X‐ray photoelectron spectroscopy analysis of Y‐Ba‐Cu‐O surface barrier for superconducting junctions

Fabrication of junctions with a Y‐Ba‐Cu‐O/barrier/Y‐Ba‐Cu‐O trilayered structure is attempted. The barrier layer is formed by CF4 plasma treatment. A nonlinear structure is observed in the current‐voltage curve of the junction, but the Josephson current is not detected. The Y‐Ba‐Cu‐O films before and after CF4 plasma treatment are investigated by x‐ray photoelectron spectroscopy to clarify the junction’s structure. Compositional deviation is detected at the surface layer of the Y‐Ba‐Cu‐O films. Of the CF4 plasma treatment effects, fluorination of yttrium and reduction of copper are observed.