GLANCING INCIDENCE X-RAY CHARACTERIZATION OF ULTRATHIN YBA2CU3O7-X FILMS FABRICATED BY MODULATED MAGNETRON SPUTTERING

In high-T-c superconductor ultrathin films and multilayers the superco nducting current flow is extremely sensitive to the structural quality of the interfaces and to any surface irregularities. In this work we present a microstructural and morphological study of ultrathin YBa2Cu3 O7-delta (YBCO) films grown on SrTiO3 substrate. The firms (thickness <25 nm) are fabricated by magnetron sputtering with a modified process that arrows a higher grain cohesion and lower surface roughness. The analyses are performed by using high-angle single crystal diffraction, low-angle specular reflectivity and atomic force microscopy. The pres ence of distinct Kiessig fringes in the specular reflectivity spectra indicates well-defined layer-substrate and layer-air interfaces. Moreo ver, a surface roughness of about one unit cell is determined. Finally , no correlation of the substrate and surface interfaces across the la yer is found.