Electrical contact to superconductors

Electrical contacts to conventional superconductors and high-critical-temperature oxide superconductors are reviewed. The technologically important conventional superconductors considered are Nb and its alloys and compounds, the oxide superconductors are typified by YBa/sub 2/Cu/sub 3/O/sub 7/. Three distinct forms in which the superconductor can be fabricated are considered: thin films for electronics applications, multifilamentary wires for magnets and large-scale applications, and monofilaments or tapes for measurements of the current-carrying capability of a superconducting material. It is concluded that electrical contact to conventional superconductors is relatively straightforward. However, contacting the high-temperature oxide superconductors is difficult not only because the characteristic lengths are short, 0.1 to 10 nm, but because they are strongly dependent on crystal orientation and the oxides tend to be chemically unstable within that distance of the surface.<>