Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 25: Oxide and Insulator Surfaces: Structure and Growth
O 25.4: Poster
Monday, March 7, 2016, 18:15–20:30, Poster E
Complex dielectric function of SrTiO3 and BaTiO3 by HREELS — •Florian Schumann1, Klaus Meinel1, 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 phase transitions in ferroelectrics and multiferroics. In thin films, the phonons depend sensitively as well as the phase transition temperatures on the strain within the film. Here we report on high-resolution electron energy loss spectroscopy (HREELS) on the (001) and (111) surfaces of BaTiO3 and SrTiO3. HREELS reveals three dipole-active phonon polaritons, which are derived from the known transversal optical bulk phonons. In addition, it will be demonstrated that the complex dielectric function in the energy range from 4 to 1000 meV can be quantitatively extracted from the experimental loss function. This opens up the additional characterization of oxide doping levels as will be discussed for single crystal surfaces and thin films down to one unit cell thickness.