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Conductive Oxide Contacts for High Tc Superconductors

IP.com Disclosure Number: IPCOM000112734D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+5]

Abstract

One of the problems in making ohmic contact to the high Tc superconductors is that most metals will react with some of the oxygen in the superconductor under the contact. This reaction can leave an oxygen-deficient interface, causing a lowering of the transition temperature, or a nonsuperconducting layer. In addition, the metal oxide, if it is an insulator, will form a barrier. Also, the conditions used for depositing the metal - vacuum or inert gas plasma - may cause oxygen loss from the surface of the superconductor. Disclosed is a method that eliminates these problems by using conductive metal oxides as contacts for the oxide superconductors.

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Conductive Oxide Contacts for High Tc Superconductors

      One of the problems in making ohmic contact to the high Tc
superconductors is that most metals will react with some of the
oxygen in the superconductor under the contact.  This reaction can
leave an oxygen-deficient interface, causing a lowering of the
transition temperature, or a nonsuperconducting layer.  In addition,
the metal oxide, if it is an insulator, will form a barrier.  Also,
the conditions used for depositing the metal - vacuum or inert gas
plasma - may cause oxygen loss from the surface of the
superconductor.  Disclosed is a method that eliminates these problems
by using conductive metal oxides as contacts for the oxide
superconductors.

      There are a number of oxides that are intrinsic metallic
conductors as opposed to doped semiconductors like Indium Tin Oxide.
Many of these conductive oxides have the rutile structure, i.e., the
structure of the dioxides of Ti, Cr, Os, Ru, Ir, Sn and Ta.  The
dioxides of V, Nb, Mo and W have slightly distorted variations of
this structure.  Not all of these compounds are metallic conductors:
'TiO' sub <2>, 'VO' sub 2, and 'PtO' sub 2 are semiconductors.
Furthermore, many of the conductive oxides react with excess oxygen
to form a higher oxide which is insulating (e.g., 'MoO' sub 2 and
'WO' sub 2).  They act much like a reactive metal as a contact
because they take oxygen away from the superconductor and leave an
insulating higher oxide ('MoO' sub 3 or 'WO' sub 3) at the interface.
That leaves the dioxides of the platinum group and related metals,
Ru, Rh, Os and Ir.  In the case of 'RuO' sub 2, the conductive rutile
phase is the highest stable oxide....