# Exciton Manipulation via Dielectric Environment Engineering in 2D Semiconductors

## TL;DR

This paper explores how changing the dielectric environment affects the light emission of 2D semiconductors, offering insights for better optoelectronic devices.

## Contribution

The study systematically investigates the effects of dielectric screening, doping, and charge carrier concentration on 2D semiconductor light emission.

## Key findings

- p-type 1L-WSe2 shows higher PL intensity and red-shifted trion emission on HfO2.
- n-type 1L-WS2 exhibits blue-shifted, lower-intensity PL under similar dielectric conditions.
- Suspending monolayers enhances PL by reducing nonradiative recombination.

## Abstract

Two-dimensional (2D) semiconductors
are promising for
photonic
applications due to their exceptional optoelectronic properties, including
large exciton binding energy, strong spin–orbit coupling, and
potential integration with the standard complementary silicon-oxide-semiconductor
(CMOS) technology. The dielectric environment can significantly affect
the photoluminescence (PL) spectra of transition metal dichalcogenide
(TMD) monolayers by modulating excitonic properties such as optical
transitions and binding energies. Specifically, substrates with higher
dielectric permittivity reduce exciton binding energy and the quasiparticle
bandgap. Doping and the charge carrier concentration can further modify
the emitted spectra by affecting the PL excitonic content. Increased
doping can enhance trion formation and bandgap renormalization phenomena,
leading to PL spectral shifts that depend on the semiconductor type.
This study systematically investigates the substrate-induced dielectric
screening, doping, and trapped charges in CVD-grown n-type 1L-WS2 and p-type 1L-WSe2 transferred onto CMOS-relevant
SiO2 and HfO2 dielectrics. Our results show
that p-type 1L-WSe2 exhibits higher PL intensity and red-shifted
trion emission on HfO2, whereas n-type 1L-WS2 shows a blue-shifted, lower-intensity PL for a similar dielectric
environment. The difference arises from the interplay of the semiconductor
type, doping, dielectric screening, and charge carrier concentration.
We demonstrate that suspending the monolayers at the nanoscale enhances
PL by reducing nonradiative recombination, enabling controlled micro-PL
patterning and the formation of localized emission hot spots. Our
results provide valuable insights for the development of next-generation
CMOS-compatible optoelectronic devices.