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2008
Journal Article
Titel
Growth, atomic structure, and vibrational properties of MnO ultrathin films on Pt(111)
Abstract
Ultrathin films of MnO have been grown by reactive metal deposition in an O2 atmosphere on Pt(111) and studied using scanning tunneling microscopy (STM), low-energy electron diffraction, temperature programmed desorption, and high-resolution electron energy loss spectroscopy. In situ STM experiments which have been performed during film growth at elevated temperatures show that MnO grows highly ordered in a layerlike mode on Pt(111). The first MnO monolayer exhibits large, uniaxial reconstructed domains with a (19×1) periodicity, which results in rotational domains on the hexagonal Pt(111) substrate. Growth and structural properties of the (19×1) reconstruction are discussed in a model based on long-range ordering of antiphase boundaries within a uniaxially reconstructed and otherwise bulklike MnO(001) monolayer. The vibrational spectra for the MnO monolayer are dominated by a strong and narrow surface phonon peak at 368 cm-1, which is identified as the out-of-plane vib ration of the O sublattice against the Mn sublattice based on the O16 to O18 isotope shift. After completion of the MnO monolayer, multilayer growth mode is found at higher coverages (>1.5 ML). The appearance of the second MnO layer is accompanied by an additional Fuchs-Kliewer phonon mode at 545 cm-1.