title: Phonons in Ultrathin Oxide Films: 2D to 3D Transition in FeO on Pt(111).
abstract: The structural and magnetic properties of ultrathin FeO(111) films on Pt(111) with thicknesses from 1 to 16 monolayers (MLs) were studied using the nuclear inelastic scattering of synchrotron radiation. A distinct evolution of vibrational characteristics with thickness, revealed in the phonon density of states (PDOS), shows a textbook transition from 2D to 3D lattice dynamics. For the thinnest films of 1 and 2 ML, the low-energy part of the PDOS followed a linear ∝E dependence in energy that is characteristic for two-dimensional systems. This dependence gradually transforms with thickness to the bulk ∝E^{2} relationship. Density-functional theory phonon calculations perfectly reproduced the measured 1-ML PDOS within a simple model of a pseudomorphic FeO/Pt(111) interface. The calculations show that the 2D PDOS character is due to a weak coupling of the FeO film to the Pt(111) substrate. The evolution of the vibrational properties with an increasing thickness is closely related to a transient long-range magnetic order and stabilization of an unusual structural phase.
authors.affiliation: Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków, Poland.
authors.forename: N
authors.initials: N
authors.lastname: Spiridis
authors.affiliation: European Synchrotron Radiation Facility (ESRF), P.O. Box 220, F-38043 Grenoble, France.|Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Zając
authors.affiliation: Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Kraków, Poland.
authors.forename: P
authors.initials: P
authors.lastname: Piekarz
authors.affiliation: European Synchrotron Radiation Facility (ESRF), P.O. Box 220, F-38043 Grenoble, France.
authors.forename: A I
authors.initials: AI
authors.lastname: Chumakov
authors.affiliation: Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Freindl
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005, Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: Goniakowski
authors.affiliation: Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Kozioł-Rachwał
authors.affiliation: Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Kraków, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Parliński
authors.affiliation: Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Ślęzak
authors.affiliation: Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
authors.forename: T
authors.initials: T
authors.lastname: Ślęzak
authors.affiliation: Institute of Technology, Pedagogical University, ul. Podchorążych 2, 30-084 Kraków, Poland.
authors.forename: U D
authors.initials: UD
authors.lastname: Wdowik
authors.affiliation: Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków, Poland.
authors.forename: D
authors.initials: D
authors.lastname: Wilgocka-Ślęzak
authors.affiliation: Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków, Poland.|Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
authors.forename: J
authors.initials: J
authors.lastname: Korecki