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.