Improving the Josephson energy in high-Tc superconducting junctions for ultra-fast electronics.

We report the electrical transport of thin vertically-stacked Josephson tunnel junctions. The devices were fabricated using 16 nm thick GdBa2Cu3O7-δ electrodes and 1-4 nm SrTiO3 as an insulating barrier. The results show Josephson coupling for junctions with SrTiO3 barriers of 1 and 2 nm. Subtracting the residual current in the Fraunhofer patterns, energies of 3.1 mV and 5.7 mV at 12 K are obtained for STO barriers of 1 nm and 2 nm, respectively. The residual current may be related to the contribution of pinholes and thickness fluctuations in the STO barrier. These values are promising for reducing the influence of thermal noise and increasing the frequency operation rate in superconducting devices using high-temperature superconductors.