THE EFFECT OF SUBSTRATE-OFF-CUT ON THE PROPERTIES OF EPITAXIAL THIN-FILMS OF YBA2CU3O7-DELTA GROWN BY PULSED-LASER DEPOSITION

We have investigated the properties of a series of YBCO thin films of 230 nm thickness deposited onto SrTiO3 substrates (001) with a vicinal off-cut angle between 0 degrees and 6 degrees in steps of 1 degrees. RBS angular scans demonstrate the high degree of alignment between the [100] direction of the substrate and the c-axis of the films at all a ngles, and minimum yield values, chi(min), between 3 and 5% confirm th e good crystallinity throughout the series. STM-images reveal signific ant changes in the surface morphology of the YBCO-films with increasin g vicinal angle, the film deposited onto the 1 degrees substrate showi ng the smoothest surface. The analysis of the critical current densiti es from VSM-measurements indicates an overall trend towards decreasing current densities with increasing vicinal off-cut at 4.2 K but increa sing at 77 K. We interpret this as a change in the dominant trapping r egimes at high and low temperature. Pre-annealing the substrates in fl owing oxygen results in a visible vicinal step-structure on the surfac e of the substrates which may enable closer control of the microstruct ure of such films. (C) 1998 Elsevier Science B.V.