# Nanoscale patterning of quasiparticle band alignment

## TL;DR

This study demonstrates nanoscale control of electronic band alignment in 2D heterostructures by utilizing patterned graphene on silicon carbide to tune adjacent WS$_2$ properties, enabling precise optoelectronic manipulation.

## Contribution

It introduces a method to achieve nanoscale patterning of quasiparticle band alignment in 2D materials using substrate-induced electrostatic gating.

## Key findings

- Band offsets in WS$_2$ track graphene work function.
- Lateral patterns of exciton and trion luminescence observed.
- Nanoscale control of optoelectronic properties demonstrated.

## Abstract

Control of atomic-scale interfaces between materials with distinct electronic structures is crucial for the design and fabrication of most electronic devices. In the case of two-dimensional (2D) materials, disparate electronic structures can be realized even within a single uniform sheet, merely by locally applying different vertical bias voltages. Indeed, it has been suggested that nanoscale electronic patterning in a single sheet can be achieved by placing the 2D material on a suitably pre-patterned substrate, exploiting the sensitivity of 2D materials to their environment via band alignment, screening or hybridization. Here, we utilize the inherently nano-structured single layer (SL) and bilayer (BL) graphene on silicon carbide to laterally tune the electrostatic gating of adjacent SL tungsten disulphide (WS$_2$) in a van der Waals heterostructure. The electronic band alignments are mapped in energy and momentum space using angle-resolved photoemission with a spatial resolution on the order of 500~nm (nanoARPES). We find that the SL WS$_2$ band offsets track the work function of the underlying SL and BL graphene, and we relate such changes to observed lateral patterns of exciton and trion luminescence from SL WS$_2$, demonstrating ultimate control of optoelectronic properties at the nanoscale.