All-optical reversible manipulation of exciton and trion emissions in monolayer WS2

TL;DR

This paper demonstrates a reversible, all-optical method to tune the photoluminescence and exciton-trion states in monolayer WS2 using laser irradiation, enabling precise control for optoelectronic applications.

Contribution

It introduces a novel reversible all-optical technique to modulate PL and exciton-trion conversion in monolayer WS2 through laser-assisted gas molecule adsorption and desorption.

Findings

Reversible PL intensity modulation achieved.

Conversion between neutral exciton and trion demonstrated.

High spatial resolution control shown.

Abstract

Monolayer transition metal dichalcogenides (TMDs) are direct gap semiconductors emerging promising applications in diverse optoelectronic devices. To improve performance, recent investigations have been systematically focused on the tuning of their optical properties. However, an all-optical approach with the reversible feature is still a challenge. Here we demonstrate the tunability of the photoluminescence (PL) properties of monolayer WS2 via laser irradiation. The modulation of PL intensity, as well as the conversion between neutral exciton and charged trion have been readily and reversibly achieved by using different laser power densities. We attribute the reversible manipulation to the laser-assisted adsorption and desorption of gas molecules, which will deplete or release free electrons from the surface of WS2 and thus modify its PL properties. This all-optical manipulation, with advantages of reversibility, quantitative control, and high spatial resolution, suggests promising applications of TMDs monolayers in optoelectronic and nanophotonic applications, such as optical data storage, micropatterning, and display.