 5-6|6-7 and 5-6-7 defects and GB deflection. In general, there are four fracture modes for GBs with weak surface disturbance depending on the existence of 5-6-7 and 5-6|6-7 defects. While for a strong surface disturbance with a bulge height of 10 Å, the interaction between topological defects at bulged graphene and GBs will locally offset nearby 5-7 dislocation pairs, and there are two fracture modes depending on the structural integrality of GBs. Besides, it is also found that the aperiodic and curved morphologies of GBs widely exist for other orientation angles with surface disturbance. The results presented herein explore the mechanism for the interaction of GBs with surface disturbance during CVD growth and may provide some useful insights for designing and regulating the morphologies of GBs. © 2019 American Chemical Society.