Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 86: Ultrafast Surface Dynamics I
O 86.6: Talk
Thursday, March 10, 2016, 16:15–16:30, S052
Two-Photon Photoemission on ultrathin CoO films — •Mathias Albrecht1, Konrad Gillmeister1, Cheng-Tien Chiang2,1, and Wolf Widdra1,2 — 1Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany — 2Max-Planck-Institute für Mikrostrukturphysik, Halle (Saale), Germany
Unoccupied electronic states of ultrathin cobalt oxide films grown on Ag(001) are studied by time- and angle-resolved two-photon photoemission (2PPE) spectroscopy. With pump/probe photon energies of 4.2 and 1.8 eV, a series of states at 3.55, 3.87 and 4.00 eV above EF could be identified. The strongest feature at 3.55 eV is assigned as n=1 image potential (IP) state of ultrathin CoO films due to its characteristic parabolic dispersion. At the Γ point, the IP state has a lifetime of approximately 35 fs. Additionally to the IP states near the vacuum level, an unoccupied CoO conductive band state has been found at 2.3 eV above EF with a lifetime below 30 fs. Our results are discussed with the theoretical electronic structure of CoO and compared with results for NiO films.