▎ 摘　　要

Step-like zigzag graphene nanoribbons (ZGNRs) with different step widths are designed, and their electronic transport properties are investigated by using the non-equilibrium Green's function method combined with the density functional theory. The results reveal that one with a small step structure can exhibit better conductive capability and interesting negative differential resistance (NDR) behavior under negative applied biases. More importantly, with the increase of step width, these step-like ZGNR nanojunctions present valuable rectification effects, and show a rule that the rectification ratio increases with increasing the step width. It is also shown that the rectification effect can be further inversed and enhanced through introducing a defect around the step. Transmission spectra, densities of states, energy barriers, transmission eigenstates, and transmission pathways are analyzed subsequently to understand the electronic transport properties of these step-like ZGNR devices, which can be used in developing nanoscale NDR devices and rectifiers. (C) 2014 Elsevier B.V. All rights reserved.