YBCO artificial grain boundary junctions on Si

Si bicrystal substrates with different misorientation angles were fabricated using the hot-press method and their qualities were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). YBa/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) epitaxial thin films were grown on such substrates by RF magnetron sputtering, with yttria and yttria-stabilized zirconia as the buffer layers. The properties of bridge-type junctions patterned on the film by an excimer laser were studied from 4.2 K to 77 K. It was found that the critical current density of the artificial grain boundary (AGB) junction (J/sub c//sup A/) was always less than that of the junction made on Si single-crystal grains (J/sub c//sup G/). The (J/sub c//sup A/)/(J/sub c//sup G/) ratio decreased exponentially as the misorientation angle ( theta ) was increased. The effect of temperature and microwave irradiation showed that the properties of AGB junctions with theta <5 degrees were limited by flux creep. In contrast, AGB junctions with theta >or=10 degrees showed the Josephson effect.<
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