Microstructure of a high Jc, laser-ablated YBa2Cu3O7-δ/sol-gel deposited NdGaO3 buffer layer/(001) SrTiO3 multi-layer structure

Chau Yun Yang, Ataru Ichinose, S. E. Babcock, J. S. Morrell, J. E. Mathis, D. T. Verebelyi, M. Paranthaman, D. B. Beach, D. K. Christen

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    Abstract

    A YBa2Cu3O7-δ (YBCO) film with a transport critical current density (Jc) value of 1 mA/cm2 (77 K, 0 T) was grown on a solution deposited NdGaO3 (NGO) buffer layer on (100) SrTiO3 (STO). The 25-nm thick NGO buffer layer was dip-coated onto the STO single crystal from a solution of metal methoxyethoxides in 2-methoxyethanol. Pulsed laser deposition (PLD) was used to grow a 250-nm-thick YBCO film on the NGO. The epitaxial relationships are cube-on-cube throughout the structure when the pseudo cubic and pseudo tetragonal unit cells are used to describe the NGO and YBCO crystal structures, respectively: (001) YBCO ∥ (001) NGO ∥ (001) STO and [100] YBCO ∥ [100] NGO ∥ [100] STO. High resolution scanning electron microscopy (SEM) of the bare NGO surface revealed approx. 40 nm diameter pinholes with number density of approx. 2 × 1013 m-2, corresponding to an area fraction coverage of 2.5%, in an otherwise featureless surface. Cross-sectional transmission electron microscopy (TEM) showed that these pinholes penetrate to the STO; otherwise the NGO layer was uniformly thick to within approximately ±5 nm and defect free. The X-ray diffraction φ- and ω-scans indicated that the YBCO film was highly oriented with a full-width-half maximum peak breadth of 1.14° for in-plane and 0.46° for out-of-plane alignment, respectively. The film contained sparse a-axis oriented grains, an appreciable density of (001) stacking faults and apparently insulating second phase precipitates of the type that typically litter the surface of PLD films. All of these defects are typical of YBCO thin films. High-resolution cross-sectional TEM images indicate that no chemical reaction occurs at the YBCO/NGO interface.

    Original languageEnglish
    Pages (from-to)73-78
    Number of pages6
    JournalPhysica C: Superconductivity and its Applications
    Volume331
    Issue number1
    DOIs
    StatePublished - Apr 1 2000

    Funding

    This work was supported by the US Department of Energy and National Science Foundation-MRSEC at the University of Wisconsin-Madison. The research performed at ORNL was sponsored by the Division of Materials Sciences, Office of Basic Energy Sciences, and the Office of Energy Efficiency and Renewable Energy. The Oak Ridge National Laboratory is managed by Lockheed Martin Energy Research for the US Department of Energy under contract number DE-AC05-96OR22464.

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