EFFECT OF SUBSTRATE MATERIALS ON LASER-DEPOSITED ND1.85CE0.15CUO4-Y FILMS

The growth morphology and interface structure of Nd1.85Ce0.15CuO4-y (N CCO) films grown by pulsed laser deposition on two different types of substrates, ''perovskite'' LaAlO3 (LAO) and SrTiO3 (STO) and ''fluorit e'' Y2O3-stabilized ZrO2 (YSZ), were studied using cross-sectional ele ctron microscopy. Structurally, the NCCO films are different when grow n on the two types of substrates in three aspects: (i) epitaxy, (ii) s ubstrate-film intermixing, and (iii) substrate-film interface roughnes s. In general, films deposited on ''fluorite'' substrates showed bette r superconducting properties than the films grown on ''perovskite'' su bstrates, especially for thinner films. Lattice mismatch consideration s are not sufficient to explain the observed differences since films g rown on the YSZ substrate showed sharp substrate-film interface in spi te of their large lattice misfit. The atomic arrangements at the inter face were analyzed in terms of electrostatic energy (charge balance) a nd matching of the oxygen sublattices in order to account for the expe rimental results.