Study and preparation of high Tc superconducting (HTSC) thin films for electronic applications

High-quality superconducting YBa₂Cu₃O_7-x thin films were reproducibly prepared by thermal coevaporation of BaF₂, Y, and Cu. Uniformity in thickness and composition of the deposited films can be achieved for a 2.5-in-diameter area on the substrate holder. Four-probe resistivity, critical current measurements, and X-ray diffraction were used to characterize the films after a postdeposition annealing in a mixture of O₂ and H₂O. Highly c -oriented films with total transition temperature above 90 K were reproducibly fabricated on (001) SrTiO₃ with a critical current of 4×10⁴ A/cm² at 77 K. The total transition temperatures of films fabricated on ZrO₂, (001) YAG, (001) MgO, and (001) MgAl₂O₄ were 87 K, 74 K, 63 K, and 57 K, respectively. The effect of the postdeposition processing ambient on the preparation of the thin films was studied. The role of H₂O vapor and of an HF getter (e.g. SiO₂) during the high-temperature anneal is understood through a thermodynamic analysis of the fluorine-removal reaction. Photolithography and argon ion milling have been used to produce YBa₂Cu₃O_7-x wires from several micrometers to submicrometer in size. The wires behaved as scaled-down bulk superconducting films rather than weak links