Exciton mapping at subwavelength scales in two-dimensional materials

Abstract

Spatially resolved EELS has been performed at diffuse interfaces between MoS${}_2$ and MoSe${}_2$ single layers. With a monochromated electron source (20 meV) we have successfully probed excitons near the interface by obtaining the low loss spectra at the nanometer scale. The exciton maps clearly show variations even with a 10 nm separation between measurements; consequently the optical bandgap can be measured with nanometer-scale resolution, which is 50 times smaller than the wavelength of the emitted photons. By performing core-loss EELS at the same regions, we observe that variations in the excitonic signature follow the chemical composition. The exciton peaks are observed to be broader at interfaces and heterogeneous regions, possibly due to interface roughness and alloying effects. Moreover, we do not observe shifts of the exciton peak across the interface, possibly because the interface width is not much larger than the exciton Bohr radius.

References in corpus (4)

• Ultrafast Charge Transfer in Atomically Thin MoS2/WS2 Heterostructures
• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Giant Rydberg Excitons in Cuprous Oxide
• Nanometer Scale Spectral Imaging of Quantum Emitters in Nanowires and Its Correlation to Their Atomically Resolved Structure

Cited by in corpus (5)

• Lateral heterostructures and one-dimensional interfaces in 2D transition metal dichalcogenides
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• Deep analytics of atomically-resolved images: manifest and latent features
• Stationary waves in a superfluid gas of electron-hole pairs in bilayers
• Momentum Conserved Ultrafast Charge Transfer Dynamics of Interlayer Excitons in vdW Heterostructures