Growth, atomic structure, and vibrational properties of MnO ultrathin films on Pt(111)

Ultrathin films of MnO have been grown by reactive metal deposition in an O-2 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 (19x1) periodicity, which results in rotational domains on the hexagonal Pt(111) substrate. Growth and structural properties of the (19x1) 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 vibration of the O sublattice against the Mn sublattice based on the O-16 to O-18 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).