International Business Machines Corporation

Frank Lichtenberg

Jochen D Mannhart

Darrell G Schlom

These superconducting circuit elements, namely SNS heterostructures, such as, e.g. Josephson junctions and field-effect transistors, have a sandwich structure consisting of at least one layer of high-T.sub.c superconductor material arranged adjacent to a metallic substrate, possibly with an insulating layer in between, the substrate, the superconductor and--if present--the insulator all consisting of materials having at least approximately matching molecular structures and lattice constants. Electrical contacts, such as source, drain and gate electrodes are attached to the superconductor layer and to the substrate, respectively. The electrically conductive substrate consists of a metallic oxide such as strontium ruthenate Sr.sub.2 RuO.sub.4, whereas the superconductor layer is of the copper oxide type and may be YBa.sub.2 Cu.sub.3 O.sub.7-.delta., for example. The insulator layer (10) may consist of SrTiO.sub.3. The manufacture of these devices starts with the preparation of the substrate material from a 2:1,1 molar ratio of SrCO.sub.3 to RuO.sub.2 and involves a floating zone melting process yielding single crystals of the strontium ruthenate Sr.sub.2 RuO.sub.4 material onto whose (001) surface the superconductor layer as well as the barrier layer can be epitaxially deposited.

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Adliswil, Switzerland

Frank Lichtenberg