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O: Oberflächenphysik

O 48: Oxide und Isolatoren II

O 48.10: Vortrag

Dienstag, 8. März 2005, 18:00–18:15, TU EB107

A Tensor LEED Structure Determination of a CoO Ultrathin Film on Ag(100) — •Karl-Michael Schindler, Jian Wang, Wolf Widdra, and Henning Neddermeyer — Martin-Luther-Universität Halle-Wittenberg, FB Physik, D-06099 Halle, Germany

A four monolayer thick CoO film has successfully be grown in nearly layer by layer mode on a Ag(100) substrate by evaporating Co in 10⁻⁶ mbar oxygen with the substrate heated to 470 K. Previous LEED and STM investigations have shown that such films grow pseudomorphic i.e. the CoO accepts the lattice of the substrate, Furthermore, they exhibit maximal long range order and minimal variation in thickness. This makes them the most suitable systems for a structure determination by the analysis of LEED I(V) curves. The one of this study is based on the measurement of 5 inequivalent beams in the range from 30 to 400 eV, with a total energy range of 1025 eV. The calculation of the I(V) curves was performed using the Barbierie-van Hove Symmetrized Automated Tensor LEED(SATLEED) package. As an initial structure bulk values were assumed for the Ag substrate and the CoO film. Regarding the lattice relations at the interface, all three possibilities of high symmetry were tried as initial model structures. In addition films with a thickness of 2, 3, 4, and 5 layers were tried. In the optimization the z positions of the atoms in the two topmost layers, the distance between the CoO film and the Ag substrate, the inner potential and the Debey temperatures were optimized. The structural results of the best-fit model (r-factor: 0.20) will be discussed in comparison to related systems.