GB1360100A - Superconductive tunnelling device - Google Patents

Abstract

1360100 Superconductor devices INTERNATIONAL BUSINESS MACHINES CORP 4 Oct 1971 [31 Dec 1970] 46014/71 Heading H1K In a superconductor tunnelling (Josephson) device one of the electrodes contains an intermetallic compound. The compound is formed as a thin layer at the interface of two layers of its components one of which may be a superconductor, and inhibits hillock formation at the barrier. In a first arrangement a layer of Pb is deposited on a layer of Au so that a thin layer of intermetallic compound is formed therebetween. The Pb layer is plasma or thermally oxidized to form a tunnelling barrier and a second electrode comprising Pb or consecutive layers of Pb and Au is deposited on top of the barrier layer. Alternatively both electrodes may comprise consecutive Pb-Au-Pb layers or the first electrode may have this structure whilst the second electrode comprises a layer of Pb covered with Au. In a further arrangement two layers of intermetallic compound are provided in the first electrode by depositing layers in the sequence Au-Pb-Au-Pb and the upper electrode comprises a Pb-Au-Pb structure. The device may comprise a tunnelling cryotron formed on a substrate of silica glass, cork, mica or an oxidized ground plane. The tunnelling barrier may be of silicon oxide or lead oxide or in general oxides, sulphides or nitrides or may be a vacuum. The compound may comprise Pb with one of Au, Pd, Pt, Mg, Te and Tl, or In with one Cu, Ag, Au, Sn, Mg, Ni, and Bi. The metal layers may be deposited by vacuum evaporation or sputtering and different materials may be used in the first and second electrodes. The intermetallic compound and the remainder of the layer of compound forming material may be disposed between the superconductor electrode material and the barrier.