Surface characterization of as-grown CeO sub(2) cap layer morphology evolution and critical current density of post-deposited YBCO films

Cerium dioxide (CeO sub(2)) cap layers for high temperature superconducting coated conductors were fabricated on yttria-stabilized zirconia (YSZ) single crystal substrates via the unbalanced radio frequency (RF) magnetron sputtering method. YBa sub(2)Cu sub(3)O sub(7- delta ) (YBCO) films were epitaxially deposited on the as-grown CeO sub(2)/YSZ (001) stacks using water-free metal organic deposition (MOD) method. The surface morphology evolution of CeO sub(2) cap layers could be tuned by adjusting the sputtering pressure, from smooth and uniformly granular, to rough and composed of spindle-like islands. According to the atomic force microscopy (AFM) data, a monotonic relationship could be found between the root mean squared (RMS) roughness value and flat area fraction. The critical current density (J sub(c)) of the MOD-YBCO film varied significantly along with the CeO sub(2) morphology evolution, caused by the degradation of YBCO film's epitaxial growth. It was found that the as-grown CeO sub(2) cap layer deposited at 0.5 Pa could serve as a favorable template and did not require post-modification, on which YBCO film with J sub(c) of 1.92 MA/cm super(2) (77 K, self-field) could be obtained. The MOD process would be improved in our future study by parameter optimization to enhance the J sub(c) property of YBCO films.