Quantum Transport Characteristics of Graphene Nanoribbon Devices with Ring and Ladder Type Channels Under Electrostatic Doping

Abstract

The electronic transmission properties of two-terminal graphene nanoribbon (GNR) devices, featuring ring and ladder geometries with varying sizes, are investigated to understand the influence of explicit charge doping on their electrostatic control. The results indicate that explicit charge doping affects the device behavior, from single electron transport to resonant transport for different channels. When charge doping is applied, it induces quantum dot formation electrostatically, causing the ladder-type channel GNR with a channel length of 49.7 & Aring; to function similarly to a quantum dot. Therefore, this smallest ladder type channel shows current oscillations which are attributed to single-electron tunneling. As the channel length increases in ladder-type devices, a current path develops within the channel, forming a conductive path in larger devices that results in significant current and eliminates the tunneling barrier effect. On the other hand, for the ring-shaped GNRs, it is found that the transport behavior gradually shifts from an antiresonant to a resonant transport regime with increasing radius under explicit charge doping. These results show a strong competition between quantum-confinement effects and quantum dot-to-electrode coupling for both geometries when explicit charge doping is applied.