Z-like Conducting Pathways in Zigzag Graphene Nanoribbons with Edge Protrusions

Electronic transport properties of zigzag graphene nanoribbons (ZGNRs) with one or two triangle protrusions at the edges are studied by using density functional theory combined with nonequilibrium Green's function method. We find the protrusion generally breaks down the edge state along the same edge, which carries the most current in the junction. For the graphene ribbons having even number of zigzag chains, however, the protrusions can increase or decrease significantly the conductance with different relative position of the two protrusions, accompanied by negative differential resistance characteristics. The abnormal increase of the conductance is ascribed to the forming of a new Z-like conducting pathway as well as the ruining of the mirror symmetry of the ribbons. In terms of odd ZGNRs, the introduction of edge protrusions only suppresses current flow and linear I-V curves are achieved. These edge-modified ways make the graphene-based nanomaterials present more abundant electronic transport phenomena and can be useful for the design of future nanoelectronic devices.