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Emergent Structural and Vibrational Properties in SrTiO<sub>3</sub>-CaTiO<sub>3</sub> Superlattices using Atomic-resolution Microscopy and Theory

ORAL

Abstract

Perovskite oxides offer an abundance of properties with technological importance that are tunable by creating superlattices (SLs). Most research so far focuses on electronic properties, but such SLs can also feature unique thermal properties, which are dictated by lattice vibrations [1]. Here we combine atomic-resolution scanning-transmission-electron microscopy, vibrational electron energy-loss spectroscopy, and density-functional-theory calculations to probe the phonon spectra of a series of SrTiO3-CaTiO3 SLs with 1 to 27 unit-cells per layer. We show large-period SLs feature bulk plus localized interface vibrational modes. As layer thickness decreases, the bulk modes disappear while the interface modes underpin an emergent phonon structure, which is also reflected in the macroscopic vibrational response. This behavior correlates to period thickness reaching the length scale of octahedral coupling at the interfaces, thus reflecting the dominant role of interfaces as size decreases and the need for spatially quantified structural and vibrational data to enable complete understanding of SL behavior.
[1] J. Ravichandran et al., Nature Materials (2014).

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Presenters

  • Eric Hoglund

    Department of Materials Science and Engineering, University of Virginia

Authors

  • Eric Hoglund

    Department of Materials Science and Engineering, University of Virginia

  • Jordan A Hachtel

    Oak Ridge National Lab, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory

  • Thomas E Beechem

    Sandia National Laboratories

  • Deliang Bao

    Vanderbilt Univ, Institute of Physics, Chinese Academy of Sciences, Department of Physics and Astronomy, Vanderbilt University, Chinese Academy of Sciences,Institute of Physics

  • Zachary T Piontkowski

    Sandia National Laboratories

  • Joshua Caldwell

    Vanderbilt Univ, Department of Mechanical Engineering and Electrical Engineering, Vanderbilt University

  • Jon F Ihlefeld

    Department of Materials Science and Engineering, University of Virginia

  • Jayakanth Ravichandran

    Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Department of Chemical Engineering and Materials Science, University of Southern California

  • Andrew O'Hara

    Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA, Department of Physics and Astronomy, Vanderbilt University, Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, Vanderbilt University

  • Joseph R Matson

    Department of Mechanical Engineering and Electrical Engineering, Vanderbilt University

  • Ramamoorthy Ramesh

    materials science and engineering, university of california berkeley, University of California, Berkeley, University of California Berkeley, UC Berkeley, Department of Materials Science and Engineering, University of California Berkley

  • Sokrates T Pantelides

    Department of Physics and Engineering, Vanderbilt University, Department of Physics and Astronomy, Vanderbilt Univ, Department of Physics and Astronomy, Vanderbilt University, Vanderbilt Univ, Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA, Institute of Physics, Chinese Academy of Sciences, Department of Physics and Astronomy & Department of Electrical Engineering and Computer Science, Vanderbilt University, Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN, Department of Electrical Engineering and Computer Science, Vanderbilt University, Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University, Vanderbilt University

  • Patrick E Hopkins

    Department of Mechanical Engineering, University of Virginia

  • James M Howe

    Department of Materials Science and Engineering, University of Virginia