Effects of structural characteristics of Cu grain boundaries on graphene growth

Abstract

The grain structure of graphene significantly affects its properties; therefore, controlling the grain structure is crucial for the application of graphene. Previous investigations have shown inconsistent results regarding the correlation between the grain structures of graphene and the underlying Cu. We investigated the origin of this discrepancy by analyzing the effects of the structural characteristics of the Cu grain boundaries on graphene growth in polycrystalline Cu micropatterns defined by a lithographically patterned SiO2 mask layer. The number densities of the graphene grains are statistically characterized to be smaller than those of Cu grains, suggesting that graphene nuclei grow across some Cu grain boundaries without changing their orientations. It is shown that such growth is more likely to occur across low-angle and Σ3 twin boundaries, while random high-angle grain boundaries can significantly affect the growth rate and edge orientation of graphene islands, presumably leading to the correlation between the grain structures of Cu and graphene. It is suggested that this difference is the origin of the abovementioned discrepancy and is explained in terms of deeper grooves with a large number of atomic steps in random high-angle grain boundaries, which increase the diffusion distance and activation barrier for the surface diffusion of carbon.