The effects of defects on the conductance of graphene nanoribbons

The quantum conductance of graphene nanoribbons that include vacancy and adatom-vacancy defects is studied for both armchair and zigzag edge structures. The conductance is calculated by using the Green's function formalism combined with a tight-binding method for the description of the system. Our results reveal that, owing to the localized states that appear near the defect sites, the conductance of the defected nanoribbons generally decreases. We show that details of the conductance reduction depend on the structure of the defect, its distance from the ribbon edges, and the ribbon width. While some defect structures cause the conductance of the ribbon to vanish, some other defects have no effect on the conductance at the Fermi energy.