FABRICATION AND CHARACTERISTICS OF ALL YBCO SANDWICH-TYPE JUNCTIONS USING HIGHLY CRYSTALLINE DC SPUTTERED SUPERCONDUCTING A-AXIS ORIENTED Y1BA2CU3O7-X FILMS

We report on the fabrication and characteristics of sandwich-type tunnel junctions with highly crystalline sputtered a-axis oriented thin film of Y1Ba2Cu3O7-x (YBC) as the base and the counter electrode. The junctions have been fabricated on SrTiO3 (100) and MgO (100) substrates. A non-superconducting phase of YBC corresponding to a lattice constant of approximately 4.08 angstrom is used as the barrier layer making this an all YBC sandwich junction. For all temperatures below T(ce)(R = 0) of the device, a zero voltage current was observed. The critical current density (J(c)) of the device was found to be dependent on the thickness of the barrier layer and the crystallinity of the a-axis oriented YBC electrodes. Al 40 K. such a junction fabricated on a SrTiO3 (100) substrate was found to have a J(c) of approximately 1.8 x 10(4) A/cm2 and an I(c)R(n) product of approximately 0.2 mV.