Characterization of Nb/AlOx-Al/Nb Josephson junctions by anodization profiles

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Abstract
The thin tunneling barrier in a Nb/AlOx‐Al/Nb Josephson junction was characterized by anodization profiles. Our studies focused on Nb/AlOx and Al/Nb interfaces in Nb/AlOx‐Al/Nb junctions made by varying certain process parameters. The interface quality was checked by the anodization profiles and was greatly affected by film thickness, layer sequence, annealing treatment, and the existence of a thin oxide. By comparing the profiles with the junction characteristics measured at 4.2 K, we confirmed that the interface sharpness in the profiles is related to the junction quality. The anodization profile is a useful tool to diagnose the tunneling barrier interfaces in Nb/AlOx‐Al/Nb Josephson junctions, especially at room temperature during fabrication.