Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 16: Surface State Spectroscopy II
O 16.1: Vortrag
Montag, 7. März 2016, 15:00–15:15, H4
Unoccupied band structure of MgO/Ag(100) — •Rebecca Pöschel, Gianluca di Filippo, Andrej Classen, and Thomas Fauster — Lehrstuhl für Festkörperphysik, Friedrich-Alexander Universtität Erlangen-Nürnberg, Staudtstraße 7, 91058 Erlangen, Germany
Magnesium oxide films were prepared by evaporating magnesium on a well-defined Ag(100) single crystal kept at 440 K in 5·10−7mbar oxygen. Films of different thicknesses between 1 ML to 20 ML were deposited on the crystal. The samples were studied by monochromatic angle-resolved two-photon photoelectron spectroscopy (photon energies 3.05 eV - 3.38 eV and 4.56 eV - 4.71 eV) and by angle-resolved vacuum ultra-violet photoelectron spectroscopy (photon energy 21.2 eV). Due to the negative electron affinity of MgO the conduction band minimum is observed near the low-energy cut-off and the valence band maximum near the high-energy cut-off within same UPS spectrum. We determined the evolution of the band gap with increasing film thickness and had a more detailed look at the dispersion of the conduction band minimum and the valence band maximum for a 5 ML and 20 ML thick film. For films up to 10 ML we found an unoccupied surface state with a binding energy of 1.24 eV relative to vacuum level which shows a free-electron-like dispersion.