Superconductivity of nanostructured Pb7Bi3 films doped by Ce

By means of electrochemical deposition from electrolytes, containing salts of Pb and Bi (0.03 mol/l and 0.02 mol/l respectively) thin films of intermetallic Pb7Bi3 have been fabricated. The superconducting transition temperature of the films was measured to be around 7.8 K. The deposition of the films with thickness of 50-100 nm was performed via passing rectangular current pulses with given amplitude and length. It was shown that adding salt of Ce into the electrolyte leads to a significant growth of the Tc for the deposited films reaching its maximum at the salt concentration of 0.06 mol/I. X-ray analysis data revealed the single phase of Pb7Bi3 films with hexagonal structure (SG) having a textures parallel to (101) plane. The morphology of the film surface is characterized by nanocluster structure with typical grain size around 70-80 nm. For the films, fabricated with adding salt of Ce, together with the intermetallic phase of Pb7Bi3, the second phase containing Bi is detected. At the same time, the typical grain size is reduced to 20-30 nm. Additionally, the suppression of the superconductivity in the grown films is investigated. The influence of the composition and structure on the superconducting critical temperature is discussed for both types of the fabricated films.