Conductus, Inc.

Other

Leland Stanford Junior University

Kookrin Char

Nathan Newman

Theodore H Geballe

Aharon Kapitulnik

Robert H Hammond

Stephen M Garrison

Gregory G Zaharchuk

Mark Lee

Brian H Moeckly

Byungdu Oh

Malcolm R Beasley

Roger W Barton

John M Rowell

Stephen S Laderman

Michio Naito

Andy Kent

Ann F Marshall

A conductor suitable for use in oxide-based electronic devices and circuits is disclosed. Metallic oxides having the general composition AMO.sub.3, where A is a rare or alkaline earth or an alloy of rare or alkaline earth elements, and M is a transition metal, exhibit metallic behavior and are compatible with high temperature ceramic processing. Other useful metallic oxides have compositions (A.sub.1-x A'.sub.x)A'.sub.2 (M.sub.1-y M'.sub.y).sub.3 O.sub.7-.delta. or (A.sub.1-x A'.sub.x).sub.m (M.sub.1-y M'.sub.y).sub.n O.sub.2m+n, where 0.ltoreq.x, y.ltoreq.1 and 0.5.ltoreq.m, n.ltoreq.3, A and A' are rare or alkaline earths, or alloys of rare or alkaline earths, A' and A' are alkaline earth elements, alloys of alkaline earth elements, rare earth elements, alloys of rare earth elements, or alloys of alkaline earth and rare earth elements, and M and M' are transition metal elements or alloys of transition metal elements. The metallic oxides grow epitaxially on oxide superconductors as well as on substrates and buffer layers commonly used for growth of oxide superconductors. The oxide superconductors can also be grown epitaxially on these metallic oxides. Vastly improved performance of superconductor-normal-superconductor (SNS) junctions in high temperature superconductor materials are obtained when the normal material is a metallic oxide of the type disclosed. In the preferred embodiment, the conducting oxide CaRuO.sub.3 is used as the normal material in an SNS junelion with YBa.sub.2 Cu.sub.3 O.sub.7-.delta. as superconductor. A dc superconducting quantum interference device (SQUID) functioning at 77K fabricated with this type of junction exhibits large modulation and low noise.

Barrier layers for oxide superconductor devices and circuits

A novel method of producing weak-link grain boundary Josephson junctions in high temperature superconducting thin films is disclosed. These junctions are reliably and reproducibly formed on uniform planar substrates (10) by the action of a seed layer (40) placed intermediate the substrate (10) and the superconductor film (20). The superconductor film (22) grown atop the seed (42) is misoriented from the rest of the film (24) by an angle between 5.degree. and 90.degree.. The grain boundary (30) so formed acts as a high quality weak-link junction for superconductor devices. The performance of these junctions can be improved by the addition of buffer layers (50, 60) between the substrate (10) and the superconductor film (20).

Method of forming grain boundary junctions in high temperature

Novel superconducting oxide compositions of the formulas (YBa.sub.2 Cu.sub.3.25).sub.a O.sub.z and Y.sub.2 Ba.sub.4 Cu.sub.8 O.sub.20-x (248) are provided which can have an ordered defect structure stacked on one axis. Mi

High-temperature superconductors

To deposit a plurality of substances on a substrate while the substrate remains in a low pressure oxygen environment, several target carriers are mounted around the edge of a disc and the disc is rotated to position the targets at the focal point of a fixed laser. The target carriers are themselves rotatable in bearings on the disc and are turned by a sun gear that is carried about the same shaft that turns the disc so that the heat of the laser beam is not concentrated at one spot on the surface of the target. All the apparatus is contained in a oxygen chamber. The substrate is heated and the targets are cooled continuously.

Superconductor deposition system

Grain boundary, weak-link junctions are formed at a predermined location of a uniform, planar substrate by depositing superconducting film on two sections of the substrate. The film is grown as a bicrystal having two distinct areas of superconducting film whose crystal lattices are rotated with respect to each other, either in-plane or out-of-plane, by more than 5.degree. and less than 90.degree.. The grain boundary acts as a weak link junction. The film can be induced to grow as a bicrystal by depositing intermediate strata such as seed layers or buffer layers or by modifying the growth conditions during deposition.

Grain boundary junctions in high temperature superconductor films

A HTSC layered structure comprising a substrate such as sapphire, a strontium titanate buffer layer and a HTSC film such as YBa.sub.2 Cu.sub.3 O.sub.7 provides a superconductor having lower surface resistance and a narrower transition temperature.

High temperature superconductor-strontium titanate sapphire structures

A HTSC layered structure comprising a substrate such as calcium titanate and a HTSC film such as YBa.sub.2 Cu.sub.3 O.sub.7. Use of a thin buffer layer of calcium titanate on sapphire provides a YBa.sub.2 Cu.sub.3 O.sub.7-x film with higher critical current.

High temperature superconductor-calcium titanate structures

A substrate heater for the production of superconducting films utilizing a nickel alloy block uniformly heated with a resistance heating element fully immersed in a brazing material that fills a recess in the block. Massive electric power connectors surround the heating element leads outside the braze material so as to provide a protective heat sink therefor and also to mechanically strengthen the block against warpage.

Substrate heater utilizing protective heat sinking means

A method of forming a superconducting YBa.sub.2 Cu.sub.3 O.sub.7-x thin film with selected crystal orientation is described which comprises the steps of sputtering simultaneously Y, Ba and Cu onto the surface of a substrate, introducing oxygen at said surface during deposition, controlling the stoichiometry of the elements Y, Ba or both richer or poorer than the 1:2:3 stoichiometry within a few atom percent and followed by annealing to selectively grow an a-axis or a c-axis oriented film of YBa.sub.2 Cu.sub.3 O.sub.7-x.

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Palo Alto, CA, United States of America

Kookrin Char