# Engineering of Neutral Excitons and Exciton Complexes in Transition Metal Dichalcogenide Monolayers through External Dielectric Screening

## TL;DR

This paper demonstrates how dielectric environments can be used to precisely tune excitonic properties in transition metal dichalcogenide monolayers, enabling the creation of atomically sharp heterojunctions for advanced electronic applications.

## Contribution

It provides a detailed analysis of dielectric screening effects on excitonic transitions in TMD monolayers, introducing a non-invasive method to engineer heterojunctions.

## Key findings

- Achieved up to 37 meV tuning of optical band gaps.
- Observed around 30% change in exciton binding energies.
- Reduced the electronic band gap of WSe2 monolayers by 120 meV.

## Abstract

In order to fully exploit the potential of transition metal dichalcogenide monolayers (TMD-MLs), the well-controlled creation of atomically sharp lateral heterojunctions within these materials is highly desirable. A promising approach to create such heterojunctions is the local modulation of the electronic structure of an intrinsic TMD-ML via dielectric screening induced by its surrounding materials. For the realization of this non-invasive approach, an in-depth understanding of such dielectric effects is required. We report on the modulations of excitonic transitions in TMD-MLs through the effect of dielectric environments including low-k and high-k dielectric materials. We present absolute tuning ranges as large as 37 meV for the optical band gaps of WSe 2 and MoSe 2 MLs and relative tuning ranges on the order of 30% for the binding energies of neutral excitons in WSe 2 MLs. The findings suggest the possibility to reduce the electronic band gap of WSe 2 MLs by 120 meV, paving the way towards dielectrically defined lateral heterojunctions.