Fabrication of HTS ramp-edge-type Josephson junctions and SQUIDs using various YBCO-derivatives as barrier materials

New barrier materials have been tried to be used for fabrication of ramp-edge-type Josephson junctions (JJs) and SQUIDs in which La0.1Er0.95Ba1.95Cu3Oy and SmBa2Cu3Oy are used as counter- and base-electrodes, respectively. The derivatives having the YBCO-type structure with a variety of lattice size, Al0.5Sr2Y0.5Ca0.5Cu2.4Zn0.1Oy, Mo0.5BaSrPr0.5Yb0.5Cu2.4Zn0.1Oy, Yb0.9La0.2Ba1.9Cu3Oy, Pr1.4Ba1.6Cu2.6Ga0.4Oy, La1.5Ba1.5Cu3Oy and TaBa2LaCu2Oy were examined. The structure and composition around the barrier region were investigated using an analytical transmission electron microscope for a sample prepared using the Yb0.9La0.2Ba1.9Cu3Oy barrier material. It was suggested that an oxygen-deficient perovskite phase exhibiting metallic conduction was crystallized in the barrier region. When TaBa2LaCu2Oy was used, large IcRn's around 200 μV and SQUID modulation voltages larger than 40 μV were observed. The attained large Rn in the JJs prepared using TaBa2LaCu2Oy might be attributed to suppression of metallic conduction due to appreciable Ta substitution for Cu in the barrier region.