The effect of metallic substrates on the optical properties of monolayer MoSe$_{2}$

TL;DR

This study explores how different metallic substrates influence the optical properties of monolayer MoSe₂, revealing substrate-dependent changes in excitonic features and doping levels due to charge transfer at the interface.

Contribution

It demonstrates that metallic substrates can modulate the optical and electronic properties of MoSe₂ monolayers through charge transfer and Schottky barrier formation, offering a method to control 2D material behavior.

Findings

Metallic substrates cause distinctive optical spectra in MoSe₂ monolayers.

Substrate choice affects doping levels and excitonic features.

Charge transfer at the interface influences optical properties.

Abstract

Atomically thin materials, like semiconducting transition metal dichalcogenides (S-TMDs), are highly sensitive to the environment. This opens up an opportunity to externally control their properties by changing their surroundings. We investigate the effect of several metallic substrates on the optical properties of MoSe$_2$ monolayer (ML) deposited on top of them with photoluminescence and reflectance contrast techniques. The optical spectra of MoSe$_{2}$ MLs deposited on Pt, Au, Mo and Zr have distinctive metal-related lineshapes. In particular, a substantial variation in the intensity ratio and the energy separation between a negative trion and a neutral exciton is observed. It is shown that using metals as substrates affects the doping of S-TMD MLs. The explanation of the effect involves the Schottky barrier formation at the interface between the MoSe$_{2}$ ML and the metallic substrates. The alignment of energy levels at the metal/semiconductor junction allows for the transfer of charge carriers between them. We argue that a proper selection of metallic substrates can be a way to inject appropriate types of carriers into the respective bands of S-TMDs.