Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 33: Oxides and Insulators: Epitaxy and Growth
O 33.5: Vortrag
Dienstag, 27. März 2007, 16:45–17:00, H41
Layer-resolved study of the local electronic structure of ultrathin NiO(001) films on Ag(001): A STS and DFT study — •S. Grosser1, Chr. Hagendorf1, M. Däne1, A. Ernst2, M. Lüders3, Z. Szotek3, W. M. Temmerman3, W. Hergert1, and W. Widdra1 — 1Martin-Luther-Universität Halle-Wittenberg, Institute of Physics, Halle — 2MPI for Microstructure Physics, Halle — 3Daresbury Laboratory, Warrington, U.K.
Scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional theory (DFT) have been applied to study the local electronic and atomic structure of thin NiO films on Ag(001). Differential conductance spectra (dI/dV) for precursor phases, oxide bilayer and thin oxide films up to 5 ML exhibit distinct differences in the electronic structure. The region of the unoccupied states up to 4 eV above EF is dominated by the local density of states within the oxide film. Especially for 2 ML islands and thicker films strong and well-resolved unoccupied Ni 3d-states are found. At energies above 4.5 eV, the experimental spectra exhibit strong field emission resonances which are characteristically modified by the thickness-dependent oxide band structure. The experimental determined electronic structure will be compared with DFT calculations considering also different magnetic ordering within the NiO film. The strong electron correlation effects in the oxide are taken into account via self-interaction corrections. The calculated layer-dependent evolution of the NiO electronic structure and the appearance of a Ni 3d-derived surface state compare well with the experimental results.