Preparation of superconducting oxide films from metal trifluoroacetate solution precursors

Abstract

Superconducting thin films of Y1Ba2Cu3O7-δ have been prepared on single-crystal yttria-stabilized zirconia (YSZ) and SrTiO3 substrates using metal trifluoroacetate spin-on precursors. The films exhibit resistive transition widths of 1.5-1.7 K with zero resistance at temperatures as high as 91-94 K. The superconducting phase is formed by first decomposing the trifluroacetate film to the fluorides and then converting the fluorides by reaction with water vapor. The properties of the films prepared on YSZ substrates depend on the amount of conversion of the fluorides by reaction with water. Films which show the presence of some unreacted barium fluoride have strong c-axis normal preferred orientation, with a sharp resistive transition. When all the barium fluoride is converted, the films are more randomly oriented, and have a broader transition to zero resistance. Films prepared on SrTiO3 show different preferential growth directions depending on substrate orientation. Unlike films grown on YSZ substrates, these films exhibit the best superconducting properties when all the fluoride phases in the films are converted.