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O: Oberflächenphysik

O 28: Postersitzung (Elektronische Struktur, Grenzfläche fest-flüssig, Halbleiteroberflächen und -grenzflächen, Magnetismus und Symposium SYXM, Methodisches, Nanostrukturen, Oberflächenreaktionen, Teilchen und Cluster, Zeitaufgelöste Spektroskopie)

O 28.67: Poster

Mittwoch, 10. März 2004, 16:00–19:00, Bereich C

Homogeneous linewidth of gold nanoshells — •S. Brogl, G. Raschke, A. Susha, A. L. Rogach, T. A. Klar, and J. Feldmann — Photonics and Optoelectronics Group, Physics Department and CeNS, University of Munich, Amalienstr. 54, D-80799 Munich, Germany

Nanoshells composed of a few nanometer thin gold layer coated on Au₂S nanoparticles show a pronounced resonance in their scattering spectra for visible light. Similar to solid noble metal nanoparticles the origin of the resonance is a collective oscillation of the conduction band electrons, which is known as the nanoparticle plasmon (NPP). The NPP resonance position of a gold nanoshell can be tuned over a large spectral range by varying the relative size of the nanoparticle core and the thickness of the gold shell.

Experiments carried out on ensembles of nanoshells show a broad absorption linewidth (FWHM) of about 600 meV. This is by far exceeding what is expected by Mie-theory calculations which yield a NPP resonance line width of less than 100 meV. We investigate this discrepancy by measuring the homogeneous scattering spectrum of a single gold nanoshell using dark field microscopy. The results show a homogeneous linewidth narrowed by 50% compared to ensemble measurements. This indicates that inhomogeneities e.g. distribution of shell thicknesses and/or core diameters are one important parameter for line broadening.