Efficient cathodoluminescence of monolayer transitional metal dichalcogenides in a van der Waals heterostructure

Abstract

Monolayer two-dimensional transitional metal dichalcogenides, such as MoS2, WS2 and WSe2, are direct band gap semiconductors with large exciton binding energy. They attract growing attentions for opto-electronic applications including solar cells, photo-detectors, light-emitting diodes and photo-transistors, capacitive energy storage, photodynamic cancer therapy and sensing on flexible platforms. While light-induced luminescence has been widely studied, luminescence induced by injection of free electrons could promise another important applications of these new materials. However, cathodoluminescence is inefficient due to the low cross-section of the electron-hole creating process in the monolayers. Here for the first time we show that cathodoluminescence of monolayer chalcogenide semiconductors can be evidently observed in a van der Waals heterostructure when the monolayer semiconductor is sandwiched between layers of hexagonal boron nitride (hBN) with higher energy gap. The emission intensity shows a strong dependence on the thicknesses of surrounding layers and the enhancement factor is more than 1000 folds. Strain-induced exciton peak shift in the suspended heterostructure is also investigated by the cathodoluminescence spectroscopy. Our results demonstrate that MoS2, WS2 and WSe2 could be promising cathodoluminescent materials for applications in single-photon emitters, high-energy particle detectors, transmission electron microscope displays, surface-conduction electron-emitter and field emission display technologies.

arXiv comment13 pages, 5 figures

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• Interlayer Charge Transfer and Defect Creation in Type I van der Waals Heterostructures
• Direct Optical-Structure Correlation in Atomically Thin Dichalcogenides and Heterostructures
• Engineering 2D material exciton lineshape with graphene/h-BN encapsulation
• Cathodoluminescence spectroscopy of monolayer hexagonal boron nitride
• Nano-optics of transition metal dichalcogenides and their van der Waals heterostructures with electron spectroscopies
• Effect of electron-irradiation on layered quantum materials
• Quantum Confined Luminescence in Two dimensions
• Ballistic Dynamics of Flexural Thermal Movements in a Nano-membrane Revealed with Subatomic Resolution
• Double-superradiant cathodoluminescence
• Photonic Bound-States-in-the-Continuum Observed with an Electron Nanoprobe
• An atlas of photonic and plasmonic materials for cathodoluminescence microscopy
• Photoluminescence efficiency of MBE-grown MoSe${}_2$ monolayers featuring sharp excitonic lines and diverse grain structures
• Two-dimensional Ga${}_2$O${}_3$ glass: a large scale passivation and protection material for monolayer WS${}_2$