Sequential Ar-O2 sputtering of Y2O3, BaF2, and CuO targets for preparation of Y-Ba-Cu-O superconducting films without wet-O2 annealing

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Abstract
Superconducting Y‐Ba‐Cu‐O (YBCO) films have been prepared by ex situ O2 annealing of multilayer films deposited on yttria‐stabilized zirconia substrates by sequential rf diode sputtering of Y2O3, BaF2, and CuO targets, all of which are chemically stable. If sputtering is performed in an Ar ambient, the as‐deposited films contain sufficient F to require its removal by annealing in wet O2 at about 800 °C or above before the superconducting YBCO phase can be formed by annealing in dry O2. However, sputtering in an Ar‐O2 ambient greatly reduces the F content, making it possible to obtain the superconducting phase by annealing in dry O2 only. If the ambient contains about 20% O2, films with Tc (R=0)>85 K can be prepared without wet‐O2 annealing. The Ar‐O2 process therefore has the potential for in situ preparation of superconducting YBCO films.