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O: Fachverband Oberflächenphysik

O 75: Oxides and Insulators: Epitaxy and Growth

O 75.6: Vortrag

Donnerstag, 28. Februar 2008, 16:30–16:45, MA 042

Vibrational and electronic properties of ultrathin MnO(100) films — •Sebastian Polzin¹, Steffen Sachert¹, Krassimir Kostov², and Wolf Widdra¹ — ¹Martin-Luther-Universität Halle-Wittenberg, Institute of Physics, Halle — ²Bulgarian Academy of Science, Sofia, Bulgaria

The vibrational properties of ultrathin MnO(100) films on Pt(111) have been studied using high-resolution electron energy loss spectroscopy (HREELS). It was found that the strong optical phonon of the 1st monolayer at 368 cm^-1 shifts to 382 cm^-1 with increasing coverage up to 2 ML. At coverages above 1 ML a new phonon at 547 cm^-1 is observed and identified as Fuchs-Kliewer phonon. Isotopic ¹⁶O/¹⁸O substitution reveales that a collective vibration of the oxygen against the manganese sublattice causes both phonons. For film thickness’ up to 13 ML the Fuchs-Kliewer phonon shifts down to 539 cm^-1.

Electronic excitations in the energy range of 0-7.5 eV show well defined and narrow d-d band excitations for MnO(100) films from 1 to 10 ML. They converge nicely with increasing thickness towards MnO(100) single crystal data [1].

[1] B. Fromme et al., Phys. Rev. B 58, 9783 (1998).