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Proceedings Paper

Improved light emission and suppression of exciton exciton annihilation rate in monolayer tungsten disulfide by laser irradiation (Conference Presentation)
Author(s): Yongjun Lee; Ganesh Ghimire; Youngbum Kim; Changwon Seo; Jeongyong Kim
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Paper Abstract

The optical properties of monolayer transition-metal dichalcogenides (1L-TMDs) are predominantly governed by excitonic effects even in room temperature because of two-dimensional confined nature. As the result of strong coulomb interaction in 1L-TMDs, non-radiative exciton-exciton annihilation (EEA) is one of key influence to their light emission at nominal excitation density. Therefore, the modulation of EEA can help to make higher photoluminescence (PL) quantum yeild and develop optoelectric devices using 1L-TMDs. Here, we observed reduced EEA rate in mechanically exfoliated monolayer tungsten disulfide (1L-WS2) by laser irradiation with improved light emission at the saturating optical excitation level. PL efficiency of 1L-WS2 in irradiated region increased with increasing the excitation intensity and finally it was 3 times higher at high excitation level compared to that in non-irradiated region, while the laser irradiated regions in 1L-WS2 have lower PL intensity at low excitation level than non-irradiation region. This kind of the excitation density dependence was confirmed by time-resolved PL measurement and EEA rate was reduced about 3 times by laser irradiation. Sulfur vacancies and lattice distortion might be formed by laser irradiation which can give rise to lower PL and shorter lifetime in laser irradiated region of 1L-WS2. But, we attribute these laser induced defects or adsorption of oxygen molecules in air to the origin of reduced EEA by hindering exciton diffusion. Our results could provide an idea for high performance opto-electric devices.

Paper Details

Date Published: 18 September 2018
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Proc. SPIE 10731, Nanostructured Thin Films XI, 107310M (18 September 2018); doi: 10.1117/12.2320871
Show Author Affiliations
Yongjun Lee, Sungkyunkwan Univ. (Korea, Republic of)
Ganesh Ghimire, Sungkyunkwan Univ. (Korea, Republic of)
Youngbum Kim, Sungkyunkwan Univ. (Korea, Republic of)
Changwon Seo, Sungkyunkwan Univ. (Korea, Republic of)
Jeongyong Kim, Sungkyunkwan Univ. (Korea, Republic of)


Published in SPIE Proceedings Vol. 10731:
Nanostructured Thin Films XI
Akhlesh Lakhtakia; Tom G. Mackay, Editor(s)

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