CONCENTRATION RANGE FOR SUPERCONDUCTIVITY IN HIGH-QUALITY PR2-XCEXCUO4-Y THIN-FILMS

We report ac susceptibility, electrical resistivity, and structural me asurements on crystalline Pr2-xCexCuO4-y, (PCCO) thin films prepared b y pulsed laser deposition. We find superconductivity occurs within a n arrow Ce concentration range (0.13<x<0.20) similar to that found for c eramic samples of this ''electron-doped'' material. Our results are qu ite different than those recently reported [Phys. Rev. Lett. 74, 4927 (1995)] on PCCO single crystals where superconductivity near 20 K was found for Ce concentration as low as x=0.04. Possible reasons for this difference will be discussed.