Abstract:
A technological route for manufacturing tunnel superconductor structures using liquid selective etching of aluminum to break the electrical contact along the lower layer of a three-layer tunnel structure and form a bridge suspended above the substrate surface is proposed and tested. It is demonstrated that, according to the proposed technological route, the formation of a three-layer structure can be performed by all methods of film deposition, including magnetron sputtering, and not only by thermal sputtering, as was done previously. Samples with Al/AlO$_x$/Nb tunnel junctions were manufactured to test the technology. The manufactured structures were measured at temperatures down to 2.8 K, the ratio of the differential resistance in the zero voltage region to the normal resistance reaches 12. The tunnel structures superconductor – insulator – normal metal – insulator – superconductor are studied, where palladium is used as a normal metal. The problem of the negative effect of palladium on aluminum-based tunnel barriers is studied and methods for solving this problem are proposed.
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