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Use of Paramagnetic or other Impurities in Josephson Technology

IP.com Disclosure Number: IPCOM000084887D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Wolf, P: AUTHOR

Abstract

Paramagnetic impurities in superconductive metals drastically lower the critical temperature of conductors made of these metals. By selective introduction of such impurities, e.g., through ion implantation, it is possible to render parts of integrated circuits incorporating Josephson devices normally conductive at cryogenic temperatures.

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Use of Paramagnetic or other Impurities in Josephson Technology

Paramagnetic impurities in superconductive metals drastically lower the critical temperature of conductors made of these metals. By selective introduction of such impurities, e.g., through ion implantation, it is possible to render parts of integrated circuits incorporating Josephson devices normally conductive at cryogenic temperatures.

Mn can be introduced into Pb. Lines made of Nb can for the same purpose be either doped with paramagnetic impurities or small amounts of 0 or N. In this way, a technology which uses pure Nb as a base material only, is feasible.

The aforementioned method not only allows the making of resistors in a very simple way, but also the fabrication of tunnel junctions in which one (S-I-N) or both (N-I-N) electrodes are normal conducting, together with Josephson junctions in which both electrodes (S-I-S) are superconducting. S-I-N devices may be employed in complex circuits as diodes. N-I-N devices can be employed as linear resistors.

Since the junction oxide might survive the implantation treatment, N-I-N resistors track with properties of Josephson junctions on the same wafer. Electrical values, therefore, are a function of oxidation parameters and vary by the same amount and in the same direction as those of Josephson junctions. This property avoids the use of an extra alloy for resistors and also alleviates considerably any tolerance problems with circuits containing Joseph...