期刊
NANOTECHNOLOGY
卷 29, 期 12, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1361-6528/aaa923
关键词
photoluminescence; WS2; WSe2; layer number identification; density functional theory; insulating substrates
资金
- Ministry of Science and Technology [2016YFA0200700, 2017YFA0205004]
- NSFC [21673054]
- Key Research Program of Frontier Science, CAS [QYZDB-SSW-SYS031]
- Open Project of Key Laboratory for UVemitting Materials
- Technology of Ministry of Education [130028725]
- NSFC for Excellent Young Scholars [51422201]
- Program of the NSFC [61505026, 21501167, 61604037, 61574031, 51732003, 51372035]
- '111' Project [B13013]
- Jilin Province [20160520009JH, 20160520115JH, 20160520114JH]
- Fundamental Research Funds for the Central Universities [2412017FZ010, 2412016KJ017]
Transition metal dichalcogenides (TMDs) with a typical layered structure are highly sensitive to their layer number in optical and electronic properties. Seeking a simple and effective method for layer number identification is very important to low-dimensional TMD samples. Herein, a rapid and accurate layer number identification of few-layer WS2 and WSe2 is proposed via locking their photoluminescence (PL) peak-positions. As the layer number of WS2/WSe2 increases, it is found that indirect transition emission is more thickness-sensitive than direct transition emission, and the PL peak-position differences between the indirect and direct transitions can be regarded as fingerprints to identify their layer number. Theoretical calculation confirms that the notable thickness-sensitivity of indirect transition derives from the variations of electron density of states of W atom d-orbitals and chalcogen atom p-orbitals. Besides, the PL peak-position differences between the indirect and direct transitions are almost independent of different insulating substrates. This work not only proposes a new method for layer number identification via PL studies, but also provides a valuable insight into the thickness-dependent optical and electronic properties of W-based TMDs.
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