Novel all-high Tc epitaxial Josephson junction

Josephson junctions are essential components in high‐temperature superconductive integrated circuits. YBaCuO/Nb‐doped SrTiO3/YBaCuO epitaxial Josephson junctions have been designed, fabricated, and tested. The YBaCuO and Nb‐doped SrTiO3 films were deposited by off‐axis sputtering. Both dc and ac Josephson effects have been observed and the supercurrent persists up to 80 K. The critical current density is an exponential function of the barrier layer thickness. The product of critical current and normal resistance is between one and three millivolts. A superconducting quantum interference device made of the junctions displays magnetic field modulation of critical current.