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Counter Electrode Material For Josephson Junction Device

IP.com Disclosure Number: IPCOM000048879D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Huang, HW: AUTHOR [+3]

Abstract

Pb-alloy Josephson junction device failures which have been observed during repeated thermal cycling between 300K and 4.2K are believed to be caused by microstructure changes in the electrode films. Changes large enough to rupture the ultra-thin tunnel barrier oxide were observed in a repeatedly cycled film when strain induced by thermal expansion coefficient mismatch between the film and the substrate was relaxed upon cycling between 300K and 4.2K.

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Counter Electrode Material For Josephson Junction Device

Pb-alloy Josephson junction device failures which have been observed during repeated thermal cycling between 300K and 4.2K are believed to be caused by microstructure changes in the electrode films. Changes large enough to rupture the ultra-thin tunnel barrier oxide were observed in a repeatedly cycled film when strain induced by thermal expansion coefficient mismatch between the film and the substrate was relaxed upon cycling between 300K and 4.2K.

A technique is described to prepare the counter electrode material of a Josephson junction device with improved thermal stability. For Pb-In-Au base electrode films, the strain relaxation and microstructure changes were reduced by reducing the average grain size of the film, and a significant improvement was obtained in the film stability during repeated thermal cycling. For the epsilon- phase Pb-Bi alloy films of interest for junction counter electrodes, the microstructure changes are also expected to be reduced by reducing the strain relaxation during thermal cycling.

Pb-Bi films with a Bi concentration of about 26 percent to 29 percent are deposited at a thickness of 400 nanometers at low substrate temperature of about 77K to 273K using a single source coevaporation. A thin layer less than 10 nanometers of Au element is then deposited on the surface of the Pb-Bi film, which diffuses into the grain boundaries and prevents grain growth and/or strengthens grain...