Exciton Confinement in Two-Dimensional, In-Plane, Quantum Heterostructures

TL;DR

This paper demonstrates the creation and optical characterization of in-plane MoSe2 quantum dots within WSe2 monolayers, revealing size-dependent exciton confinement and single-photon emission, advancing 2D quantum light source development.

Contribution

It reports a novel epitaxial growth method for lateral MoSe2 quantum dots with tunable optical properties and single-photon emission capabilities.

Findings

Size-dependent exciton blue shift observed (12-40 meV)

Lateral quantum dots exhibit single-photon emission at 1.6 K

Epitaxial growth enables controlled in-plane quantum confinement

Abstract

Two-dimensional (2D) semiconductors are promising candidates for optoelectronic application and quantum information processes due to their inherent out-of-plane 2D confinement. In addition, they offer the possibility of achieving low-dimensional in-plane exciton confinement, similar to zero-dimensional quantum dots, with intriguing optical and electronic properties via strain or composition engineering. However, realizing such laterally confined 2D monolayers and systematically controlling size-dependent optical properties remain significant challenges. Here, we report the observation of lateral confinement of excitons in epitaxially grown in-plane MoSe2 quantum dots (~15-60 nm wide) inside a continuous matrix of WSe2 monolayer film via a sequential epitaxial growth process. Various optical spectroscopy techniques reveal the size-dependent exciton confinement in the MoSe2 monolayer quantum dots with exciton blue shift (12-40 meV) at a low temperature as compared to continuous monolayer MoSe2. Finally, single-photon emission was also observed from the smallest dots at 1.6 K. Our study opens the door to compositionally engineered, tunable, in-plane quantum light sources in 2D semiconductors.