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All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics
Published on: January 19, 2018
Imaging Valley Excitons in a 2D Semiconductor with Scanning Tunneling Microscope-Induced Luminescence
Hairui Geng1, Jie Tang1, Yanwei Wu1
1Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Optoelectronic Information Acquisition and Manipulation, Ministry of Education, School of Physics and Optoelectronics Engineering, Anhui University, Hefei Anhui 230601, China.
Researchers imaged valley excitons in 2D materials using scanning tunneling microscopy-induced luminescence. This technique reveals nanoscale variations in excitonic states, crucial for controlling optoelectronic properties.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Valley excitons are key to the optoelectronic properties of transition-metal dichalcogenides.
- Understanding nanoscale variations in excitonic states is essential for controlling material properties.
- Atomic-scale correlation between excitonic behavior and crystal structure is needed.
Purpose of the Study:
- To image valley excitons in a 2D semiconductor monolayer with atomic-scale resolution.
- To correlate excitonic states with localized structural and environmental inhomogeneities.
- To explore a novel platform for tailoring optoelectronic processes in 2D materials.
Main Methods:
- Utilized scanning tunneling microscope-induced luminescence (STML) microscopy.
- Fabricated a lateral homojunction of a 2D semiconductor monolayer on hexagonal boron nitride (hBN) and an Au electrode.
- Applied ambipolar voltages to observe chiral excitonic emission.
Main Results:
- Achieved subnanometer resolution imaging of valley excitons, revealing spatial variations linked to impurities and disorders.
- Observed chiral excitonic emission from neutral and charged valley excitons with quantum efficiency up to ~10^-5 photon/electron.
- Demonstrated voltage-dependent circular polarization of emitted light, reaching up to 40%.
Conclusions:
- STML microscopy provides a powerful tool for atomic-scale investigation of excitonic phenomena in 2D materials.
- Localized inhomogeneities significantly impact valley exciton behavior and optoelectronic response.
- The developed platform offers new avenues for precise control and tailoring of 2D material optoelectronics.
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