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Determining the Optimized Interlayer Separation Distance in Vertical Stacked 2D WS 2 :hBN:MoS 2 Heterostructures for Exciton Energy Transfer
Author(s) -
Xu Wenshuo,
Kozawa Daichi,
Liu Yu,
Sheng Yuewen,
Wei Ke,
Koman Volodymyr B.,
Wang Shanshan,
Wang Xiaochen,
Jiang Tian,
Strano Michael S.,
Warner Jamie H.
Publication year - 2018
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201703727
Subject(s) - heterojunction , materials science , femtosecond , photoluminescence , exciton , monolayer , semiconductor , quenching (fluorescence) , optoelectronics , chemical vapor deposition , trion , ultrafast laser spectroscopy , spectroscopy , analytical chemistry (journal) , laser , nanotechnology , condensed matter physics , optics , chemistry , fluorescence , physics , chromatography , quantum mechanics
The 2D semiconductor monolayer transition metal dichalcogenides, WS 2 and MoS 2 , are grown by chemical vapor deposition (CVD) and assembled by sequential transfer into vertical layered heterostructures (VLHs). Insulating hBN, also produced by CVD, is utilized to control the separation between WS 2 and MoS 2 by adjusting the layer number, leading to fine‐scale tuning of the interlayer interactions within the VLHs. The interlayer interactions are studied by photoluminescence (PL) spectroscopy and are demonstrated to be highly sensitive to the input excitation power. For thin hBN separators (one to two layers), the total PL emission switches from quenching to enhancement by increasing the laser power. Femtosecond broadband transient absorption measurements demonstrate that the increase in PL quantum yield results from Förster energy transfer from MoS 2 to WS 2 . The PL signal is further enhanced at cryogenic temperatures due to the suppressed nonradiative decay channels. It is shown that (4 ± 1) layers of hBN are optimum for obtaining PL enhancement in the VLHs. Increasing thickness beyond this causes the enhancement factor to diminish, with the WS 2 and MoS 2 then behaving as isolated noninteracting monolayers. These results indicate how controlling the exciton generation rate influences energy transfer and plays an important role in the properties of VLHs.