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All-Nitride Superconducting Tunnel Junctions

IP.com Disclosure Number: IPCOM000044277D
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Gallagher, WJ: AUTHOR [+2]

Abstract

Three layers of niobium nitride/silicon nitride/niobium nitride form a superconducting tunnel junction with good control of electrode properties and minimal transition width. When a superconducting tunnel junction is fabricated, an oxidation with oxygen or air is always included as part of the tunnel barrier processing. The oxidations are used to form the tunnel barrier by oxidation of the base electrode. They are also necessary to oxidize underlying electrode metallurgy through pinholes in discontinuous barrier films, such as deposited semiconductors. The introduction of oxygen into the vacuum system introduces several process problems. A three-layer, all-refractory superconducting tunnel junction, composed only of nitride layers, avoids oxide process problems.

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All-Nitride Superconducting Tunnel Junctions

Three layers of niobium nitride/silicon nitride/niobium nitride form a superconducting tunnel junction with good control of electrode properties and minimal transition width. When a superconducting tunnel junction is fabricated, an oxidation with oxygen or air is always included as part of the tunnel barrier processing. The oxidations are used to form the tunnel barrier by oxidation of the base electrode. They are also necessary to oxidize underlying electrode metallurgy through pinholes in discontinuous barrier films, such as deposited semiconductors. The introduction of oxygen into the vacuum system introduces several process problems. A three-layer, all-refractory superconducting tunnel junction, composed only of nitride layers, avoids oxide process problems. The structure of niobium nitride/silicon nitride/niobium nitride is such a tunnel junction. Refractory electrodes, such as niobium or niobium nitride, provide mechanical stability to the sensitive junction structures. The nitridation of niobium decreases the sensitivity of this electrode to system impurities. Formation of niobium nitride/silicon nitride interfaces leads to relatively sharp, well-defined interfaces. By using two sputtering targets, niobium and silicon, it is possible to deposit the nitride films sequentially by reactive sputtering, without exposing the sample or system to oxygen until the junction structure is completed. The sandwich structure c...