Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 82: Plasmonics and Nanooptics: Fabrication, Characterization and Applications II

O 82.5: Vortrag

Donnerstag, 20. März 2025, 11:30–11:45, H8

Nonlocal Substrate Influence on the Plasmon of a Supported Silver Nanoparticle — Kevin Oldenburg, Karl-Heinz Meiwes-Broer, and •Ingo Barke — ELMI-MV, Department Life, Light & Matter, and Institute of Physics, University of Rostock

The effect of a substrate on a particle plasmon (Localized Surface Plasmon Resonance, LSPR) is often considered to be of local nature, where the substrate primarily affects the plasmon at short distances [1]. Here we present spatially resolved plasmon excitation probabilities of a single 11 nm silver nanoparticle deposited from the gas phase onto a narrow rim of a carbon substrate ("cliffhanger"), thus providing a cross-sectional view. We employ electron energy loss spectroscopy (EELS) with a scanning transmission electron microscope (STEM) where we find the strongest substrate effect, i.e., the largest red shift, when the plasmon is excited farthest away. As will be discussed, this non-local substrate influence is a consequence of the simplicity and size of the system. These results are corroborated by simulations based on the boundary element method (BEM), which also help extract the full mode structure from the experimental data. Furthermore, we observe pronounced symmetry breaking, lifting the threefold degeneracy of the dominating dipole modes, potentially resolving long-standing discrepancies in the literature regarding plasmon energies of silver clusters in this size regime [2].
[1] S. Mazzucco, et al., Nano Letters 12, 1288 (2012).
[2] H. Haberland, Nature (2013), 494 E1-E2; A. Campos et al., Nature Physics (2019), 15, 275

Keywords: EELS; STEM; silver cluster; plasmon; nanoparticle