MgO/YBa 2Cu 3O 7− x multilayer thin films grown on (100) LaAlO 3 by pulsed laser deposition

Abstract

MgO/YBa 2Cu 3O 7− x (YBCO) and YBCO/MgO/YBCO multilayers were grown on (100) LaAlO 3 substrates by pulsed laser deposition. Reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and atomic force microscopy (AFM) were used to characterize the layers. Deposition of MgO on YBCO at elevated temperatures resulted in oxygen-deficient YBCO layers that did not exhibit a superconducting transition above 80 K. However, room-temperature growth of MgO on a fully oxygenated YBCO film with a transition temperature T c=90 K, preserved the oxygen and superconducting properties in the YBCO underlayer. MgO deposited at room temperature on YBCO was polycrystalline, and the YBCO overlayer was amorphous. However, crystalline YBCO overlayers were obtained when a thin SrTiO 3 buffer layer was used between the polycrystalline MgO and YBCO overlayer. Results of the microstructural characterization by RHEED and AFM showed that both the SrTiO 3 buffer and YBCO overlayer grew in the (110) orientation. XRD studies confirmed that the c-axis of the YBCO overlayer was parallel to the growth plane.