A COMPARATIVE-STUDY OF DIFFERENT TUNNEL BARRIERS FOR C-AXIS ORIENTED Y(HO)BA2CU3O7 BASED TRILAYER STRUCTURES

We report on the structural and electrical characterization of c-axis oriented Y(Ho)Ba2Ca3O7-based trilayer structures with different insula ting layers. A comparative study of Y2O3, SrTiO3 and PrBa2Cu3O7 barrie rs is carried out. Structural char acterization demonstrates the epita xial growth of the heterostructures with sharp interfaces between the different layers. Resistivity and ac susceptibility dependences on tem perature indicate no degradation of the superconducting properties of the bottom and top electrodes. Josephson effect and quasi-particle tun neling are observed in the YBa2Cu3O7/Y2O3/YBa2Cu3O7 structures. The be st conductance characteristics are obtained for YBa2Cu3O7/PrBa2Cu3O7/H oBa2Cu3O7 trilayers that show quasi-ideal S-I-S behavior. Well defined maxima at +/-45 mV and a zero-bias conductance less than 5% of the no rmal state value are measured in these junctions.