Preparation of superconducting thin films of calcium strontium bismuth copper oxides by coevaporation

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Abstract
Superconducting films of Ca‐Sr‐Bi‐Cu oxides have been prepared by coevaporation of CaF2, SrF2, Bi, and Cu, followed by post‐oxidation in wet O2. The films were characterized by four‐probe resistivity measurements, Rutherford backscattering, transmission electron microscopy, x‐ray diffraction, and Hall measurements. Zero resistance was achieved at ∼80 K, although evidence of traces of superconductivity at higher temperatures was seen in resistivity and Hall data. The critical current at 4.2 K was 1.0×106 A cm−2. The films were epitaxial on 〈100〉 and 〈110〉 SrTiO3 substrates. The electrical and structural properties of the films were insensitive to film composition over a wide range of stoichiometries.