SUPERCONDUCTING AND STRUCTURAL-PROPERTIES OF ND2-XCEXCUO4-Y THIN-FILMS ON PEROVSKITE AND FLUORITE SUBSTRATES

High quality epitaxial Nd2-xCeCuO4-y (NCCO) thin films were fabricated on various substrates by pulsed-laser deposition using N2O reactive gas. The similarities and dissimilarities of the superconducting and structural properties of NCCO films, on perovskite-type substrates such as LaAlO3, NdGaO3, and SrTiO3 and on a fluorite-type substrate of yttria-stabilized zirconia (YSZ), were investigated systematically as a function of film thickness by transport measurements and structural analysis. A remarkable reduction of T(c) was observed when the film was thinner than a critical thickness, which strongly depends on the substrate. The critical thicknesses for which T(c) is 80% of T(c max) are 1200, 1000, 600, and 450 angstrom for LaAlO3, NdGaO3, SrTiO3, and YSZ, respectively. YSZ turns out to be the best candidate for the growth of very thin NCCO films among the substrates studied. These results show a strong correlation between the strain and T(c) in NCCO thin films and point the way to the fabrication of n-type superconducting electric field devices using ultrathin NCCO films.