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O: Fachverband Oberflächenphysik

O 36: Particles and clusters

O 36.6: Talk

Wednesday, March 25, 2009, 16:15–16:30, SCH A01

Optical properties of single alkali-earth particles on MgO films — •Philipp Myrach, Niklas Nilius, and Hans-Joachim Freund — Fritz-Haber-Institut der MPG, D14195 Berlin, Germany

Light emission spectroscopy with an STM is employed to study the optical properties of single Mg and Ca particles deposited on 8 ML thick MgO/Mo(001) films. The particles grow with distinct rectangular shapes due to the strong affinity of the alkali-earth atoms to the O ions in the oxide surface. The overall emission properties are governed by material-dependent plasmon excitations, giving rise to photon peaks at 2.3 and 2.1 eV for Mg and Ca particles, respectively. However, a characteristic fine-structure is superimposed on the optical response that originates from the plasmon excitation mechanism via inelastic electron transport in a double barrier STM junction. High excitation cross sections are observed at photon energies that correspond to the separation of quantized electron levels in the MgO conduction band, so called Gundlach resonances.