Near-field imaging of exciton complexes of monolayer MoS2 with chemical treatment (Conference Presentation)

YoungBum Kim; Yongjun Lee; Shrawan Roy; Jeongyong Kim

doi:10.1117/12.2320875

17 September 2018 Near-field imaging of exciton complexes of monolayer MoS2 with chemical treatment (Conference Presentation)

YoungBum Kim, Yongjun Lee, Shrawan Roy, Jeongyong Kim

Author Affiliations +

Proceedings Volume 10726, Nanoimaging and Nanospectroscopy VI; 107260R (2018) https://doi.org/10.1117/12.2320875
Event: SPIE Nanoscience + Engineering, 2018, San Diego, California, United States

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDs) play important role for optoelectronic applications such as photovoltaics, photodetectors, and field-effect transistors (FETs). However, there are still limited by several problems such as structural defects during the chemical vapor deposition (CVD) growth process, poor photoluminescence (PL) quantum yield (QY) and deeply understanding of exciton dynamics of TMDs. Recently, it was reported that treatment using the superacid bis (trifluoromethane) sulfonamide (TFSI) resulted in a PL QY near 100% in exfoliated 1L-MoS2 monolayers. One of main reason of improved PL QY is due to repair defects induced sulfur vacancies. however, the effects of these chemical treatments varied greatly depending on the synthesis method and the type of 1L-TMD; therefore, the exact origin of the emission enhancement is still challenge. Here, we perform detailed optical characterization of TFSI and 7,7,8,8-tetracyanoquinodimethane (TCNQ) treaded with CVD-grown 1L-MoS2 by using near-field scanning optical imaging and spectroscopy with nanoscale spatial resolution (~80nm). NSOM is optical imaging technique beyond the diffraction limit using narrow aperture that has aperture size much less than the wavelength of light. We found that 1L-MoS2 of systematic variation of the spectral weights among neutral excitons, trions indicated that p-doping by TFSI treatment. However, the PL enhancement was attributed mainly to the reduction of structural defects caused by TFSI treatment. Our results suggest that 1L-MoS2 helps to clarify the mechanism by which chemical treatment enhances the optical properties of 1L-TMDs.

Conference Presentation

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YoungBum Kim, Yongjun Lee, Shrawan Roy, and Jeongyong Kim "Near-field imaging of exciton complexes of monolayer MoS2 with chemical treatment (Conference Presentation)", Proc. SPIE 10726, Nanoimaging and Nanospectroscopy VI, 107260R (17 September 2018); https://doi.org/10.1117/12.2320875

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KEYWORDS

Excitons

Near field

Chemical vapor deposition

Optical imaging

Field effect transistors

Optoelectronics

Photodetectors

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