Preparation and properties of YBCO/Bi-2212/YBCO superconducting trilayer films by acetate based sol–gel method

Abstract

YBa2Cu3O7−δ(YBCO)/Bi2Sr2CaCu2O8+δ(Bi-2212)/YBCO trilayer films with c-axis epitaxial orientation have been successfully prepared on LaAlO3 (LAO) monocrystalline substrates by sol–gel method using metallic acetates as starting materials. The effect of heat treatment temperature of upper YBCO films on the structure and superconductivity of YBCO/Bi-2212/YBCO planar-type junction have been studied. When the upper YBCO film fabricated at 750 °C, YBCO/Bi-2212/YBCO trilayer films exhibited good in-plane and out-of-plane growth texture and good superconductivity. Two superconducting transition steps in the R–T curves of YBCO/Bi-2212/YBCO trilayer films were clearly observed. Current–voltage (I–V) curves at 50–65 K of trilayer structure exhibit a supercurrent with zero voltage, and the superconducting critical current Ic is proportion to (1 − T⁄Tc)3.5. We suggest that a weak-link contact, which appears to have an SNSNS type structure, formed at the interface of YBCO/Bi-2212/YBCO trilayer structure.