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 Mn_xO_y 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 Mn_xO_y 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 Mn_xO_y films up to 6 ML is performed by STM and by noncontact-AFM. The latter allows also imaging of insulating films.