YBCO ARTIFICIAL GRAN BOUNDARY JUNCTIONS ON Si

Si bicrystal substrates with different misorientation angles were fabricated using the hot-press method and their qualities were examined by SEM, TEM and XRD. YBa2Cu3O7-delta(YBCO) epitaxial thin films were grown on such substrates by rf magnetron sputtering, with yttria (Y2O3) and yttria-stabilized zirconia(YSZ) as the buffer layers. The properties of bridge type junctions patterned on the film by an excimer laser were studied from 4.2K to 77K It was found that the critical current density of the artificial grain boundary(AGB) junction (J(C)A) was always less than that of the junction made on Si single-crystal grains (J(C)G). The ratio J(C)A/J(C)G 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 >= 10 degrees showed the Josephson effect. Clear Shapiro steps and Josephson mixing were observed at 77K.