# Imaging microscopic electronic contrasts at the interface of single-layer WS$_2$ with oxide and boron nitride substrates

## TL;DR

This study employs photoemission electron microscopy to analyze the microscopic electronic contrasts at the interfaces of single-layer WS$_2$ with various substrates, revealing insights into band alignment crucial for device engineering.

## Contribution

It introduces a microscopy-based approach to directly image and analyze the electronic structures at WS$_2$ interfaces with different substrates, advancing understanding of substrate effects on 2D materials.

## Key findings

- Identified microscopic regions with clean interfaces using work function and X-ray imaging.
- Measured valence band offsets to determine band alignments.
- Discussed implications for vertical band structure engineering.

## Abstract

The electronic properties of devices based on two-dimensional materials are significantly influenced by interactions with substrate and electrode materials. Here, we use photoemission electron microscopy to investigate the real- and momentum-space electronic structures of electrically contacted single-layer WS$_2$ stacked on hBN, SiO$_2$ and TiO$_2$ substrates. Using work function and X-ray absorption imaging we single-out clean microscopic regions of each interface type and collect the valence band dispersion. We infer the alignments of the electronic band gaps and electron affinities from the measured valence band offsets of WS$_2$ and the three substrate materials using a simple electron affinity rule and discuss the implications for vertical band structure engineering using mixed three- and two-dimensional materials.