Analysis of Electrical Characteristics and Magnetic FieldDependencies of YBCO Step Edge and Bi-crystal GrainBoundary Junctions for rf-SQUID Applications

摘要

The dc characteristics and magnetic field dependencies of Yba-Cu-O bicrystal grain boundary junctions (BGBJs) and step edgejunctions (SEJs) were investigated for fabrication of rf-SQUIDs. Testjunctions with up to 8 μm widths as well as the junctions of the two typesjunction based rf-SQUIDs were studied. The SEJs typically showed lowerJc and higher ρN as compared to the BGBJs, resulting in close IcRNproducts. All the BGBJs showed classical field dependent Ic followingtheir junction width, resembling Fraunhofer-patterns. The field sensitivityof the BGBJs' Ic led to low yield submicron BGBJ rf-SQUIDs partiallyimpaired by the earth magnetic field. Two major behaviours of low andhigh field dependencies of Ic were observed for the SEJs. Only the lowfield-sensitive SEJs resulted in micron size junction rf-SQUIDs notimpaired by the earth magnetic field. The low field-sensitive SEJs led tolow 1/f noise magnetically stable rf-SQUIDs proper for applications inunshielded environments at 77 K.