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HIGH Tc SUPERCONDUCTING OXIDE SANDWICH STRUCTURES AND TUNNEL JUNCTIONS

IP.com Disclosure Number: IPCOM000034373D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gambino, RJ: AUTHOR [+6]

Abstract

Thin superconducting oxide films of the YBaCuO composition ( 1- 2-3 ) have been made which are superconducting to temperatures of about 90oK. These films are difficult to utilize in a layered or sandwich structure due to the roughness of the ceramic film (roughnesses on the order of 0.5 mm can often be seen in nominally 1 micrometer thick films). A second difficulty in making superconductor-insulator-superconductor (SIS) sandwich structures is in making a thin insulator that can survive the 900oC firing required to make good superconductors. A novel solution to these important problems is herein disclosed. A thin insulating film sandwiched between two high Tc superconductors, as described below, can solve this problem. The YBaCuO composition will be used as an example but any ceramic superconducting film can also be used.

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HIGH Tc SUPERCONDUCTING OXIDE SANDWICH STRUCTURES AND TUNNEL JUNCTIONS

Thin superconducting oxide films of the YBaCuO composition ( 1- 2-3 ) have been made which are superconducting to temperatures of about 90oK. These films are difficult to utilize in a layered or sandwich structure due to the roughness of the ceramic film (roughnesses on the order of 0.5 mm can often be seen in nominally 1 micrometer thick films). A second difficulty in making superconductor-insulator-superconductor (SIS) sandwich structures is in making a thin insulator that can survive the 900oC firing required to make good superconductors. A novel solution to these important problems is herein disclosed. A thin insulating film sandwiched between two high Tc superconductors, as described below, can solve this problem. The YBaCuO composition will be used as an example but any ceramic superconducting film can also be used. In the as-deposited state, the YBaCuO films are not superconducting but are smooth, fine-grained, amorphous-like films. Upon annealing, they become very rough. Most thin insulators will not survive such roughness. MgO has been sputtered on the as-deposited film after which YBaCuO is deposited as the top or counter electrode before annealing. Thus, all the surfaces are smooth and the thin insulator is intact. When the entire structure is then annealed, the free or top surface becomes rough while the interfaces surrounding the thin insulator are confined and remain much smoothe...