Intermediate normal metal layers in superconducting circuitry

Abstract

A thin, nominally 150 angstroms, normal metal layer, nominally the noble normal metal palladium, sandwiched intermediate between two superconducting layers, nominally niobium, supports totally superconducting current flow therethrough such normal metal layer by the quantum mechanical tunneling effect. Such a thin normal metal layer is useful as a stop etch layer for fabrication process control, including especially the selective niobium anodization process, as an oxidation resistant or immune layer to which totally superconducting electrical contact may be reliably made such as by soldering, and as a patterned resistor in those regions of the substrate plane where such thin normal metal layer is not sandwiched by superconducting layers. Particularly concerning such stop etch function, a thin normal layer of palladium will serve as a stop etch layer to the etching of niobium while not precluding totally superconducting contact therethrough such thin palladium layer. Particularly concerning the electrical contact function, a superconducting wire, nominally niobium, may be soldered with lead-tin or indium-tin to a thin normal metal layer of palladium in the formation of a totally superconducting connection therethrough such thin palladium layer. Particularly concerning such patterned resistor, terminus superconducting sandwiches of niobium-thin palladium-niobium may be electrically resistively interconnected by such thin palladium layer precisely patterned in the region(s) wherein it is not sandwiched, only such unsandwiched region(s) of such thin palladium layer contributing controllably determinable resistance to the interconnection(s).