Disorder induced Coulomb gaps in graphene constrictions with different aspect ratios

TL;DR

This study investigates how disorder affects the electronic energy gaps in graphene nanoconstrictions with varying aspect ratios, revealing a length-independent disorder-induced gap that scales inversely with width and highlighting potential for tunneling applications.

Contribution

It provides new insights into disorder-induced energy gaps in graphene constrictions and explores how aspect ratio influences transport properties, especially in very short constrictions.

Findings

Disorder induces an effective energy gap around the charge neutrality point.

The energy gap scales inversely with the width of the constriction.

Very short constrictions show resonances and high conductance, useful for tunneling barriers.

Abstract

We present electron transport measurements on lithographically defined and etched graphene nanoconstrictions with different aspect ratios including different lengths (L) and widths (W). A roughly length-independent disorder induced effective energy gap can be observed around the charge neutrality point. This energy gap scales inversely with the width even in regimes where the length of the constriction is smaller than its width (L<W). In very short constrictions, we observe both resonances due to localized states or charged islands and an elevated overall conductance level (0.1-1e2/h), which is strongly length-dependent in the gap region. This makes very short graphene constrictions interesting for highly transparent graphene tunneling barriers.