Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 41: Poster Session I (Semiconductor Substrates: Epitaxy and growth; Semiconductor Substrates: Adsorbtion; Semiconductor Substrates: Solid-liquid interfaces; Semiconductor Substrates: Clean surfaces; Oxides and insulators: Epitaxy and growth; Oxides and insulators: Adsorption; Oxides and insulators: Clean surfaces; Organic, polymeric and biomolecular films - also with adsorbates; Organic electronics and photovoltaics, Surface chemical reactions; Heterogeneous catalysis; Phase transitions; Particles and clusters; Surface dynamics; Surface or interface magnetism; Electron and spin dynamics; Spin-Orbit Interaction at Surfaces; Electronic structure; Nanotribology; Solid/liquid interfaces; Graphene; Others)
O 41.85: Poster
Dienstag, 23. März 2010, 18:30–21:00, Poster B1
Momentum microscope mapping of electronic states at Cu(111) surfaces by two- and three-photon photoemission — •Ahmet Akin Ünal, Christian Tusche, Cheng-Tien Chiang, Aimo Winkelmann, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
We investigate occupied and unoccupied electronic states of Cu(111) using multi-photon photoemission experiments. The frequency-doubled linear-polarized output of a Ti:sapphire oscillator with photon energy of hν = 3.1 eV is used as the excitation source. The electronic dispersions of the unoccupied Shockley surface state and n = 1 image potential state of Cu(111) are obtained by two- and three-photon photoemission using a momentum microscope, which comprises a photoelectron emission microscope (PEEM) in combination with two hemispherical imaging energy analyzers. In the case of three-photon photoemission, a one-photon resonance between the unoccupied surface and image-potential states is observed at k∥ ≈ ±0.66 Å−1. We also investigate the space-charge effects in the momentum microscope as a function of laser intensity and electron optical conditions in the instrument. As a measure of the space-charge effects, the broadening in the energy and momentum distributions of the observed electronic transitions is analyzed.