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O: Fachverband Oberflächenphysik
O 79: Oxide Surfaces III
O 79.1: Vortrag
Donnerstag, 14. März 2013, 16:00–16:15, H45
Identification of the surface phonons of BaTiO3(100) and ultrathin films of BaTiO3 on metal substrates — •Florian Schumann1, Klaus Meinel1, Andreas Trützschler1, Konrad Gillmeister1, and Wolf Widdra1,2 — 1Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle — 2Max-Planck-Institut für Mikrostrukturphysik, Halle
Phonons and their softening are key elements for the understanding of the long range coupling in ferroelectric and multiferroic materials which causes, e.g., the paraelectric to ferroelectric phase transition. In thin films these ferroelectric properties are often controlled by strain from the underlying substrate or heterostructure. Here we study the surface phonons of a BaTiO3(100) single-crystal and of BaTiO3(100) thin films grown by MBE and magnetron sputtering on Pt(100) and Au(100). HREELS spectra for all cases are dominated by three well-developed phonon peaks at about 220, 460, and 650 cm−1. The latter two are identified as A(TO) surface modes. For thin films on Pt(100) and on Au(100) shifts of the surface phonons are observed due to misfit strain of +2% and -2%, respectively, as compared to the single crystal. Changes of the vibrational properties due to film thickness and temperature will be discussed.