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Owing to its anisotropic optical and electrical properties, rhenium diselenide (ReSe2) has garnered considerable attention recently as a candidate material for polarization-sensitive photodetectors. However, the direct and controllable synthesis of large-sized ReSe2 with a uniform thickness is still a great challenge. Herein, we have refined the synthesis method to obtain uniform monolayer ReSe2 flakes with a size of up to ~ 106 μm on sapphire via an ambient-pressure chemical vapor deposition technique using Na promoter from sodium chloride. Interestingly, optical pump-probe spectroscopy revealed a fast switching from saturable absorption (SA) to absorption enhancement (AE) in subpicosecond time scale, followed by a slower decay induced by exciton recombination. Furthermore, both AE and SA signals exhibited clear angular dependence with a periodicity of 180°, which reflected the dichroism in nonlinear absorption dynamics. In addition, the photocarrier dynamics including free-carrier transport and subpicosecond relaxation due to exciton formation or surface trapping was probed using time resolved terahertz spectroscopy. We believe that our study serves as a reference for atomically controlled synthesis of large-sized ReSe2 and provides useful insights on its optoelectronic properties for novel device applications.

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Publication history

Received: 05 November 2019
Revised: 14 January 2020
Accepted: 23 January 2020
Published: 12 February 2020
Issue date: March 2020

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© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020

Acknowledgements

The work was supported by the National Key Research and Development Program of China (Nos. 2018YFA0703700, 2017YFA0304600, and 2017YFA0205700), the National Natural Science Foundation of China (Nos. 51861135201, 21473001, 11774354, 11674329, and 51727806), Beijing Natural Science Foundation (No. 2192021), the Project funded by China Postdoctoral Science Foundation (No. 2018M640023), Chinese Academy of Science (No. YZJJ201705), Open Research Fund Program of the State Key Laboratory of Low-dimensional Quantum Physics (No. KF201907), and Start-up Funding of Peking University.

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Email: nanores@tup.tsinghua.edu.cn

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