Hundredfold Enhancement of Light Emission via Defect Control in Monolayer Transition-Metal Dichalcogenides

TL;DR

This study demonstrates that controlling intrinsic point defects in monolayer transition-metal dichalcogenides significantly enhances light emission efficiency, achieving a hundredfold increase by reducing defect density through optimized synthesis.

Contribution

The paper identifies the main intrinsic defects in TMD monolayers and shows how synthetic condition control drastically reduces defect density and boosts radiative recombination efficiency.

Findings

Defects are mainly metal vacancies and chalcogen antisites.

Defect density can be reduced from above 10^13/cm^2 to below 10^11/cm^2.

Light emission efficiency increases by a factor of 100.

Abstract

Two dimensional (2D) transition-metal dichalcogenide (TMD) based semiconductors have generated intense recent interest due to their novel optical and electronic properties, and potential for applications. In this work, we characterize the atomic and electronic nature of intrinsic point defects found in single crystals of these materials synthesized by two different methods - chemical vapor transport and self-flux growth. Using a combination of scanning tunneling microscopy (STM) and scanning transmission electron microscopy (STEM), we show that the two major intrinsic defects in these materials are metal vacancies and chalcogen antisites. We show that by control of the synthetic conditions, we can reduce the defect concentration from above $10^{13} /cm^2$ to below $10^{11} /cm^2$. Because these point defects act as centers for non-radiative recombination of excitons, this improvement in material quality leads to a hundred-fold increase in the radiative recombination efficiency.