Properties of YBa2Cu3O7 thin films deposited on substrates and bicrystals with vicinal offcut and realization of high IcRn junctions

The surface morphology, microstructure and transport properties of epitaxia l YBa2Cu3O7 and PrBa2Cu3O7 thin films and heterostructures deposited on sli ghtly vicinal substrates of SrTiO3 by high pressure oxygen sputtering were studied. The vicinal angles of the substrates and bicrystals were less then 13 degrees. Depending on the tilt angle of the substrate a transition from spiral or island to step-flow growth leading to an improvement of the surf ace roughness was observed. Atomic force and transmission electron microsco py were used for these investigations. Furthermore, electrical and structur al properties of YBa2Cu3O7 thin films on vicinal offcut SrTiO3 bicrystals w ith different grain boundary types were studied. This included junctions wi th a 2x 12 degrees tilt or twist of the YBa2Cu3O7 c-axis across the grain b oundary. In comparison to conventional [001]-tilt grain boundaries bicrysta l Josephson junctions [100]-tilt grain boundaries showed high I-c R-n -prod ucts of up to 1.2 meV at 77 K and up to 8 meV at 4.2 K. IV-curve instabilit ies, probably of magnetic origin due to flux flow in the electrodes, often could he observed for junctions biased with high current densities.