Fabrication of niobium SIS junctions with a magnetic tunneling barrier NiOx

We report on the fabrication of a new type of superconductor-insulator-superconductor junctions with intrinsically vanishing Josephson current. We have fabricated junctions with a tunneling barrier containing oxidized 3d transition metal Ni, i.e., Nb/NiOx/Nb and Nb/NiOx/Al/Nb stacked junctions. In the junction fabrication process, we used a conventional RIE technique called selective niobium etch process. The junction size was varied from 2.5 x 2.5 to 10 x 10 mum(2). The Josephson current of these junctions was suppressed to zero or nearly zero, while a sharp gap structure was also observed. This new-type device will be promising in realizing a highly integrated mixer. (C) 2002 Elsevier Science B.V. All rights reserved.