Atomistic defect states as quantum emitters in monolayer MoS$_2$

TL;DR

This paper demonstrates a method to create and control defect states in monolayer MoS₂ using focused helium ion beams, enabling spectrally narrow quantum light emission for potential quantum device applications.

Contribution

It introduces a deterministic defect engineering technique in monolayer MoS₂ via helium ion irradiation, facilitating controlled quantum light sources.

Findings

Defects produce narrow emission lines below the neutral exciton energy.

Emission attributed to localized electron-hole complexes at defect sites.

Technique enables potential for scalable quantum photonic systems.

Abstract

Quantum light sources in solid-state systems are of major interest as a basic ingredient for integrated quantum device technologies. The ability to tailor quantum emission through deterministic defect engineering is of growing importance for realizing scalable quantum architectures. However, a major difficulty is that defects need to be positioned site-selectively within the solid. Here, we overcome this challenge by controllably irradiating single-layer MoS$_{2}$ using a sub-nm focused helium ion beam to deterministically create defects. Subsequent encapsulation of the ion bombarded MoS$_{2}$ flake with high-quality hBN reveals spectrally narrow emission lines that produce photons at optical wavelengths in an energy window of one to two hundred meV below the neutral 2D exciton of MoS$_{2}$. Based on ab-initio calculations we interpret these emission lines as stemming from the recombination of highly localized electron-hole complexes at defect states generated by the helium ion bombardment. Our approach to deterministically write optically active defect states in a single transition metal dichalcogenide layer provides a platform for realizing exotic many-body systems, including coupled single-photon sources and exotic Hubbard systems.