Ultra-Sensitive Extinction Measurements of Optically Active Defects in Monolayer MoS$_2$

TL;DR

This paper demonstrates a highly sensitive cavity-enhanced extinction spectroscopy method to detect and analyze optical defects in monolayer MoS$_2$, achieving detection limits below 0.01% extinction and revealing defect-related sub-gap absorption.

Contribution

The study introduces a novel hyperspectral imaging technique with ultra-sensitive detection capabilities for nanoscale defects in 2D materials.

Findings

Detection limit below 0.01% extinction

Identification of sulfur vacancy-bound excitons

Broad sub-gap absorption consistent with theory

Abstract

We utilize cavity-enhanced extinction spectroscopy to directly quantify the optical absorption of defects in MoS$_2$ generated by helium ion bombardment. We achieve hyperspectral imaging of specific defect patterns with a detection limit below 0.01% extinction, corresponding to a detectable defect density below $10^{11}$ cm$^{-2}$. The corresponding spectra reveal a broad sub-gap absorption, being consistent with theoretical predictions related to sulfur vacancy-bound excitons in MoS$_2$. Our results highlight cavity-enhanced extinction spectroscopy as efficient means for the detection of optical transitions in nanoscale thin films with weak absorption, applicable to a broad range of materials.