Biepitaxial Josephson junctions with high critical current density based on YBa₂Cu₃O_7−δ films on silicon on sapphire Available to Purchase

High‐current‐density Josephson junctions have been produced in high‐temperature superconducting YBa₂Cu₃O_7−δ films deposited on silicon on sapphire and using biepitaxial grain boundaries. The technique is estimated to be useful in integrating superconducting and semiconducting components. A multilayer system of epitaxially grown films was used to form the junctions. A double buffer layer CeO₂/ZrO₂(9.5% Y₂O₃) prevented interactions between YBa₂Cu₃O_7−δ and Si during the high‐temperature deposition and promoted formation microcrack‐free films with a critical current density of 2×10⁶ A/cm² at 77 K. A MgO seed layer, with (001)MgO∥(001)CeO₂ orientation, was used to induce a 45° crystallographic grain boundary in YBa₂Cu₃O_7−δ at its edge. An additional epitaxial buffer double layer of YBa₂Cu₃O_7−δ and SrTiO₃ on top of the seed layer promoted the formation of a grain boundary of better crystallinity and stoichiometry. It improved the critical current of the junction about tenfold and resulted in characteristic I_cRn products of 150 μV at 77 K in microbridges crossing the grain boundary. Microwave‐induced steps were detected at 77 K up to voltages corresponding to the characteristic I_cRn value. Peak‐to‐peak responses to superconducting quantum interference devices reached values of 7 μV at 77 K.