Direct Imaging of Tilts and Rotations of Ca<sub>2</sub>RuO<sub>4</sub> Octahedra in Thin Films with Epitaxial Strain using ABF-STEM

ORAL

Abstract

Recent studies on thin film Ca2RuO4 grown on LaAlO3, NdAlO3, and NdGaO3 substrates show that tuning epitaxial strain can control the tilt and rotation of the RuO6 octahedra. This leads to change in electronic properties such as the d-band bandwidth, electrical resistivity, and the metal-to-insulator transition temperature. Quantifying the exact structural distortions of RuO6 is therefore crucial in understanding the correlation between structure modification and electronic properties. In this work we use Annular Bright Field imaging (ABF) in Scanning Transmission Electron Microscopy (STEM) to directly locate the atom positions with picometer precision. Average Ru-O-Ru bond angles are mapped layer by layer to characterize the degree of tilt relaxation and decay lengths as we move away from the strained interface. We also compare distortions of the octahedra for different epitaxially strained states.

*This work made use of the Cornell Center for Materials Research Shared Facilities which are supported through the NSF MRSEC program (DMR-1719875). This work is also supported by NSF fellowship (DGE-1650441).

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Presenters

  • Celesta Chang

    • Department of Physics, Cornell University

Authors

  • Celesta Chang

    • Department of Physics, Cornell University

  • Megan Holtz

    • School of Applied and Engineering Physics, Cornell University

  • Hari Nair

    • Department of Materials Science and Engineering, Cornell University
    • Cornell Univ
    • Materials Science and Engineering, Cornell University

  • Jacob Ruf

    • Department of Physics, Cornell University

  • Kyle Shen

    • Physics, Cornell University
    • Department of Physics, Cornell University
    • Laboratory of Atomic and Solid State Physics, Cornell University
    • Cornell University
    • Cornell Univ

  • Darrell Schlom

    • Materials Science, Cornell University
    • Department of Materials Science and Engineering, Cornell University
    • Department of Material Science and Engineering, Cornell University
    • Cornell University
    • Cornell Univ
    • Materials Science and Engineering, Cornell University

  • David Muller

    • Cornell University
    • School of Applied and Engineering Physics, Cornell University
    • Applied Engineering Physics, Cornell University
    • Cornell Univ