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Josephson Tunneling Junction

IP.com Disclosure Number: IPCOM000093549D
Original Publication Date: 1967-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Lumpkin, O: AUTHOR

Abstract

The conventional Josephson junction consists of two superconducting films separated by an oxide layer about 30 angstroms thick. In making a Josephson junction, a metal having a relatively high transition temperature is sought. For example, lead is a preferred superconductive metal because its transition temperature of 7 degrees K is higher than most superconductive metals. In creating the oxide layer between the two superconductive films, a first layer of lead is deposited. The latter is oxidized and a second layer of lead is deposited over the oxidized layer.

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Josephson Tunneling Junction

The conventional Josephson junction consists of two superconducting films separated by an oxide layer about 30 angstroms thick. In making a Josephson junction, a metal having a relatively high transition temperature is sought. For example, lead is a preferred superconductive metal because its transition temperature of 7 degrees K is higher than most superconductive metals. In creating the oxide layer between the two superconductive films, a first layer of lead is deposited. The latter is oxidized and a second layer of lead is deposited over the oxidized layer.

However, very thin lead oxide layers are difficult to deposit reliably. The lead oxide crumbles, is not uniform in composition, or otherwise does not perform its function as a barrier layer. To overcome this shortcoming, a composite structure is made of an initial film of lead 2 onto which is deposited a nonsuperconductive layer 4, for example, of aluminum. A portion 6 of this aluminum layer is oxidized. The oxidized portion, Al(2)O(3), has stable physical characteristics and is easily formed. The Josephson tunnel junction is completed by depositing a film 8 of lead over the Al(2)O(3) layer.

The final junction is a multilayered structure composed of a superconductive layer PbAl, a barrier layer Al(2)O(3), and a second superconductive layer Pb. PbAl has the relatively high transition temperature of lead. Thus the presence of aluminum serves to obtain a good barrier layer without...