Tunable moir\'e bandgap in hBN-aligned bilayer graphene device with in-situ electrostatic gating

TL;DR

This study demonstrates direct visualization of tunable band gaps in hBN-aligned bilayer graphene using advanced spectroscopy, revealing how electrostatic gating and moiré potentials collaboratively modulate the electronic properties for device applications.

Contribution

It introduces a direct measurement method for band gap modulation in bilayer graphene and quantifies the effects of displacement fields and moiré potentials.

Findings

Electrostatic gating induces a band gap up to 100 meV.

Moiré potential adds approximately 20 meV to the band gap.

Theoretical models accurately reproduce experimental results.

Abstract

Over the years, great efforts have been devoted in introducing a sizable and tunable band gap in graphene for its potential application in next-generation electronic devices. The primary challenge in modulating this gap has been the absence of a direct method for observing changes of the band gap in momentum space. In this study, we employ advanced spatial- and angle-resolved photoemission spectroscopy technique to directly visualize the gap formation in bilayer graphene, modulated by both displacement fields and moir\'e potentials. The application of displacement field via in-situ electrostatic gating introduces a sizable and tunable electronic bandgap, proportional to the field strength up to 100 meV. Meanwhile, the moir\'e potential, induced by aligning the underlying hexagonal boron nitride substrate, extends the bandgap by ~ 20 meV. Theoretical calculations, effectively capture the experimental observations. Our investigation provides a quantitative understanding of how these two mechanisms collaboratively modulate the band gap in bilayer graphene, offering valuable guidance for the design of graphene-based electronic devices.