Quantum Confined Luminescence in Two dimensions

TL;DR

This study demonstrates quantum confined luminescence in 2D monolayer TMD nanodots, revealing size-dependent emission properties and quantization effects, advancing potential applications in nanophotonics.

Contribution

First experimental observation of quantum confined luminescence in 2D TMD nanodots, showing size-dependent emission shifts and quantization effects.

Findings

Luminescence depends on nanodot size, with different excitons dominating at various sizes.

Quantum confinement effects cause a blue-shift in emission below 10 nm.

Localized light emission can be controlled by nanodot size in 2D TMDs.

Abstract

Achieving localized light emission from monolayer two-dimensional (2D) transition metal dichalcogenides (TMDs) embedded in the matrix of another TMD has been theoretically proposed but not experimentally proven. In this study, we used cathodoluminescence performed in a scanning transmission electron microscope to unambiguously resolve localized light emission from 2D monolayer MoSe2 nanodots of varying sizes embedded in monolayer WSe2 matrix. We observed that the light emission strongly depends on the nanodot size wherein the emission is dominated by MoSe2 excitons in dots larger than 85 nm, and by MoSe2/WSe2 interface excitons below 50 nm. Interestingly, at extremely small dot sizes (< 10 nm), the electron energy levels in the nanodot become quantized, as demonstrated by a striking blue-shift in interface exciton emission, thus inducing quantum confined luminescence. These results establish controllable light emission from spatially confined 2D nanodots, which holds potential to be generalized to other 2D systems towards future nanophotonic applications.