▎ 摘　　要

We propose two schemes for a field-effect transistor based on gapped armchair graphene nanoribbons connected to metal leads, by introducing side-arms or on-site gate voltages. We make use of the band gap to reach excellent switch-off characteristics. Introduction of one side-arm or on-site gate to the graphene nanoribbon causes conduction peaks to appear inside the gap regime. By further application of two side-arms or on-site gates, these peaks are broadened to conduction plateaus with a wide energy window, thanks to the resonance from the dual structure. The position of the conduction windows inside the gap can be fully controlled by the length of the side-arms or the on-site gate voltages, which allows "on" and "off" operations for a specific energy window inside the gap regime. The high robustness of both the switch-off character and the conduction windows is demonstrated and shows the feasibility of the proposed dual structures for real applications.