Homoepitaxial growth of low roughness SrTiO3 by pulsed laser deposition: application to YBa2Cu3O7-x -based thin films and superlattices

Abstract YBa 2 Cu 3 O 7 thin films and YBa 2 Cu 3 O 7 -based insulator/superconductor superlattices have been grown by pulsed laser deposition on homoepitaxial SrTiO 3 buffer layer. The SrTiO 3 buffer layer decreases the substrate roughness, improving the epitaxial relation of the YBa 2 Cu 3 O 7 layer or YBa 2 Cu 3 O 7 /PrBa 2 Cu 3-x Ga x O 7 superlattices with the substrare, 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 YBa 2 Cu 3 O 7 film measured by atomic force microscopy. The X-ray diffraction patterns recorded from YBa 2 Cu 3 O 7 /SrTiO 3 superlattice structures show only ±1 satelite around the (100) reflection line. The poor quality of the superlattice is attributed to the SrTiO 3 regrowth mechanisms over YBa 2 Cu 3 O 7 which develop a high roughness into the YBa 2 Cu 3 O 7 /SrTiO 3 inverse interface, although the SIMS in-depth profiles show a perfect chemical periodicity while the growth temperature is lower than 710°C.