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Thermally-induced surface reconstruction of α-Al2O3 was used to fabricate corrugated templates of different periods to support percolated ultrathin metal film. Reflectance analysis and simulations revealed the coupling of a hybrid NIR-SPP mode along its corrugation vector (k_corrugation). The fabricated samples enhanced Raman signals of phenyl thiolates (PT) with reduced photo-induced disadvantages at λexc = 785 nm. Polarized SERS were performed to study adsorbed molecule–polariton interaction on these corrugated thin film surfaces. A twofold SERS anisotropy with a cos2(σ) dependency (σ = azimuthal angle) was observed. SERS dichroism of PT Raman modes of different polarizability tensors were analysed. A more pronounced dependence on corrugation period was observed for totally symmetric a1 modes than the non-totally symmetric b1 and b2 modes. Apart from the relative SERS intensity, their SERS dichroism was determined mostly by the excitation of SPP along the k_corrugation rather than the orientation of PT on sample surface. Edge-on orientation of adsorbed PT was predicted due to the absence of a2 modes with both tensor components parallel to the surface. Shorter corrugation periods fabricated were reproducible and ample for uniform, large-area sensing due to effective SPP coupling at σ = 0° resulting in a spatially extended SERS excitation volume.

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• Creative Commons BY Attribution 4.0 International
  

Keyword: NIR-surface plasmon polaritons, Long-range periodic nanostructure, Percolated ultrathin film plasmonics, Non-isotropic molecules on corrugated plasmonic surface, Polarized surface enhanced Raman spectroscopy, Dichroic SERS effect, Large area SERS sensing

Date published: 2024-03-02

Publisher: Elsevier BV

Journal:

• Applied Surface Science (ISSN: 01694332) vol. 659 159821

Funding:

• European Union Horizon 2020 research and innovation programme, grant 685451 (LaSensA project carried out under the M-ERA.NET 2 scheme )
• JSPS 20K05453 (Grant-in-Aid for Scientific Research(C))

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1016/j.apsusc.2024.159821

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Updated at: 2024-08-20 08:30:24 +0900

Published on MDR: 2024-08-20 08:30:25 +0900