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Interface dipole between two metallic oxides caused by localized oxygen vacancies

Albina Y. Borisevich, Andrew R. Lupini, Jun He, Eugene A. Eliseev, Anna N. Morozovska, George S. Svechnikov, Pu Yu, Ying-Hao Chu, Ramamoorthy Ramesh, Sokrates T. Pantelides, Sergei V. Kalinin, and Stephen J. Pennycook
Phys. Rev. B 86, 140102(R) – Published 11 October 2012
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    Abstract

    Oxygen vacancies are increasingly recognized to play a role in phenomena observed at transition-metal oxide interfaces. Here, we report a study of SrRuO3 and La0.7Sr0.3MnO3 interfaces using a combination of quantitative aberration-corrected scanning transmission electron microscopy, electron energy-loss spectroscopy, and density functional calculations. Cation displacements are observed at the interface, indicative of a dipolelike electric field even though both materials are nominally metallic. The observed displacements are reproduced by theory if O vacancies are present in the near-interface La0.7Sr0.3MnO3 layers. The results suggest that atomic-scale structural mapping can serve as a quantitative indicator of the presence of O vacancies at interfaces.

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    • Received 31 October 2011

    DOI:https://doi.org/10.1103/PhysRevB.86.140102

    ©2012 American Physical Society

    Authors & Affiliations

    Albina Y. Borisevich1,*, Andrew R. Lupini1, Jun He1,2, Eugene A. Eliseev3, Anna N. Morozovska4, George S. Svechnikov4, Pu Yu5, Ying-Hao Chu6, Ramamoorthy Ramesh5, Sokrates T. Pantelides2,1, Sergei V. Kalinin1, and Stephen J. Pennycook1,2

    • 1Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
    • 2Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA
    • 3Institute for Problems of Materials Science, National Academy of Science of Ukraine, 3, Krjijanovskogo, 03142 Kiev, Ukraine
    • 4Institute of Semiconductor Physics, National Academy of Science of Ukraine, 41, pr. Nauki, 03028 Kiev, Ukraine
    • 5Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, California, 94720, USA
    • 6Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan 30013, Republic of China

    • *Corresponding author: albinab@ornl.gov

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    Vol. 86, Iss. 14 — 1 October 2012

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    Images

    • Figure 1
      Figure 1
      (a) HAADF image of the SrRuO3–La0.7Sr0.3MnO3 interface (b) integrated intensities of La M4,5 and Mn L2,3 edges across the interface illustrating interface sharpness and effective (La,Sr)O-RuO2 termination; a line profile of the ADF image (background subtracted) is given in light gray for comparison. (c) and (e) Two-dimensional maps of the (c) out-of-plane, or c and (e) in-plane, or a pseudocubic lattice parameters computed from Fig. 1a. (d) and (f) Profiles of the maps in (c) and (e) calculated by averaging along the interface. In Fig. 1d, cross-hatched rectangles cover the points that do not show statistically significant changes (see text). Error bars in profiles (d) and (f) show standard deviation with respect to averaging along the interface in the maps (c) and (e).Reuse & Permissions
    • Figure 2
      Figure 2
      (a) and (b) 2D maps of the (a) out-of-plane, or X and (b) in-plane, or Y Mn/Ru cation displacements computed from Fig. 1a. (c) Profile of the map in (a) calculated by averaging along the interface. In Fig. 2c, cross-hatched rectangles cover the points that do not show statistically significant changes (see text). Error bars in profile (c) show standard deviation with respect to averaging along the interface in the map (a).Reuse & Permissions
    • Figure 3
      Figure 3
      Polarization (a), electric field (b), potential (c), and effective charge density (d) profiles reconstructed from experimental atomic displacement data. Filled symbols in (a)–(d) are calculated from experimental atomic displacement data [Fig. 1c]. Solid curves are calculated self-consistently for material parameters in text.Reuse & Permissions
    • Figure 4
      Figure 4
      (a) Mn/Ru cation displacement profiles generated from density functional calculations for (La,Sr)O-RuO2-terminated surface: free-electron doped (black squares), with one oxygen vacancy on the La0.7Sr0.3MnO3 side [red (dark gray) squares], and with two oxygen vacancies on the La0.7Sr0.3MnO3 side [blue (medium gray) squares]. (b) View of the interface in the structure model with two oxygen vacancies [denoted by red (dark gray) circles] showing the best agreement with the experiment; blue (medium gray) and yellow (light gray) lobes next to oxygen atoms show increase and decrease, respectively, in the electron density compared to the model without vacancies. (c) The difference between planar averaged electric potentials for the case with two vacancies [model in Fig. 4b] vs no vacancies.Reuse & Permissions
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