Transport spectroscopy of disordered graphene quantum dots etched into a single graphene flake

TL;DR

This study investigates how disorder affects electronic properties in graphene quantum dots of different sizes, revealing size-dependent transport gaps and energies, with implications for understanding localization and spin behavior in disordered graphene systems.

Contribution

It provides the first systematic comparison of transport properties in graphene quantum dots of various sizes etched into a single flake, emphasizing the role of disorder and confinement.

Findings

Transport gaps and addition energies increase as dot size decreases.

Disorder-induced localization is the dominant physical mechanism.

Measured g-factor is consistent with g=2 within error bars.

Abstract

We present transport measurements on quantum dots of sizes 45, 60 and 80 nm etched with an Ar/O2-plasma into a single graphene sheet, allowing a size comparison avoiding effects from different graphene flakes. The transport gaps and addition energies increase with decreasing dot size, as expected, and display a strong correlation, suggesting the same physical origin for both, i.e. disorder-induced localization in presence of a small confinement gap. Gate capacitance measurements indicate that the dot charges are located in the narrow device region as intended. A dominant role of disorder is further substantiated by the gate dependence and the magnetic field behavior, allowing only approximate identification of the electron-hole crossover and spin filling sequences. Finally, we extract a g-factor consistent with g=2 within the error bars.