HOMOEPITAXIAL GROWTH OF LOW ROUGHNESS SRTIO3 BY PULSED-LASER DEPOSITION - APPLICATION TO YBA2CU3O7-X-BASED THIN-FILMS AND SUPERLATTICES

YBa2Cu3O7 thin films and YBa2Cu3O7-based insulator/superconductor superlattices have been grown by pulsed laser deposition on homoepitaxial SrTiO3 buffer layer. The SrTiO3 buffer layer decreases the substrate roughness, improving the epitaxial relation of the YBa2Cu3O7 layer or YBa2Cu3O7/PrBa2Cu3-xGaxO7 superlattices with the substrate, as shown by Rutherford backscattering spectrometry in channelled geometry and RHEED analyses performed at the end of the growth. However, this does not result in a significant smoothness improvement of the YBa2Cu3O7 film measured by atomic force microscopy. The X-ray diffraction patterns recorded from YBa2Cu3O7/SrTiO3 superlattice structures show only +/-1 satellite around the (100) reflection line. The poor quality of the superlattice is attributed to the SrTiO3 regrowth mechanisms over YBa2Cu3O7 which develop a high roughness into the YBa2Cu3O7/SrTiO3 inverse interface, although the SIMS in-depth profiles show a perfect chemical periodicity while the growth temperature is lower than 710-degrees-C.