# Nanoscale Band Gap Modulation and Dual Moiré Superlattices of Hexagonal Boron Nitride Weakly Coupled to Graphite

## TL;DR

This paper explores how moiré patterns in hexagonal boron nitride/Graphite heterostructures can modulate electronic properties like band gap and work function at the nanoscale.

## Contribution

The study reveals dual moiré superlattices and significant electronic property modulations in weakly coupled h-BN/Graphite heterostructures.

## Key findings

- STM reveals large moiré patterns (14.8–18.3 nm periodicity) with local stacking variations.
- Spectroscopic data show 330 meV work function and 170 meV band gap modulations per moiré unit cell.
- Dual moiré superlattices in twisted h-BN/Graphite layers offer additional tunability for electronic properties.

## Abstract

Van der Waals (vdW) materials, such as hexagonal boron
nitride
(h-BN), are highly promising for applications in optoelectronics and
quantum technologies. When assembled into heterostructures, h-BN can
form moiré superlattices, enabling the engineering of electronic
and optical properties by varying the interlayer twist angle. However,
understanding the nanoscale interplay between moiré patterns
and electronic properties such as the band gap or work function, particularly
in optically active h-BN structures, remains a challenge. Here, we
use the atomic-scale precision of scanning tunneling microscopy (STM)
to uncover the role of moiré superlattices in the electronic
properties of a weakly coupled h-BN/Graphite heterostructure. Our
STM study reveals large moiré patterns (14.8–18.3 nm
periodicity) on the surface, implying slight local variations in the
h-BN/Graphite stacking throughout the sample. Spectroscopic measurements
show significant modulations of 330 meV in the local work function
and 170 meV in the band gap within a moiré unit cell, which
are comparable to h-BN/metallic interfaces. Additionally, we identify
dual moiré superlattices in twisted homobilayers of h-BN/Graphite,
offering an extra degree of freedom to tune the heterostructure’s
properties. These findings suggest that moiré engineering in
h-BN-based systems could lead to a range of effects, including exciton
broadening, twist-tunable defect luminescence, and the theoretically
predicted trapping of excitons within the moiré landscape.
Furthermore, this tunability may also affect adjacent layered materials,
providing a versatile platform for tailoring the electronic and optical
properties of h-BN and its van der Waals heterostructures.