Preparation of YBa2Cu3O7-δ and La1.85Sr0.15 CuO4 Bilayer Structure for Superconducting Connection

To connect superconducting wires through a different superconductor, it is essential to evaluate a range of characteristics of the various superconducting materials. In this study, a combination of YBa
₂
Cu
₃
O
_7-δ
(YBCO) and La
_1.85
Sr
_0.15
CuO
₄
(LSCO), which are typical high-temperature superconductors, was investigated. An LSCO/YBCO layered thin film (LSCO/YBCO bilayer) was prepared and its crystallinity, surface morphology, and electrical properties were evaluated. The LSCO thin film grew epitaxially, oriented to the (00l) plane on the (00l)-oriented YBCO thin film due to the small lattice mismatch between YBCO and LSCO. The surface flatness of the LSCO/YBCO bilayer was almost the same as that of the LSCO thin film, because the LSCO thin film grew without roughening the surface of the YBCO thin film. The electrical resistivity of the LSCO/YBCO bilayer decreased at the individual superconducting-transition temperatures of YBCO and LSCO, and eventually became superconducting at 20 K. The superconducting properties of YBCO and LSCO were almost preserved, with the result that a superconducting connection between YBCO and LSCO was achieved.