Münster 1999 – scientific programme
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O: Oberflächenphysik
O 19: Elektronische Struktur (Experiment und Theorie) (II)
O 19.2: Talk
Tuesday, March 23, 1999, 16:30–16:45, S1
ELS-LEED study of collective electronic excitations on Ag thin films — •Francesca Moresco1, Mario Rocca1, Torsten Hildebrandt2, and Martin Henzler2 — 1INFM, Dipartimento di Fisica, via Dodecaneso 33, 16146 Genova, Italy — 2Institut fuer Festkoerperphysik, Universitaet Hannover, Appelstrasse 2, 30167 Hannover, Germany
Thin films of Ag deposited on Si(111) 7X7 have been studied by ELS-LEED. A combined energy-loss and SPA-LEED investigation has been performed, with the aim of correlating the behaviouir of collective electronic excitatons with the morphology of the film. We demonstrate that the plasmon energy on polycrystalline Ag overlayers is determined by the dimensions of the Ag grains and behaves like the Mie resonance of Ag clusters of the same size. By measuring the dispersion of such mode we prove that the plasmon remains confined inside the single grain, showing a dispersion only for wavelength smaller than the lateral dimension of the grain. The plasmon dispersion, measured for wavelengths lower than the grain size, is linear and positive, with a slope which increases with the grain dimensions.