Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 23: Symposium: Ultrafast Nanooptics III
O 23.6: Vortrag
Dienstag, 27. März 2007, 12:30–12:45, H38
Dephasing time and damping mechanisms of surface plasmon polaritons in gold nanoparticles — •Nils Borg, David Blazquez Sanchez, Christian Hendrich, Frank Hubenthal, and Frank Träger — Institut für Physik und Center for Interdisciplinary Nanostructure Science and Technology - CINSaT, Universität Kassel, Heinrich-Plett-Straße 40, D-34132 Kassel
The ultrafast electron dynamics in gold nanoparticles (NPs) was studied by measuring the dephasing time T2 of the surface plasmon polariton by means of persistent spectral hole burning. The dephasing time of gold grown on sapphire and TiO2 substrates was measured as a function of photon energy and the particle size. Dephasing times ranging from 5 to 17 fs were extracted. Furthermore, an explicit influence of the reduced dimension of the NPs has been determind, which plays a role for NPs with radii below 12 nm already. Most importantly, a dependence of T2 on the decreasing particle dimensions which fulfilled a 1/R-dependence was found and we could obtain a damping parameter for gold on sapphire of A = (0.32 ± 0.06) nm/fs. Comparison with other measurements as well as with theoretical predictions could identify surface scattering and Landau-damping as the most important mechanisms. Recent further experiments on gold NPs supported on TiO2 showed a further reduction of the dephasing time. For example, for NPs with a radius of approximately 13 nm we observed a decrease from T2 ≈ 15 fs for NPs grown on sapphire to T2 ≈ 12 fs for NPs grown on TiO2 at a photon energy of 1.65 eV. This indicates an additional damping mechanism, i.e. chemical interface damping.