Approaching the Intrinsic Photoluminescence Linewidth in Transition Metal Dichalcogenide Monolayers

TL;DR

This paper demonstrates fabrication techniques for high-quality TMDC monolayers with near-intrinsic photoluminescence linewidths, revealing fundamental excitonic properties by minimizing environmental inhomogeneity effects.

Contribution

It introduces encapsulation and substrate passivation methods that significantly reduce PL linewidth and spatial variation, approaching the intrinsic excitonic linewidth in TMDC monolayers.

Findings

PL linewidth as low as 1.7 meV achieved

Homogeneous linewidth of 1.43 meV determined

Inhomogeneous broadening reduced to 1.1 meV

Abstract

Excitonic states in monolayer transition metal dichalcogenides (TMDCs) have been the subject of extensive recent interest. Their intrinsic properties can, however, be obscured due to the influence of inhomogeneity in the external environment. Here we report methods for fabricating high quality TMDC monolayers with narrow photoluminescence (PL) linewidth approaching the intrinsic limit. We find that encapsulation in hexagonal boron nitride (h-BN) sharply reduces the PL linewidth, and that passivation of the oxide substrate by an alkyl monolayer further decreases the linewidth and also minimizes the charged exciton (trion) peak. The combination of these sample preparation methods results in much reduced spatial variation in the PL emission, with a full-width-at-half-maximum as low as 1.7 meV. Analysis of the PL line shape yields a homogeneous width of 1.43$\pm$0.08 meV and inhomogeneous broadening of 1.1$\pm$0.3 meV.