Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 5: Plasmonics: Nanoantennas, Nanoparticles
O 5.6: Vortrag
Montag, 16. März 2015, 11:45–12:00, MA 042
The influence of porphyrin adsorption on the LSP resonances of individual silver clusters investigated with multi-photon photoemission electron microscopy — •Klaus Stallberg and Winfried Daum — Institut für Energieforschung und physikalische Technologien, TU Clausthal, Leibnizstraße 4, 38678 Clausthal-Zellerfeld
Photoemission electron microscopy (PEEM) in combination with short-pulse laser excitation is a valuable probe for the investigation of plasmonic excitations, as it allows for direct imaging of the electric field enhancement with a lateral resolution down to 50 nm. In this talk we adress the application of energy-resolved multi-photon PEEM for the investigation of localized surface plasmons (LSPs) of silver clusters in contact with zinc-tetraphenyl-porphyrin (ZnTPP) molecules. ZnTPP is a metal-organic dye with a strong absorption band at 422 nm, which is close to the LSP resonances of selected silver nanoparticles on Si(100). Recording PEEM images for incrementally increased laser wavelengths enables us to derive spatially resolved excitation spectra. We observe the electronic S0 → S2 Soret transition of porphyrin molecules as a strong resonance in the excitation spectra of thin porphyrin films. Similarly LSP resonances of individual silver clusters are obtained. Deposition of zinc-tetraphenyl-porphyrin (ZnTPP) molecules results in a shift of the LSP resonance towards shorter wavelengths while the porphyrins’ Soret resonance appears to be shifted to lower wavelengths indicating a coupling of the silver clusters’ LSP with the molecular Soret excitation.