Lattice mismatch effects on the hetero interface structure of YBCO films grown by liquid phase epitaxy

Yoshihiro Sugawara, Yuichi Ikuhara, Tasuku Kitamura, Izumi Hirabayashi

    Research output: Contribution to journalArticlepeer-review

    7 Citations (Scopus)

    Abstract

    Electronic and magnetic properties of oxide superconducting films grown on a substrate strongly depend on the film/substrate interface. In this study, the lattice mismatch effects on the interface structure of YBCO films grown by liquid phase epitaxy were investigated by characterizing two model systems. These two systems, YBCO/ NdGaO3(f: 0.84∼0.90%) and YBCO/MgO(f: 9.1∼25%), differ by their small and large lattice mismatches, respectively. In the case of the YBCO/NdGaO3 interface, misfit dislocation network is introduced to accomodate lattice strain along the interface. The misfit dislocations are composed of [110]NdGaO3, [002]NdGaO3, and [100]YBCO edge type dislocations depending on the crystal orientation, and hence extra half planes exist both in NdGaO3 and YBCO crystals. The orthogonal sets of misfit dislocations are dissociated to form nodes which also have an edge component. The critical current density Jci in the YBCO film is as low as 9.0 × 102 A/cm2 at 77 K in 1 T. In the case of the YBCO/MgO interface, geometrical misfit dislocations are formed at the interface. The geometrical misfit dislocations accompany local lattice bending in the vicinity of the interface. In the YBCO film, a high density of edge dislocations with their Burgers vector perpendicular to the interface exist, which result in the formation of stacking faults on the ab plane in the YBCO crystals. Such defects may be introduced during crystal growth by following the local lattice bending due to the geometrical misfit dislocation. The Jci in the YBCO film is as high as 5.4 × 105 A/cm2 at 77 K in 1 T. The difference in critical current densities between two specimens presumably originates from the density of pinning centers for magnetic flux in YBCO crystals.

    Original languageEnglish
    Pages (from-to)942-950
    Number of pages9
    JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
    Volume61
    Issue number9
    DOIs
    Publication statusPublished - 1997

    Keywords

    • Critical current density
    • Geometrical misfit dislocation
    • Liquid phase epitaxy
    • Misfit dislocation network
    • Stacking fault
    • Transmission electron microscopy
    • YBCO film

    ASJC Scopus subject areas

    • Condensed Matter Physics
    • Mechanics of Materials
    • Metals and Alloys
    • Materials Chemistry

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