YBa2Cu3O7-δ Angle Grain Boundary Junction on Si Bicrystal Substrate

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Abstract
Si bicrystal substrates with angle grain boundaries (AGB) have been fabricated for the first time by a diffusion bonding technique using the hot-press method. YBa2Cu3O7-δ (YBCO) epitaxial thin films are grown on the Si bicrystal substrates with yttria (Y2O3) and yttria-stabilized zirconia (YSZ) buffer layers by rf magnetron sputtering. The properties of bridge-type junctions patterned by excimer laser have been studied from 4.2 K to 77 K and by microwave irradiation. It is found that the critical current density of the AGB junction (J c A) is always less than that of either bridge made on single-crystal grains (J c G). The effects of the temperature and microwave radiation show that the properties of the bridges on the grains are limited by flux creep. In contrast, the properties of the AGB junction with the angle larger than 10° show the Josephson effect.