Orientation effects in YBCO/PBCO/YBCO trilayer junctions

We have completed a comparative study on YBaCuO/PrBaCuO/YBaCuO trilayer junctions according to the crystallographic orientation of the films used in order to determine the best orientation to get a Josephson junction working at 77 K. To this end, 100% a-axis, [110] and [103] oriented samples have been deposited using the hollow cathode method. In order to characterize our junctions, /spl Phi/ scan, resistivity and electrical measurements were made, None of the a-axis junctions were able to work above 20 K, due to the very large resistive transition of the base electrode. On the other hand, the structures made with [110] films had good superconducting properties and the barrier exhibited superconducting transition beyond 80 K (J/sub c/(77 K)/spl ap/5.10/sup 3/ A/cm/sup 2/), but no Josephson effects were seen, Finally, we would stress the fact that almost all the devices made with [103] oriented films exhibited clear Shapiro steps at 77 K. The T/sub c/ and J/sub c/(77 K) of these structures were respectively 82 K and 2.102 A/c cm/sup 2/.