Electron transport in bilayer graphene nano constrictions patterned using AFM nanolithography

TL;DR

This study demonstrates that AFM nanolithography can create ultra-narrow bilayer graphene constrictions exhibiting quantum dot behavior, with potential applications in quantum electronics and spintronics.

Contribution

It introduces electrode-free AFM-LAO nanolithography as a precise, reproducible method for fabricating tunable graphene nanostructures with quantum confinement effects.

Findings

Narrow constrictions show a transport gap.

Quantum dots with addition energies >100 meV are formed.

Technique enables flexible, patternless nanostructure fabrication.

Abstract

Here we report on low temperature transport measurements of encapsulated bilayer graphene nano constrictions fabricated employing electrode-free AFM-based local anodic oxidation (LAO) nanolithography. This technique allows for the creation of constrictions as narrow as 20 nm much smaller than previous studies. In wider constrictions, we observe bulk transport characteristics. However, as the constriction's width is reduced, a transport gap appears. Single quantum dot (QD) formation is observed within the narrowest constriction with addition energies exceeding 100 meV, which surpass previous experiments on patterned QDs. Our results suggest that transport through these narrow constrictions is governed by edge disorder combined with quantum confinement effects. Our findings introduce electrode-free AFM-LAO lithography as an easy and flexible method for creating nanostructures with tunable electronic properties without relying on patterning techniques such as e-beam lithography. The excellent control and reproducibility provided by this technique opens exciting opportunities for carbon-based quantum electronics and spintronics.