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Josephson Superconductive Devices

IP.com Disclosure Number: IPCOM000082906D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Tsuei, CC: AUTHOR

Abstract

The conventional configurations of Josephson superconductive devices are usually in the form of 1) crossed thin-metal films separated by a thin-insulating oxide layers, 2) a narrow (weakly superconducting) link between two layer areas of superconductive film (Dayem bridge)*, or 3) a combination of 1) and 2) and making use of the proximity effect (Notarys bridge).**

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Josephson Superconductive Devices

The conventional configurations of Josephson superconductive devices are usually in the form of 1) crossed thin-metal films separated by a thin-insulating oxide layers, 2) a narrow (weakly superconducting) link between two layer areas of superconductive film (Dayem bridge)*, or 3) a combination of 1) and 2) and making use of the proximity effect (Notarys bridge).**

Because these configurations either rely on layers of different materials that are put on top of each other or on the narrowness of the weak link, these devices cannot stand many repeated cyclings between room temperature and liquid helium temperature. In the case of configurations 2) and 3), significant (and undesirable) self-heating effects have been observed.

The following technique of fabricating a Josephson superconductive device is an improvement over the existing designs. Stripes of superconducting materials, S, are formed on an insulating substrate as shown in the figure. This step can be performed with any thin film deposited technique such as vapor-deposition or sputtering. Then, a thin strip M of magnetic material 0.1 to 3 Mu m wide, such as Fe, Ni, Co, Gd, etc. (in some instances, nonmagnetic material can also be used) is deposited perpendicular to stripes S. The composite structure is then annealed at a temperature sufficient to permit the atoms of M to diffuse into S. The diffused region of S has a lower T(c) (superconducting transition temperature) and s...