Dresden 2006 – scientific programme

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DS: Dünne Schichten

DS 1: Optical properties of thin films I

DS 1.4: Talk

Monday, March 27, 2006, 10:15–10:30, GER 37

Size and Surroundings Dependence of the Optical Interband Excitations in Silver Nanoparticles — •Uwe Kreibig and Almuth Hilger — I. Institute of Physics (IA) RWTH Aachen University D-52056 Aachen, Germany

Ag nanoparticles (2 nm mean diameter) were produced by our thermal evaporation cluster source THECLA. By expansion into UHV a free particle beam was created which could be embedded in different co-evaporated dielectric embedding media. The optical absorption was measured in the VIS-nearUV region, and, by Kramers-Kronig analysis, the average dielectric function of the particle material was determined. The susceptibility of the 4d-5sp interband transition edge could then be separated by subtracting the Drude-Sommerfeld contribution. Two essential results will be discussed: 1) The fine structure of the interband transition edge of the free nanoparticles differs markedly from bulk Ag. 2) The deviations from the bulk Ag spectrum depend clearly on the kind of embedding medium, applied. They are larger for LiF than for SiO₂ but both are smaller than for the free particles.