Showing papers by "Jian Chen published in 1991"

YBa2Cu3O7-δ Angle Grain Boundary Junction on Si Bicrystal Substrate

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 (JcA) is always less than that of either bridge made on single-crystal grains (JcG). 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.

Artificial YBCO grain boundary junctions on SrTiO3 and Si bicrystals

Abstract: Bicrystal substrates of SrTiO3 and Si were made and artificial angled-grain boundary Josephson junctions were made on both substrates In order to form an angled-grain boundary structure artificially, which contributes effectively as a Josephson junction, (0 0 1)SrTiO3 and (0 0 1)Si bicrystal substrates were fabricated by diffusion bonding of the two single crystals YBCO films were epitaxially grown by MOCVD and RF magnetron sputtering on SrTiO3 and Si bicrystal substrates, respectively The bridges crossing the boundaries were patterned by excimer laser etching Both types of bridge responded to microwave irradiation A bridge with 20 degrees angled-grain boundary and Ic of about 100 mu A on an SrTiO3 bicrystal showed Shapiro steps up to the fourth order for RF=84 GHz at 69 K, and a bridge with 10 degrees boundary and Ic of about 08 mA on an Si bicrystal showed Shapiro steps up to 05 mV for RF=96 GHz at 77 K