Well separated trion and neutral excitons on superacid treated MoS2 monolayers

Abstract

Developments in optoelectronics and spin-optronics based on transition metal dichalcogenide monolayers (MLs) need materials with efficient optical emission and well-defined transition energies. In as-exfoliated MoS2 MLs the photoluminescence (PL) spectra even at low temperature consists typically of broad, overlapping contributions from neutral, charged excitons (trions) and localized states. Here we show that in superacid treated MoS2 MLs the PL intensity increases by up to 60 times at room temperature. The neutral and charged exciton transitions are spectrally well separated in PL and reflectivity at T=4 K, with linewidth for the neutral exciton of 15 meV, but with similar intensities compared to the ones in as-exfoliated MLs at the same temperature. Time resolved experiments uncover picoseconds recombination dynamics analyzed separately for charged and neutral exciton emission. Using the chiral interband selection rules, we demonstrate optically induced valley polarization for both complexes and valley coherence for only the neutral exciton.

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Cited by in corpus (24)

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• Many-Body Theory of Trion Absorption Features in Two-Dimensional Semiconductors
• Brightening of dark excitons in monolayers of semiconducting transition metal dichalcogenides
• Control of Exciton Valley Coherence in Transition Metal Dichalcogenide Monolayers
• Direct exciton emission from atomically thin transition metal dichalcogenide heterostructures near the lifetime limit
• Optical response of monolayer, few-layer and bulk tungsten disulfide
• Exciton Trapping Is Responsible for the Long Apparent Lifetime in Acid-Treated MoS2
• Excitonic properties of semiconducting monolayer and bilayer MoTe2
• Electron-exciton interactions in the exciton-polaron problem
• Ultra-low power threshold for laser induced changes in optical properties of 2D Molybdenum dichalcogenides
• Opto-valleytronic imaging of atomically thin semiconductors
• Defect healing and charge transfer mediated valley polarization in MoS${}_2$/MoSe${}_2$/MoS${}_2$ trilayer van der Waals heterostructures
• Exciton-polarons in doped semiconductors in a strong magnetic field
• Mechanistic Insight to the Chemical Treatments of Monolayer Transition Metal Disulfides for Photoluminescence Enhancement
• Spectrally narrow exciton luminescence from monolayer MoS2 exfoliated onto epitaxially grown hexagonal BN
• Tuning carrier concentration in a superacid treated MoS${}_2$ monolayer
• Monolayer WS${}_2$ electro- and photo-luminescence enhancement by TFSI treatment
• The optical response of artificially twisted MoS${}_2$ bilayers
• Many-Body Effect of Mesoscopic Localized States in MoS${}_2$ Monolayer
• Spatiotemporal dynamics of free and bound excitons in CVD-grown MoS${}_2$ monolayer
• The Importance of Pure Dephasing in the Optical Response of Excitons in High-quality van der Waals Heterostructures
• Photoluminescence kinetics of dark and bright excitons in atomically thin MoS${}_2$
• Signatures of defect-localized charged excitons in the photoluminescence of monolayer molybdenum disulfide
• Localized Gradual Photomediated Brightness and Lifetime Increase of Superacid Treated Monolayer MoS${}_2$