Control of the in-plane epitaxy for bi-epitaxial grain boundary junctions using a new multilayer structure

Abstract

In order to obtain 100% bi-epitaxial 45° grain boundary junctions of YBa2Cu3Ox (YBCO), we have systematically examined the in-plane epitaxy of CeO2 films grown on MgO substrates. The inevitable presence of CeO2[110]∥MgO[100] causes mixtures of in-plane rotation of 0° and 45° between YBCO/CeO2/MgO and YBCO/MgO. We have further developed a new structure, namely YBCO/CeO2/Yttria-stabilized ZrO2/MgO and YBCO/MgO boundary, so that 100% in-plane rotation of 45° can be routinely obtained. The model of the in-plane epitaxial relationship between the multilayers using near coincident site lattices was proposed. The critical current density of the junctions made on the boundary is 3×103 A/cm2 at 77 K, while the order of the Jc of YBCO films on both sides of the grain boundary is 106 A/cm2. The current-voltage characteristics of the junctions show resistively shunted junction behavior. The better epitaxy of our new structure can lead to a better control of grain boundary critical current density.

Grain boundaries in high-Tcsuperconductors

“…1 See, for example, Ijsselsteijn et al, 1993Ijsselsteijn et al, , 1994Vollnhals et al, 1994;Li et al, 1995;Petersen, Stolzel, et al, 1995;Boikov et al, 1997aBoikov et al, , 1997bY. Chen et al, 1997;Horng et al, 1997;Villegier, 1997a, 1997b;Tsaiet al, 1998.…”

YBa2Cu3O7−δ long Josephson junctions on bicrystal Zr1−xYxO2 substrates fabricated by preliminary topology masks

“…The aim was to obtain two areas of YBCO film whose crystal axes are turned relative to each other by 45 degrees in the a-b plane. In the work [8] a similar bi-epitaxial grain boundary was obtained between YBCO/CeO 2 /YSZ/MgO and YBCO/MgO, but the topology of the superconducting structures in these papers was formed by ion or chemical etching.…”