Tunable quantum dots from atomically precise graphene nanoribbons using a multi-gate architecture

TL;DR

This paper demonstrates a multi-gate architecture for graphene nanoribbons that enables precise electrostatic control of quantum dots, advancing the development of tunable GNR-based quantum devices.

Contribution

Introduction of a multi-gate FET design with ultra-narrow finger gates for atomically precise GNRs, enabling differential tuning of quantum dots.

Findings

Quantum dot behavior observed with Coulomb diamonds.

Multi-gate control allows differential tuning of GNR quantum dots.

High-resolution lithography enables ultra-narrow gate fabrication.

Abstract

Atomically precise graphene nanoribbons (GNRs) are increasingly attracting interest due to their largely modifiable electronic properties, which can be tailored by controlling their width and edge structure during chemical synthesis. In recent years, the exploitation of GNR properties for electronic devices has focused on GNR integration into field-effect-transistor (FET) geometries. However, such FET devices have limited electrostatic tunability due to the presence of a single gate. Here, we report on the device integration of 9-atom wide armchair graphene nanoribbons (9-AGNRs) into a multi-gate FET geometry, consisting of an ultra-narrow finger gate and two side gates. We use high-resolution electron-beam lithography (EBL) for defining finger gates as narrow as 12 nm and combine them with graphene electrodes for contacting the GNRs. Low-temperature transport spectroscopy measurements reveal quantum dot (QD) behavior with rich Coulomb diamond patterns, suggesting that the GNRs form QDs that are connected both in series and in parallel. Moreover, we show that the additional gates enable differential tuning of the QDs in the nanojunction, providing the first step towards multi-gate control of GNR-based multi-dot systems.