AbstractAn important class of electronic devices could be realized with current state-of-the-art high-Tc superconductor (HTSC) thin films if a method were found for the formation of multilevel structures separated by thin dielectric layers. It has been found that such structures can be formed with tantalum oxide as the spacer layer because of its high melting point (1870°C) and good chemical stability at the high temperatures commonly used to anneal thin films of YBaCuO superconductor. Good results have been achieved with thin films prepared by electron beam (EB) sequential deposition from Y, BaF2 and Cu targets onto oriented (100) strontium titanate substrates and oxygen furnace annealing at 850°C to promote the epitaxial alignment and growth of the superconducting crystalline phase. Two-layer structures have been formed by interposing a tantalum oxide barrier deposited by EB evaporation between two successive layers of HTSC films. The transition temperatures of both layers were checked by resistance measurements and found to display superconductivity after annealing. However, the top (second) layer was found to always show a reduced abruptness of the transition characteristic thereby indicating, perhaps, a lesser degree of epitaxial alignment since it makes no direct contact with the substrate surface.
Magnetic field dependence of Josephson photoresponse in high-Tc superconductor thin films