Tunneling measurements on superconductor/insulator/superconductor junctions using single-crystal YBa2Cu3O7-x thin films.

We have, for the first time, made quasi-particle tunneling measurements on a YBa2Cu3O7-x(001)/Y2O3 (001)/YBa2 Cu3 O7-x (001)junction, which was epitaxially grown on a MgO(100) substrate in an in-situ process. Both layers of YBa2 Cu3 O7-x showed the same superconducting transition of Tc end =86 K with ΔT(R=10–90%)=1.5 K. Quasi-particle tunneling in the direction perpendicular to the Cu-O planes was measured. A gap parameter Δ(4.5 K) of 9.0±0.2 meV and a value of 2Δ/kTc of 3.5+0.4-0.6 were obtained. [ABSTRACT FROM AUTHOR]