Regensburg 2000 – wissenschaftliches Programm

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O: Oberflächenphysik

O 37: Teilchen und Cluster

O 37.3: Vortrag

Freitag, 31. März 2000, 11:45–12:00, H36

Photon Emission Spectroscopy of Individual Supported Metal Clusters — •Niklas Nilius¹, Norbert Ernst¹, Hans-Joachim Freund¹, and Peter Johansson² — ¹F.Haber-Institut, MPG, Berlin — ²Lund University, Sweden

To characterize the optical properties of individual supported metal clusters STM has been combined with optical spectroscopy. The arrangement allows the detection of the wavelength of photons emitted after electron injection from the tip. The method has been employed on Pt and Ag clusters grown on a thin Al2O3 film on NiAl(110). The photon emission from the NiAl(110) substrate is governed by two pronounced peaks in the red and near infrared region. Model calculations for the electromagnetic response of the tip-sample system allow an assignment of the emission to tip-induced plasmon resonances. Measurements on small Pt clusters supported on Al2O3/NiAl(110) revealed a damping and red shift these resonances but no new features in the spectra. For Ag clusters a strongly enhanced emission lines at 3.5-3.8eV appears. This could be explained by the decay of Mie-resonances inside the particle. The measurements showed that the energetic position, the width and the intensities of the emission lines depend on the cluster size.