Josephson Admittance Spectroscopy of Log-Periodic Antenna at the Submillimeter Wavelength Range

Application of Josephson admittance spectroscopy for the spectral analysis of a broad-band log-periodic antenna was demonstrated at the frequency range from 50 to 700 GHz. A real part of the antenna admittance was reconstructed as a function of the frequency, when the antenna was connected to a Josephson junction. Small-scale features were observed on this dependence. They demonstrated a periodicity in the logarithmic frequency scale and were related to the antenna resonances

Evolution of electrical and electrodynamic properties of YBa2Cu3O7-x bicrystal Josephson junctions with oxygen loading

The IV-curves and dynamic resistances R-d(V) of [001]-tilt YBa2Cu3O7-x bicrystal Josephson junctions have been experimentally studied at various levels of oxygen loading. Oxygen content was modified by annealing in ozone atmosphere, in vacuum or in air. Deviations of the IV-curves from those predicted by the RSJC model in the form of additional nonlinearities at the middle and high voltages were found to decrease after enhancement of oxygen content in junctions. Electrodynamic properties of Josephson junctions were analyzed using log-periodic YBa2Cu3O7-x antennas, integrated with the junctions. Fine structures on the IV-curves, related to antenna resonances, were modified with oxygen content due to better antenna-junction coupling and lower electromagnetic losses in YBa2Cu3O7-x film

Trimming of high-Tc bicrystal Josephson junctions by ozone and vacuum annealing

AbstractSpecific 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 90K 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 IcRnvalues 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