Gate Voltage-Modulated Conductance in Zigzag Graphene Nanoribbon Junctions

Abstract

Using the Green’s function method, we study the modulation of the conductance in zigzag graphene nanoribbon (ZGNR) junctions by the gate voltages. As long as the difference between the gate voltages applied on the left and right ZGNRs (ΔV) remains unchanged, the conductance profiles for different cases are exactly the same, except to a displacement along EF-axis. It is found that the transmission of electrons from the upper/lower edge state of the left ZGNR to the lower/upper edge state of the right ZGNR is forbidden, therefore, the width of the conductance gap increases first and then decreases as |ΔV| increases. The upper/lower edge states and conduction/valence subbands of ZGNR under higher/lower gate voltage (VH/VL) determine step positions of the conductance when EF >VH/EF < VL. But when VL ≤ EF ≤ VH, the conductance profile is mainly determined by the upper and lower edge states, a few lowest conduction subbands/topmost valence subbands of ZGNR under lower/higher gate voltage. These results are helpful to the exploration and application of a new kind of field effect transistor based on ZGNR junctions.