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MM: Fachverband Metall- und Materialphysik
MM 6: Topical Session TEM II
MM 6.1: Topical Talk
Montag, 14. März 2011, 14:30–15:00, IFW A
Excitation of Surface Plasmon Resonances in Metallic Nanostructures — •Peter van Aken1, Wilfried Sigle1, Burcu Ögüt1, Nahid Talebi1,2, Christoph Koch1, and Ralf Vogelgesang3 — 1Stuttgart Center for Electron Microscopy, Stuttgart, Germany — 2Photonics Research Laboratory, University of Tehran, Iran — 3Max-Planck-Institute for Solid State Research, Stuttgart, Germany
In this contribution, the dielectric responses of metallic particles, like triangular Ag nanoprisms, of nanoholes and of rectangular slits in thin Ag films, drilled by using a focused ion beam, are studied by acquiring energy-filtering transmission electron microscopy (EFTEM) series on a 2k x 2k CCD camera using a 0.2 eV energy selecting slit for both the monochromator and the imaging energy filter with an acquisition time between 20 s and 30 s per image using the Zeiss SESAM microscope. We map surface plasmon resonances (SPRs) at optical wavelengths on single triangular silver nanoprisms, where extra multipolar SPRs on these nanoparticles could be detected. EFTEM images from the nanoholes in a thin Ag film were obtained at energy losses in the range from 0.6 eV to 2.8 eV. We observe localized SPRs as very pronounced intensity maxima visible in the image series. The length scale of some features is as small as 10-20 nm which can presently not be imaged by other besides electron microscopy techniques. We find two resonances that are typical for single, isolated holes. A comparison with calculations based on the discrete dipole approximation (DDSCAT) shows that these are dipolar and quadrupolar resonances.