Direct optical-structure correlation in atomically thin dichalcogenides and heterostructures
Name
1910.13387.pdf
Description
Submitted version
Size
2.42 MB
Format
Adobe PDF
Checksum (MD5)
1006f8d3daa7ec4e3df9ddb7fbe16332
Author(s)
Singh, Akshay k
Lee, Haeyeon
Gradečak, Silvija
Date Issued
January 2020
Journal
Nano Research
Publisher
Springer Science and Business Media LLC
Citation
Singh, Akshay, Hae Yeon Lee and Silvija Gradečak. “Direct optical-structure correlation in atomically thin dichalcogenides and heterostructures.” Nano Research, 13, 5 (January 2020): 1363–1368 © 2020 The Author(s)
Version
Original manuscript
Abstract
Atomically thin transition metal dichalcogenides (TMDs) have distinct opto-electronic properties including enhanced luminescence and high on-off current ratios, which can be further modulated by making more complex TMD heterostructures. However, resolution limits of conventional optical methods do not allow for direct nanoscale optical-structural correlation measurements in these materials, particularly of buried interfaces in TMD heterostructures. Here we use, for the first time, electron beam induced cathodoluminescence in a scanning transmission electron microscope (CL-STEM) to measure optical properties of monolayer TMDs (WS2, MoS2 and WSSe alloy) encapsulated between layers of hBN. We observe dark areas resulting from localized (~ 100 nm) imperfect interfaces and monolayer folding, which shows that the intimate contact between layers in this application-relevant heterostructure is required for proper inter layer coupling. We also realize a suitable imaging method that minimizes electron-beam induced changes and provides measurement of intrinsic properties. To overcome the limitation of small electron interaction volume in TMD monolayer (and hence low photon yield), we find that encapsulation of TMD monolayers with hBN and subsequent annealing is important. CL-STEM offers to be a powerful method to directly measure structure-optical correspondence in lateral or vertical heterostructures and alloys.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
Massachusetts Institute of Technology. Media Laboratory
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1007/S12274-019-2601-7
