A Gate-Induced Switch in Zigzag Graphene Naoribbons and Charging Effects

TL;DR

This paper investigates the nonlinear transport and charging effects in gated zigzag graphene nanoribbons, revealing a robust negative differential resistance influenced by edge effects, aspect ratio, and impurities, with potential for high on/off current ratios.

Contribution

It introduces a detailed analysis of NDR in zigzag graphene nanoribbons using NEGF formalism, highlighting the effects of gating, edge charge transfer, and aspect ratio on electronic transport.

Findings

Negative differential resistance observed with high on/off ratio (~10^6)

NDR is robust against electrostatic screening near contacts

On/off ratio scales with ribbon length following a power law

Abstract

Using non-equilibrium Green's function formalism, we investigate nonlinear transport and charging effects of gated graphene nanoribbons (GNRs) with even number of zigzag chains. We find a negative differential resistance (NDR) over a wide range of gate voltages with on/off ratio $\sim 10^6$ for narrow enough ribbons. This NDR originates from the parity selection rule and also prohibition of transport between discontinues energy bands. Since the external field is well screened close to the contacts, the NDR is robust against the electrostatic potential. However, for voltages higher than the NDR threshold, due to charge transfer through the edges of ZGNR, screening is reduced such that the external potential can penetrate inside the ribbon giving rise to smaller values of off current. Furthermore, on/off ratio of the current depends on the aspect ratio of the length/width and also edge impurity. Moreover, on/off ratio displays a power law behavior as a function of ribbon length.