Improved light emission and suppression of exciton exciton annihilation rate in monolayer tungsten disulfide by laser irradiation (Conference Presentation)

Yongjun Lee; Ganesh Ghimire; Youngbum Kim; Changwon Seo; Jeongyong Kim

doi:10.1117/12.2320871

18 September 2018 Improved light emission and suppression of exciton exciton annihilation rate in monolayer tungsten disulfide by laser irradiation (Conference Presentation)

Yongjun Lee, Ganesh Ghimire, Youngbum Kim, Changwon Seo, Jeongyong Kim

Author Affiliations +

Proceedings Volume 10731, Nanostructured Thin Films XI; 107310M (2018) https://doi.org/10.1117/12.2320871
Event: SPIE Nanoscience + Engineering, 2018, San Diego, California, United States

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.

Conference Presentation

Citation Download Citation

Yongjun Lee, Ganesh Ghimire, Youngbum Kim, Changwon Seo, and Jeongyong Kim "Improved light emission and suppression of exciton exciton annihilation rate in monolayer tungsten disulfide by laser irradiation (Conference Presentation)", Proc. SPIE 10731, Nanostructured Thin Films XI, 107310M (18 September 2018); https://doi.org/10.1117/12.2320871

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KEYWORDS

Excitons

Laser irradiation

Tungsten

Adsorption

Distortion

Luminescence

Modulation

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