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Detailed microstructure analysis of epitaxial thin films is a vital step towards understanding essential structure-property relationships. Here, a combination of transmission electron microscopy (TEM) techniques is utilized to determine in detail the microstructure of epitaxial La-doped BaSnO3 films grown on two different perovskite substrates: LaAlO3 and PrScO3. These BaSnO3 films are of high current interest due to outstanding electron mobility at ambient. The rotational disorder of low-angle grain boundaries, namely the in-plane twist and out-of-plane tilt, is visualized by conventional TEM under a two-beam condition, and the degree of twists in grains of such films is quantified by selected-area electron diffraction. The investigation of the atomic arrangement near the film-substrate interfaces, using high-resolution annular dark-field scanning TEM imaging, reveals that edge dislocations with a Burgers vector along  result in the out-of-plane tilt. It is shown that such TEM-based analyses provide detailed information about the microstructure of the films, which, when combined with complimentary high-resolution X-ray diffraction, yields a complete structural characterization of the films. In particular, stark differences in out-of-plane tilt on the two substrates are shown to result from differences in misfit dislocation densities at the interface, explaining a puzzling observation from X-ray diffraction.
Bibliographical noteFunding Information:
This work was supported primarily by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013, and partially by DMR-1741801 and the Grant-in-Aid program of the University of Minnesota. Part of this work was carried out in the College of Science and Engineering Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC. H. Y. acknowledges a fellowship from the Samsung Scholarship Foundation, Republic of Korea.
© 2018 The Author(s).
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PubMed: MeSH publication types
- Journal Article
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