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Effect of Film Thickness on the Far- and Near-Field Optical Response of Nanoparticle-on-Film Systems

preprint
submitted on 24.06.2019 and posted on 24.06.2019 by Rachel Armstrong, Willeke van Liempt, Peter Zijlstra

We study the near-field and far-field optical response of nanoparticle-on-film systems using single-nanoparticle spectroscopy and numerical simulations. We find that the optical spectra contain three dominant modes - a transverse dipole and quadrupole mode, and a dominant vertical antenna mode. We vary the thickness of the metal film from 10 – 45 nm, and find that the vertical antenna mode wavelength is nearly independent of the film thickness. In contrast, we find that the associated near-field enhancement in the gap between the particle and the film strongly depends on the film thickness. This trend is also observed in the far-field where the vertical antenna mode strongly increases in amplitude for increasing film-thicknesses up to the skin depth of gold. These findings are in good agreement with a numerical model and pave the way to study field-mediated processes such as fluorescence, SERS, and localized chemistry at the same resonance wavelength but at varying degrees of field enhancement.

History

Email Address of Submitting Author

p.zijlstra@tue.nl

Institution

Eindhoven University of Technology

Country

The Netherlands

ORCID For Submitting Author

0000-0001-9804-2265

Declaration of Conflict of Interest

no conflict of interest

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