Dresden 2020 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 50: Poster Session - Plasmonics and Nanooptics: Fabrication and Characterization
O 50.5: Poster
Dienstag, 17. März 2020, 18:15–20:00, P2/EG
Near-Field characterization of sponge-like gold structures using optical frequencies — •Nicolai Grund, Mike Prämassing, and Stefan Linden — Physikalisches Institut Universität Bonn, D-53115
Three-dimensional nanoporous gold films exhibit strong, plasmonic "hot spots" with resonance frequencies ranging from the visible to the infrared regime, depending on the average pore size. This feature distinguishes these samples as promising substrates for chemical sensing applications in a broad spectral range[1]. We present an experimental near-field study of nanoporous gold films showing resonances from the visible to the near-infrared wavelength regime. To fabricate the nanoporous gold films, we make use of the composition of commercially available leaf gold. It consists of Gold (Au) and Silver (Ag), where a large fraction of the Ag can be etched away using salpeter acid (HNO3). The average pore size can be controlled by choosing the initial ratio of Au and Ag. We utilize scattering-type scanning near-field optical microscopy (s-SNOM) in reflection mode in order to measure the near fields above the sample. The resulting two-dimensional near-field distributions allow to study the spatial distribution and density of plasmonic "hot-spots" on the film. Near-field imaging with different excitation wavelengths is used to determine the spectral occurrence and width of distinct hot spots.
[1] Wallace, Gregory Q., et al., Analyst 140.21 (2015): 7278-7282