Room Temperature Micro-Photoluminescence Studies of Colloidal WS2 Nanosheets

Abstract

Wet-chemical syntheses for quasi two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising methods for straightforward solution-processing of these materials. However, photoluminescence properties of colloidal TMDs are virtually unexplored due to the typically non-emitting synthesis products. In this work, we demonstrate room temperature micro-photoluminescence of delicate ultrathin colloidal WS2 nanosheets synthesized from WCl6 and elemental sulfur in oleic acid and oleylamine at 320 °C for the first time. Both, mono- and multilayer photoluminescence are observed, revealing comparable characteristics to exfoliated TMD monolayers and underpinning the high quality of colloidal WS2 nanosheets. In addition, a promising long-term air-stability of colloidal WS2 nanosheets is found and the control of photodegradation of the structures under laser excitation is identified as a challenge for further advancing nanosheet monolayers. Our results render colloidal TMDs as easily synthesized and highly promising 2D semiconductors with optical properties fully competitive with conventionally fabricated ultrathin TMDs.

References in corpus (23)

• Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides
• Control of valley polarization in monolayer MoS2 by optical helicity
• Exciton Binding Energy and Nonhydrogenic Rydberg Series in Monolayer WS2
• Excitons in atomically thin transition metal dichalcogenides
• Evolution of Electronic Structure in Atomically Thin Sheets of WS2 and WSe2
• Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides
• Ultra-thin PbS sheets by two-dimensional oriented attachment
• Excitonic linewidth approaching the homogeneous limit in MoS2 based van der Waals heterostructures : accessing spin-valley dynamics
• Ultrafast Dynamics of Defect-Assisted Electron-Hole Recombination in Monolayer MoS2
• Large spin splitting in the conduction band of transition metal dichalcogenide monolayers
• Visibility of dichalcogenide nanolayers
• Electrical suppression of all nonradiative recombination pathways in monolayer semiconductors
• Identification of excitons, trions and biexcitons in single-layer WS2
• Why all the fuss about 2D semiconductors?
• Magneto-Optics of Exciton Rydberg States in a Monolayer Semiconductor
• Valley Polarization by Spin Injection in a Light-Emitting van der Waals Heterojunction
• Vertical CVD Growth of Highly Uniform Transition Metal Dichalcogenides
• Defect Tolerant Monolayer Transition Metal Dichalcogenides
• Optical spectroscopy of excited exciton states in MoS2 monolayers in van der Waals heterostructures
• Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition
• Guide to optical spectroscopy of layered semiconductors
• Spin coherence and dephasing of localized electrons in monolayer MoS${}_2$
• Exciton-to-trion conversion as a control mechanism for valley polarization in room-temperature monolayer WS${}_{\text{2}}$