Substrate influence on transition metal dichalcogenide monolayer exciton absorption linewidth broadening

Abstract

The excitonic states of transition metal dichacolgenide (TMD) monolayers are heavily influenced by their external dielectric environment based on the substrate used. In this work, various wide bandgap dielectric materials, namely hexagonal boron nitride (\textit{h}-BN) and amorphous silicon nitride (Si${}_3$N${}_4$), under different configurations as support or encapsulation material for WS${}_2$ monolayers are investigated to disentangle the factors contributing to inhomogeneous broadening of exciton absorption lines in TMDs using electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). In addition, monolayer roughness in each configuration was determined from tilt series of electron diffraction patterns by assessing the broadening of diffraction spots by comparison with simulations. From our experiments, the main factors that play a role in linewidth broadening can be classified in increasing order of importance by: monolayer roughness, surface cleanliness, and substrate-induced charge trapping. Furthermore, because high-energy electrons are used as a probe, electron beam-induced damage on bare TMD monolayer is also revealed to be responsible for irreversible linewidth increases. \textit{h}-BN not only provides clean surfaces of TMD monolayer, and minimal charge disorder, but can also protect the TMD from irradiation damage. This work provides a better understanding of the mechanisms by which \textit{h}-BN remains, to date, the most compatible material for 2D material encapsulation, facilitating the realization of intrinsic material properties to their full potential.

References in corpus (14)

• Boron nitride substrates for high-quality graphene electronics
• The structure of suspended graphene sheets
• Valley polarization in MoS2 monolayers by optical pumping
• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Tightly bound excitons in monolayer WSe2
• Cross-sectional imaging of individual layers and buried interfaces of graphene-based heterostructures and superlattices
• Robust optical emission polarization in MoS2 monolayers through selective valley excitation
• Electron Beam Spectroscopy for Nanophotonics
• Exciton mapping at subwavelength scales in two-dimensional materials
• High-quality electrical transport using scalable CVD graphene
• Magnetooptics of layered two-dimensional semiconductors and heterostructures: progress and prospects
• Nanoscale modification of WS${}_2$ trion emission by its local electromagnetic environment
• Detection of graphene's divergent orbital diamagnetism at the Dirac point
• Plasmons in MoS2 Studied via Experimental and Theoretical Correlation of Energy Loss Spectra

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• Impacts of dielectric screening on the luminescence of monolayer WSe${}_2$
• Nanosecond nanothermometry in an electron microscope
• Engineering 2D material exciton lineshape with graphene/h-BN encapsulation
• Nano-optics of transition metal dichalcogenides and their van der Waals heterostructures with electron spectroscopies
• Electrically Controlled Interfacial Charge Transfer Induced Excitons in MoSe2-WSe2 Lateral Heterostructure
• Quantum Confined Luminescence in Two dimensions
• Optical properties of Fermi polarons in a GaInP/MoSe2 monolayer heterostructure