Ferroelectricity in CaTiO$_{3}$ Single Crystal Surfaces and Thin Films and Probed by Nonlinear Optics and Raman Spectroscopy

ORAL

Abstract

Bulk CaTiO$_{3}$ has a centrosymmetric point group and is \textit{not }polar or ferroelectric. However, we present surprising results that show highly regular polar domains in single crystals of CaTiO$_{3}$. Confocal Second Harmonic Generation (SHG) and Raman imaging studies were carried out on perovskite CaTiO$_{3}$ crystal surfaces. They reveal large, crystallographic polar domains at room temperature, with in-plane polarization components delineated by twin walls. SHG analysis indicates that the highest symmetry of the polar surface is $m $(space group P$c)$ with polarization in the $m$ plane. In addition, we present results of the polar domain structure imaged before and after the application of an external electric field. Finally, we present the SHG studies of CaTiO$_{3}$ thin films grown using reactive Molecular Beam Epitaxy (MBE); these films are predicted by theory to be ferroelectric and are shown experimentally, both with SHG and in-plane dielectric measurements, to be ferroelectric for temperatures less than $\sim $150 K with group symmetry \textit{mm}2.

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Authors

  • Eftihia Vlahos

    The Pennsylvania State University, Pennsylvania State University, University Park, Pennsylvania 16802, USA

  • Tom Lummen

    The Pennsylvania State University, Pennsylvania State University, University Park, Pennsylvania 16802, USA

  • Ryan Haislmaier

    The Pennsylvania State University

  • Sava Denev

    The Pennsylvania State University, The Pennsylvania State University, University Park, PA, Pennsylvania State University, University Park, Pennsylvania 16802, USA

  • Charles Brooks

    The Pennsylvania State University

  • M.D. Biegalski

    Oak Ridge National Lab, Oak Ridge National Laboratory

  • Darrell Schlom

    Cornell University, Cornell University, NY

  • Carl-Johan Eklund

    Rutgers University

  • Karin M. Rabe

    Rutgers University, Department of Physics and Astronomy, Rutgers University

  • Craig Fennie

    Cornell University, Cornell University, NY, School of Applied and Engineering Physics, Cornell University, School of Applied and Engineering Physics, Cornell University, Ithaca, NY

  • Venkatraman Gopalan

    The Pennsylvania State University, The Pennsylvania State University, University Park, PA, Pennsylvania State University, Pennsylvania State University, University Park, Pennsylvania 16802, USA