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Fabrication of Planar Josephson Junctions by Laser Irradiation

IP.com Disclosure Number: IPCOM000085574D
Original Publication Date: 1976-Apr-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Braslau, N: AUTHOR [+4]

Abstract

Planar Josephson junctions have been successfully fabricated [1] by ion implantation, making use of the observation that implantation into certain superconducting metal films raises the critical temperature, T(c). If a micron wide strip of film is masked by photo or electron-beam resist, its T(c) is not altered by the implantation. Operating this device at an intermediate temperature produces a SNS Josephson junction which displays all the expected properties.

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Fabrication of Planar Josephson Junctions by Laser Irradiation

Planar Josephson junctions have been successfully fabricated [1] by ion implantation, making use of the observation that implantation into certain superconducting metal films raises the critical temperature, T(c). If a micron wide strip of film is masked by photo or electron-beam resist, its T(c) is not altered by the implantation. Operating this device at an intermediate temperature produces a SNS Josephson junction which displays all the expected properties.

Thus, a superconducting film with a micron wide region with lower (or zero) T(c) is required. A method is described for making such a structure without the need of photoresist steps or extensive exposure to the entire film structure.

It is known that certain amorphous films show a higher T(c) than the bulk or crystalline state. A suitably prepared film is exposed to a high-energy pulsed and focussed laser beam, which is scanned normal to the current direction at a power level and rate so as to melt and recrystallize the exposed region. The operation need take place only where a Josephson junction is to be formed. A favorable material for an embodiment is Mo. Films have been grown with T(c) Approx. 5 degrees K. Bulk crystalline Mo has a much lower critical temperature (T(c) Approx. 0.9 degrees K), so if remelting occurs, one would have a SNS junction for T < T8c) film.

The width of such a normal region depends on the focal diameter of the laser u...