Orientation effects in YBCO/PBCO/YBCO trilayer junctions

We have completed a comparative study on YBaCuO/PrBaCuO/YBaCuCO 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, 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 a superconducting transition beyond 80 K (J(c)(77 K) approximate to 5.10(3) A/cm(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-c and J(c)(77 K) of these structures were respectively 82 K and 2.10(2) A/cm(2).