High-quality [100] and [110] YBa2Cu3O7-δ films for Josephson tunnelling

YBa2Cu3O7-delta/PrBa2Cu3O7-delta (YBCO/PBCO) bilayers [100] and [110] oriented are in situ grown by a reactive co-deposition technique on SrTiO3 single-crystal substrates. Atomic force microscopy and transmission electron microscopy images, X-rays diffraction patterns have been used to investigate their structural properties and surface morphology, in order to optimize their characteristics. To obtain high-quality YBCO [100] and [110] layers, we first deposit a PBCO template layer at 630degreesC, followed by a YBCO film at 630-750degreesC, with a growth rate of 0.063 nm/s. They display a very high crystallinity and a surface roughness as low as 0.5 nm for YBCO/PBCO [10 0] bilayer at a 1 mum(2) scale. Reproducible Josephson junctions have been made on these films. (C) 2002 Elsevier Science B.V. All rights reserved.