The effect of substrate-off-cut on the properties of epitaxial thin films of YBa Cu O 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 08 and 68 in steps of 18. RBS angular scans demonstrate the high degree of alignment between thew100xdirection of the substrate and the c-axis of the films at all angles, and minimum yield values, xmin, between 3 and 5% confirm the good crystallinity throughout the series. STM-images reveal significant changes in the surface morphology of the YBCO-films with increasing vicinal angle, the film deposited onto the 18 substrate showing the smoothest surface. The analysis of the critical current densities from VSM-measurements indicates an overall trend towards decreasing current densities with increasing vicinal off-cut at 4.2 K but increasing at 77 K. We interpret this as a change in the dominant trapping regimes at high and low temperature. Pre-annealing the substrates in flowing oxygen results in a visible vicinal step-structure on the surface of the substrates which may enable closer control of the microstructure of such films. q1998 Elsevier Science B.V.