Berlin 2005 – scientific programme
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O: Oberflächenphysik
O 12: Nanostrukturen I
O 12.3: Talk
Friday, March 4, 2005, 16:15–16:30, TU EB202
Collective Surface Plasmon Modes in Ensembles of Gold Particles — •Phillip Olk1, Jan Seidel1, Stefan Grafström1, Lukas Eng1, Marcell Ott2, and Martin Möller2 — 1Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden — 2Dt. Wollforschungsinstitut an der RWTH Aachen, 52062 Aachen
The optical properties of self-arranged spherical gold nanoparticles are studied by means of scanning near-field optical microscopy (SNOM) and white-light spectroscopy. Films were prepared by plasma etching of self-arranged monolayers of inverted micelles which were loaded with gold salt[1]. Continuous decoration of both glass and silicon substrates is possible, resulting in typical inter-particle distances of 120 nm and sphere diameters of 10 nm.
When exciting the cluster array in a Kretschmann-Raether-like total-internal-reflection set-up, we find surface-bound optical modes very similar to surface plasmon polaritons on flat continuous metal films. We detect such modes by scanning a dielectric SNOM tip across the surface and recording the amount of evanescent light above the sample surface.
Although our films are far from being continuous metal films, the modes are found to decay in intensity with a decay length measuring > 20 µm, comparable to the decay length of surface plasmon polaritons in dense metal films. Moreover, the decay length is found to depend on wavelength and in-plane k component, indicating the existence of a material-dependent optical band structure.
[1] J. P. Spatz et al., Langmuir 16, 407–415 (2000)