YBa2Cu3O7−δ on MgO films grown by pulsed organometallic beam epitaxy and a grain boundary junction application

MgO films and YBa2Cu3O7−δ/MgO multilayer films were developed with the pulsed organometallic beam epitaxy (POMBE) growth technique, and grain boundary junctions were fabricated from the films to demonstrate the utility of the multilayers. High-quality MgO films were grown on LaAlO3 substrates by POMBE using a Mg(dpm)2 precursor. MgO crystallinity, as assessed by x-ray diffraction rocking curves, improved with the use of CuOx or YBa2Cu3O7−δ buffer layers. YBa2Cu3O7−δ films grown on the MgO layer by POMBE exhibited a Tc0 of 83 K and a Jc (12 K) exceeding 106 A/cm2 for applied magnetic fields up to 3 × 104 G. Grain boundary junctions were formed by growing YBa2Cu3O7−δ on MgO films that had been pretreated with a simple sputtering technique. This sputtering induces a controlled, 45°grain boundary in subsequently deposited YBa2Cu3O7−δ films. The resulting boundary showed weak-link current-voltage behavior and an IcRn product of 52 μV at 10 K, demonstrating that sputter-induced grain boundary junctions are compatible with multilayer technology.