Investigation of flux state in high-Tc junctions and circuits based on multilayer structures having oxygen via holes by a scanning SQUID microscope

Abstract We have investigated the flux state in high-Tc circuits based on multilayer structures including La-doped YBCO (La-YBCO) ground plane by a scanning SQUID microscope (SSM) system. The circuits contained via holes in the insulating layer and the ground plane. They were post-annealed in flowing oxygen under various conditions such as the annealing temperature and the annealing time. It was found that the flux state depends on the post-annealing temperature strongly, and in the case of annealing at temperatures lower than 500 °C, oxygen is not provided into the ground plane sufficiently. Moreover, we found that oxygen via holes are necessary to provide oxygen sufficiently into the ground plane, and an appropriate via hole configuration is needed for homogeneous oxidation.