▎ 摘　　要

Using the non-equilibrium Green's function method together with the density-functional theory, the electronic transport properties of heterojunction models constructed with armchair and zigzag graphene nanoribbon (GNR) units via topological defects have been investigated. It is found that the diode-like behavior and conductivity of the armchair9-zigzag4 (A9-Z4) junctions are associated with the length of the nanoribbon sub-units closely. The structure similar to the p-n junction is formed around the defect region, inducing the rectifying property of the model. Moreover, the conductivity of symmetrical heterojuction structures can be optimized by controlling the length of GNR units. (C) 2014 Elsevier B.V. All rights reserved.