Conductance gap induced by orbital symmetry mismatch in inhomogeneous hydrogen-terminated zigzag graphene nanoribbons

Abstract

Using the non-equilibrium Greens function method in combination with the density functional theory, we investigate the electronic transport properties of zigzag graphene nanoribbons (zGNRs) passivated with Hydrogen atoms. The coexistence of sp2-edges and sp3-edges in zGNRs can induce quite stable conductance gaps in a large range from 0 to 3.5eV, which can even occur in a wide zGNR with a width up to 10nm. We found that the orbital symmetry mismatch between the sections with sp2 and sp3 edges is responsible for the totally suppressed conductivity of the edge states, and the gap size is determined by the minimal energy difference between the second highest valence band and the second lowest conduction band of the corresponding sp2-edged ribbons. These findings provide a very attractive design and fabrication strategy for controlling the energy gap of graphene nanoribbons.