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

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.