Graphene Nanoribbons with Smooth Edges Behave as Quantum Wires

TL;DR

This paper demonstrates that graphene nanoribbons with smooth edges act as high-quality quantum wires, exhibiting quantum transport phenomena and intrinsic bandgaps, contrasting with previous rough-edged nanoribbons dominated by defects.

Contribution

It reports the fabrication of graphene nanoribbons with smooth edges that behave as clean quantum wires, showing quantum phenomena and intrinsic bandgaps not seen in rough-edged counterparts.

Findings

Observation of Coulomb blockade and Kondo effect in nanoribbons

Presence of intrinsic quantum-confined bandgaps

High conductivities indicating defect-free behavior

Abstract

Graphene nanoribbons with perfect edges are predicted to exhibit interesting electronic and spintronic properties, notably quantum-confined bandgaps and magnetic edge states. However, graphene nanoribbons produced by lithography have, to date, exhibited rough edges and low-temperature transport characteristics dominated by defects, mainly variable range hopping between localized states in a transport gap near the Dirac point. Here, we report that one- and two-layer nanoribbons quantum dots made by unzipping carbon nanotubes10 exhibit well-defined quantum transport phenomena, including Coulomb blockade, Kondo effect, clear excited states up to ~20meV, and inelastic co-tunnelling. Along with signatures of intrinsic quantum-confined bandgaps and high conductivities, our data indicate that the nanoribbons behave as clean quantum wires at low temperatures, and are not dominated by defects.