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Published January 12, 2024 | Published
Journal Article Open

Dramatically Enhanced Valley-Polarized Emission by Alloying and Electrical Tuning of Monolayer WTe₂ₓS₂₍₁₋ₓ₎ Alloys at Room Temperature with 1T′-WTe₂-Contact


Monolayer ternary tellurides based on alloying different transition metal dichalcogenides (TMDs) can result in new two‐dimensional (2D) materials ranging from semiconductors to metals and superconductors with tunable optical and electrical properties. Semiconducting WTe2xS2(1‐x) monolayer possesses two inequivalent valleys in the Brillouin zone, each valley coupling selectively with circularly polarized light (CPL). The degree of valley polarization (DVP) under the excitation of CPL represents the purity of valley polarized photoluminescence (PL), a critical parameter for opto‐valleytronic applications. Here, new strategies to efficiently tailor the valley‐polarized PL from semiconducting monolayer WTe2xS2(1‐x) at room temperature (RT) through alloying and back‐gating are presented. The DVP at RT is found to increase drastically from < 5% in WS2 to 40% in WTe0.12S1.88 by Te‐alloying to enhance the spin‐orbit coupling. Further enhancement and control of the DVP from 40% up to 75% is demonstrated by electrostatically doping the monolayer WTe0.12S1.88 via metallic 1T′‐WTe2 electrodes, where the use of 1T′‐WTe2 substantially lowers the Schottky barrier height (SBH) and weakens the Fermi‐level pinning of the electrical contacts. The demonstration of drastically enhanced DVP and electrical tunability in the valley‐polarized emission from 1T′‐WTe2/WTe0.12S1.88 heterostructures paves new pathways towards harnessing valley excitons in ultrathin valleytronic devices for RT applications.

Copyright and License

© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.


This work was jointly supported by the Army Research Office under the Multi-University Research Initiative (MURI) program (award #W911NF-16-1-0472) and the National Science Foundation under the Physics Frontier Center program for Institute for Quantum Information and Matter (IQIM) at the California Institute of Technology (award #1733907). The authors also acknowledged support from the Beckman Institute at the California Institute of Technology for access to facilities at the Molecular Materials Research Center. W.-H. Lin thanks Ruohan Wang for great discussion and support and acknowledged a graduate fellowship from the J. Yang Family Foundation. C.-S. Li acknowledges the support from the Ministry of Science and Technology in Taiwan (award #108-2911-I-002-524 and 109-2622-8-002-003) for his visit and research at Caltech.


W.-H.L. and N.-C.Y. conceived the research ideas. W.-H.L. and C.-S.L. contributed equally to this work. W.-H.L. constructed the CVD system for WS₂, WTe₂, and WTe₂ₓS₂₍₁₋ₓ₎ growth and participated in all the measurements and data analysis. W.-H.L. and H.A.A. contributed to the XPS measurement. W.-H.L., C.-S.L., and G.R.R. contributed to the Raman and PL mapping measurements. W.-H.L., C.-S.L., and C.I.W. contributed to the FET device measurements. W.-H.L. and N.-C.Y. wrote the manuscript, and N.-C.Y. supervised and coordinated the project.

Conflict of Interest

The authors declare no conflict of interest.

Data Availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.


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January 17, 2024
January 18, 2024