Trimming of High-Tc Bicrystal Josephson Junctions by Ozone and Vacuum Annealing

Abstract Specific values of characteristic voltages IcRn and normal-state resistances Rn of high- Tc Josephson junctions (JJ) are often required for their THz applications in detection and spectroscopy. Recently, evolution of these electrical parameters of [001]-tilt YBa2Cu3O7-x bicrystal JJ after low-temperature ozone annealing has been studied. Here, we present the effect of ozone and vacuum annealing on the IV -curves of [100]-tilt YBa2Cu3O7-x bicrystal JJ. Annealing temperature Ta was varied from 100 °C to 225 °C. It was demonstrated, that annealing in ozone-oxygen mixture and in vacuum has an opposite effect on JJ parameters, and the changes were reversible at Ta up to 145 °C. Ozone annealing at Ta =100 °C resulted in up to 1.5 times decrease of Rn . After annealing in vacuum at higher Ta , a transition temperature Tc of JJ electrodes was reduced from 90 K to 52K, and significant, multifold changes of IcRn and Rn were observed. Further annealing in ozone at Ta up to 225 °C restored Tc and Rn almost to their initial values, but IcRn values couldn’t be increased above 20% of the initial value. The obtained results can be used for trimming of junction parameters after main fabrication procedure.