Exciton tuning in monolayer WSe$_2$ via substrate induced electron doping

TL;DR

This study demonstrates how substrate-induced electron doping in monolayer WSe$_2$ can significantly tune excitonic properties, offering a simple method for exciton control relevant for device applications.

Contribution

It reveals substrate-induced electron doping as a means to tune excitonic features in monolayer WSe$_2$, supported by systematic PL and KPFM measurements.

Findings

Redshift of ~62 meV in A exciton with HOPG substrate

Significant PL quenching and increased trion emission

Electron doping from substrate causes excitonic behavior change

Abstract

We report on large exciton tuning in WSe$_2$ monolayers via substrate induced non-degenerate doping. We observe a redshift of $\sim$62 meV for the $A$ exciton together with a 1-2 orders of magnitude photoluminescence (PL) quenching when the monolayer WSe$_2$ is brought in contact with highly oriented pyrolytic graphite (HOPG) compared to the dielectric substrates such as hBN and SiO$_2$. As the evidence of doping from HOPG to WSe$_2$, a drastic increase of the trion emission intensity was observed. Using a systematic PL and Kelvin probe force microscopy (KPFM) investigation on WSe$_2$/HOPG, WSe$_2$/hBN, and WSe$_2$/graphene, we conclude that this unique excitonic behavior is induced by electron doping from the substrate. Our results propose a simple yet efficient way for exciton tuning in monolayer WSe$_2$, which plays a central role in the fundamental understanding and further device development.