ORIENTATION EFFECTS IN YBCO PBCO/YBCO TRILAYER JUNCTIONS/

We have completed a comparative study on YBaCuO/PrBaCuO/YBaCuCO trilay er junctions according to the crystallographic orientation of the film s used in order to determine the best orientation to get a Josephson j unction working at 77 K. To this end, 100% a-axis, [110] and [103] ori ented samples have been deposited using the hollow cathode method, In order to characterize our junctions, Phi scan, resistivity and electri cal 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 bas e electrode, On the other hand, the structures made with [110] films h ad good superconducting properties and the barrier exhibited a superco nducting transition beyond 80 K (J(c)(77 K) approximate to 5.10(3) A/c m(2)), but no Josephson effects were seen, Finally, we would stress th e fact that almost all the devices made with [103] oriented films exhi bited clear Shapiro steps at 77 K. The T-c and J(c)(77 K) of these str uctures were respectively 82 K and 2.10(2) A/cm(2).