Transport in coupled graphene-nanotube quantum devices

TL;DR

This paper presents the fabrication and characterization of hybrid graphene-nanotube quantum devices, demonstrating charge detection and Coulomb blockade phenomena, advancing all-carbon quantum device technology.

Contribution

It introduces novel all-carbon hybrid quantum devices with integrated graphene and nanotube components, including charge detection and tunneling properties.

Findings

Graphene nanoribbons effectively detect charging events in nanotube quantum dots.

Tunneling rates in the junction reach low GHz frequencies.

Coulomb blockade observed in nanotube quantum dots with graphene leads.

Abstract

We report on the fabrication and characterization of all-carbon hybrid quantum devices based on graphene and single-walled carbon nanotubes. We discuss both, carbon nanotube quantum dot devices with graphene charge detectors and nanotube quantum dots with graphene leads. The devices are fabricated by chemical vapor deposition growth of carbon nanotubes and subsequent structuring of mechanically exfoliated graphene. We study the detection of individual charging events in the carbon nanotube quantum dot by a nearby graphene nanoribbon and show that they lead to changes of up to 20% of the conductance maxima in the graphene nanoribbon acting as a good performing charge detector. Moreover, we discuss an electrically coupled graphene-nanotube junction, which exhibits a tunneling barrier with tunneling rates in the low GHz regime. This allows to observe Coulomb blockade on a carbon nanotube quantum dot with graphene source and drain leads.