A Comparative Study of Different Tunnel Barriers for C-Axis Oriented Y(Ho)Ba2Cu3O7 Based Trilayer Structures

Abstract

We report on the structural and electrical characterization of c-axis oriented Y(Ho)Ba2Ca3O7 -based trilayer structures with different insulating layers. A comparative study of Y2O3 , SrTiO3 and PrBa2Cu3O7 barriers is carried out. Structural characterization demonstrates the epitaxial growth of the heterostructures with sharp interfaces between the different layers. Resistivity and ac susceptibility dependences on temperature indicate no degradation of the superconducting properties of the bottom and top electrodes. Josephson effect and quasi-particle tunneling are observed in the YBa2Cu3O7/Y2O3/YBa2Cu3O7 structures. The best conductance characteristics are obtained for YBa2Cu3O7/PrBa2Cu3O7/HoBa2Cu3O7 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 normal state value are measured in these junctions.