Characterization of La-doped YBCO superconducting films deposited by DC magnetron sputtering at various off-axis geometries

摘要

La-doped YBCO (Y_0.9La_0.2Ba_1.9Cu₃O _y ) superconducting films were deposited by an off-axis DC magnetron sputtering method. We investigated the relationship between the film characteristics and the deposition conditions, and drew systematical maps in terms of composition, surface morphology, crystal structure and superconducting properties for the films deposited at various spatial geometries of a substrate and a target. Correspondence between the Cu content and the surface morphology was clearly observed. Cu-rich films had precipitates on the surface. Slightly Cu-poor films exhibited c -axis orientation and a high T _c of 87 K. Among them, the film deposited at a rather fast deposition rate exhibited a flat surface with an average surface roughness R _a less than 1 nm for an area of 10 micron square. Considerably Cu-poor films contained a -axis oriented grains or exhibited very rough surfaces. The cationic ratio of Y:La:Ba did not change significantly.