▎ 摘　　要

Graphene nanoribbons with armchair edges (AGNRs) have bandgaps that can be flexibly tuned via the ribbon width. A junction made of a narrower AGNR sandwiched between two wider AGNR leads was recently reported to possess two perfect transmission channels close to the Fermi level. Here, we report that by using a bias voltage to drive these transmission channels into the gap of the wider AGNR lead, we can obtain a negative differential resistance (NDR) effect. Owing to the intrinsic properties of the AGNR junctions, the on-set bias reaches as low as similar to 0.2V and the valley current almost vanishes. We further show that such NDR effect is robust against details of the atomic structure of the junction, substrate, and whether the junction is made by etching or by hydrogenation. (C) 2015 AIP Publishing LLC.