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 LaA1O₃ substrates by POMBE using a Mg(dpm)₂ precursor. MgO crystallinity, as assessed by x-ray diffraction rocking curves, improved with the use of CuO_x or YBa₂Cu₃O₇-_δ buffer layers. YBa₂Cu₃O₇-_δ films grown on the MgO layer by POMBE exhibited a T_c0of 83 K and a J_c(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 I_cR_nproduct of 52 μV at 10 K, demonstrating that sputter-induced grain boundary junctions are compatible with multilayer technology.