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Revealing local structural properties of an atomically thin MoSe2 surface using optical microscopy.
Lin Pan1,2,3, Peng Miao1,3, Anke Horneber1,3
1Institute of Physical and Theoretical Chemistry, Eberhard Karls University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany.
Beilstein Journal of Nanotechnology
|July 21, 2022
Summary
The study shows laser polarization significantly affects Raman enhancement on molybdenum diselenide (MoSe2) surfaces. Local structure also correlates with optical properties, impacting surface-enhanced Raman spectroscopy (SERS) performance.
Area of Science:
- Materials Science
- Spectroscopy
- Nanotechnology
Background:
- Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for molecular detection.
- Two-dimensional materials like molybdenum diselenide (MoSe2) offer unique optical and electronic properties for SERS.
- Understanding the influence of material structure and excitation conditions is crucial for optimizing SERS performance.
Purpose of the Study:
- To investigate the impact of laser polarization and local structure on SERS enhancement using MoSe2.
- To correlate structural irregularities of MoSe2 flakes with their optical properties and SERS response.
- To elucidate the interaction mechanisms between probe molecules and the MoSe2 substrate.
Main Methods:
- Utilized a triangular MoSe2 flake as a SERS platform.
- Employed copper phthalocyanine (CuPc) as the probe molecule.
- Used second harmonic generation (SHG) and photoluminescence (PL) spectroscopy and microscopy to characterize MoSe2 structure and optical properties.
- Investigated SERS enhancement under different laser beam polarizations (azimuthal and radial).
Main Results:
- Raman enhancement was significantly stronger with an azimuthally polarized beam (in-plane electric field) compared to a radially polarized beam (out-of-plane electric field).
- SHG and PL imaging revealed structural irregularities in the MoSe2 flake.
- SERS signal intensity mapped onto the MoSe2 surface showed a strong correlation with SHG and PL images, highlighting the influence of local structure.
- Observed strong interactions (charge transfer, dipole-dipole) between face-on oriented CuPc molecules and the MoSe2 surface.
Conclusions:
- Laser beam polarization critically influences SERS enhancement on MoSe2 substrates.
- Local structural features and optical properties of 2D materials directly impact SERS efficiency.
- This work provides insights into optimizing SERS platforms based on transition-metal dichalcogenides by controlling substrate morphology and excitation polarization.
