Charge-carrier transmission across twins in graphene

Twinning is a known accommodation mechanism of graphene that results in low-energy microstructures or twins. In view of their mechanical stability, twins suggest themselves as a possible means of introducing extended defects in graphene leading to the opening of transmission band gaps. We investigate charge-carrier transmission across the twin structures in graphene using the Landauer-Büttiker (LB) formalism in combination with a tight-binding model. We verify the approach by means of selected comparisons with density functional theory (DFT) and non-equilibrium Green's function (NEGF) calculations using the code SIESTA and TRANSIESTA. The calculations reveal that graphene twins open transport gaps depending on the twin geometry up to maximum of 1.15 eV. As previously reported for grain boundaries, we find that localized states arise at dislocation cores in the twin boundaries that introduce peaks near the Fermi level.