Charge carrier transport across grain boundaries in graphene

We evaluate the charge carrier transmission across asymmetric grain boundaries (GB) in a graphene lattice within the Landauer-Buttiker formalism. We employ a tight-binding model for C-based materials that accounts for lattice strain introduced by topological defects, such as grain boundaries. In particular, we investigate electronic transmission across grain boundaries found to be stable up to high temperatures. Our calculations suggest that the introduction of GBs generally preserves the zero-transport gap property of pristine graphene. However, only some specific asymmetric GBs open a moderate transport gap, which can be as high as ≈ 1.15 eV. We find that the GBs that introduce a transport gap are characterized by the existence of a mismatch along the GB. Indeed, the magnitude of this mismatch appears to be the main structural variable that determines the transport gap size, with greater mismatch resulting in larger transport gaps. Finally, we find that the presence of GBs reduces considerably electron transmission, and less so hole transmission.