Local Spectroscopy of the Electrically Tunable Band Gap in Trilayer Graphene

TL;DR

This study uses local spectroscopy to explore how stacking order affects the tunable electronic properties of trilayer graphene, revealing significant spatial variations due to impurities.

Contribution

It provides spatially-resolved measurements of the electric field tunable band gap in different stacking orders of trilayer graphene, highlighting impurity effects.

Findings

ABC trilayer graphene exhibits a widely tunable band gap.

Charged impurities cause spatial fluctuations in the gap size.

ABA trilayer remains metallic regardless of electric field.

Abstract

The stacking order degree of freedom in trilayer graphene plays a critical role in determining the existence of an electric field tunable band gap. We present spatially-resolved tunneling spectroscopy measurements of dual gated Bernal (ABA) and rhombohedral (ABC) stacked trilayer graphene devices. We demonstrate that while ABA trilayer graphene remains metallic, ABC trilayer graphene exhibits a widely tunable band gap as a function of electric field. However, we find that charged impurities in the underlying substrate cause substantial spatial fluctuation of the gap size. Our work elucidates the microscopic behavior of trilayer graphene and its consequences for macroscopic devices.