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Browse Prior Art Database

Low Resistance Ohmic Contacts to Oxide Superconductors

IP.com Disclosure Number: IPCOM000108175D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 1 page(s) / 25K

Publishing Venue

IBM

Related People

Jackson, TN: AUTHOR [+3]

Abstract

Ohmic contacts to superconductors are important because contact resistance is responsible for parasitic voltages and undesirable heating in devices and circuits and can limit the current- carrying capacity of superconducting wiring. Disclosed is a technique which has been demonstrated to yield stable, reliable contacts to single-crystal oxide superconductors and which is applicable to ceramic materials and films, even if the material is coated with an insulating layer.

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Low Resistance Ohmic Contacts to Oxide Superconductors

      Ohmic contacts to superconductors are important because contact
resistance is responsible for parasitic voltages and undesirable
heating in devices and circuits and can limit the current- carrying
capacity of superconducting wiring.  Disclosed is a technique which
has been demonstrated to yield stable, reliable contacts to
single-crystal oxide superconductors and which is applicable to
ceramic materials and films, even if the material is coated with an
insulating layer.

      The technique consists of (1) Sputter etching of the sample
surface, (2) evaporation of a metallic contact material, and (3)
annealing to allow interdiffusion of this metal and the sample.  Step
(1) is optional and can remove some of the non-conducting surface
layer.  It cannot provide a superconducting surface due to
preferential sputtering effects, so it is desirable to stop etching
before reaching the superconductor.  The metal in step (2) should be
a low melting point alloy, such as one based on In (e.g., In-Au). In
step (3), interdiffusion takes place at temperatures low enough
and/or times short enough to avoid degradation of device structures.
This technique has been used to fabricate contacts having resistances
of a few tenths of a micro-ohm times square centimeter at 4.2 K to
single-crystal YBCO.

      Disclosed anonymously.