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Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 75: Oxides and Insulators: Epitaxy and Growth

O 75.5: Talk

Thursday, February 28, 2008, 16:15–16:30, MA 042

Growth of well-ordered MnxOy films on Pt(111): An in-vivo STM/STS study at elevated temperatures — •Benjamin Bochmann, Christian Hagendorf, Steffen Sachert, and Wolf Widdra — Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle

Growth behavior as well as atomic and electronic structure of ultra thin epitaxial manganese oxide films on Pt(111) have been studied using STM/STS and LEED. The films have been prepared by reactive deposition of manganese in an oxygen atmosphere of 10−8 to 10−6 mbar. STM measurements performed during growth (in vivo) at elevated temperatures (400-600 K) reveal three different well-ordered monolayer structures depending on the preparation conditions: At lowest oxygen pressure a (19 × 1) uniaxially reconstructed MnO(100)-like layer is formed. STM data which resolve all atoms within one sublattice reveal details of the reconstruction. At higher oxygen pressure, an intermediate MnxOy monolayer grows. It is complex, but characterized by sharp LEED pattern which corresponds with atomically resolved STM images of the periodic 1,5 nm × 1,5 nm unit cell structure. Under highly oxidizing conditions a quasi-hexagonal monolayer with MnO2 stoichiometry is formed. LEED shows sharp satellite peaks which can be understood as a Moiré structure with 7% misfit to the Pt(111) substrate. STM images indicate a wagon wheel like reconstruction. The characterization of thicker MnxOy films up to 6 ML is performed by STM and by noncontact-AFM. The latter allows also imaging of insulating films.

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