Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 29: Nanostructures at Surfaces III: Dots, Particles, and Clusters
O 29.3: Vortrag
Dienstag, 2. April 2019, 11:00–11:15, H25
Virtual Plasmonic Dimers of Silver Nanoparticles on Si(111)-(7x7) unraveled by Size-Correlated Single-Object Photoemission — •Kevin Oldenburg1, Hannes Hartmann1, Jean Lermé2, Karl-Heinz Meiwes-Broer1, Sylvia Speller1, and Ingo Barke1 — 1University of Rostock, Institute of Physics, 18059 Rostock, Germany — 2Université de Lyon, Institut Lumière Matière, 69622 Villeurbanne Cedex, France
Single object spectroscopy is capable of unravelling individual features of clusters at surfaces. Here we show that for highly polarizable substrates the frequently applied picture of an "effective" dielectric medium surrounding each particle falls short due to coupling of the particle plasmon with its image dipole [1,2]. Silver nanoparticles deposited on Si(111)-(7x7) are investigated by using PEEM, thus probing a large number of particles simultaneously. We show that even for sizes as small as 10 nm the dipole approximation breaks down, because the system inherently creates higher-order multipole modes [3]. Model calculations based on Generalized Mie theory [2] reveal that the formation of multipole modes is extremely sensitive to the local geometry on the scale of one Angström, expressed by the effective intra-dimer separation. On the one hand this leads to a fundamentally limited control over particle plasmon energies. On the other hand selective excitation enables tailored energy transfer into molecular aggregates by utilizing certain metal nanoparticles as nanoscopic light sources.
[1] Knight et al., Nano Letters 9, 2188 (2009) [2] Lermé et al., J. Phys. Chem. C 117, 6383 (2013) [3] Oldenburg et al., under review