1. Inhomogeneous defect distribution of triangular WS2 monolayer revealed by surface-enhanced and tip-enhanced Raman and photoluminescence spectroscopy.
- Author
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Miao, Peng, Chen, Yu-Ting, Pan, Lin, Horneber, Anke, Greulich, Katharina, Chassé, Thomas, Peisert, Heiko, Adam, Pierre-Michel, Xu, Ping, Meixner, Alfred, and Zhang, Dai
- Subjects
COPPER surfaces ,RAMAN spectroscopy ,OPTICAL measurements ,MICROSCOPY ,MONOMOLECULAR films ,SERS spectroscopy ,SPATIAL resolution - Abstract
Confocal optical microscopy and tip-enhanced optical microscopy are applied to characterize the defect distributions in chemical vapor deposition-grown WS
2 monolayer triangles qualitatively and quantitatively. The presence of defects in individual monolayer WS2 triangles is revealed with diffraction-limited spatial resolution in their photoluminescence (PL) images, from which the inhomogeneous defect density distribution is calculated, showing an inverse relationship to the PL intensity. The defect-related surface-enhanced Raman spectroscopy (SERS) effect is investigated by depositing a thin copper phthalocyanine layer (5 nm) as the probe molecule on the monolayer WS2 triangles surface. Higher SERS enhancement effects are observed at the defect-rich areas. Furthermore, tip-enhanced optical measurements are performed, which can reveal morphologically defected areas invisible in the confocal optical measurements. Furthermore, the area with high defect density appears brighter than the low-defected area in the tip-enhanced optical measurements, which are different from the observation in the confocal optical measurements. The underlying reasons are attributed to the near-field enhancement of the defect exciton emission induced by the optically excited tip and to an improved coupling efficiency between the tip-generated near-field with the altered dipole moment orientation at the local defect. [ABSTRACT FROM AUTHOR]- Published
- 2022
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