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High Temperature Superconductor Josephson Tunnel Junctions with Beryllium Oxide Tunnel Barriers

IP.com Disclosure Number: IPCOM000114364D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Raider, SI: AUTHOR

Abstract

The formation of Josephson tunnel barrier junctions with short coherence length, high temperature superconducting electrodes requires minimizing 1) structural disorder at superconductor surfaces adjacent to an insulating tunnel barrier and 2) interdiffusions and chemical reactions between the superconductors and the insulating tunnel barrier. A high temperature superconducting Josephson tunnel junction structure is proposed with a beryllium oxide, BeO, tunnel barrier to meet these requirements. The excellent material properties of BeO make this structure unique (1).

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High Temperature Superconductor Josephson Tunnel Junctions with Beryllium
Oxide Tunnel Barriers

      The formation of Josephson tunnel barrier junctions with short
coherence length, high temperature superconducting electrodes
requires minimizing 1) structural disorder at superconductor surfaces
adjacent to an insulating tunnel barrier and 2) interdiffusions and
chemical reactions between the superconductors and the insulating
tunnel barrier.  A high temperature superconducting Josephson tunnel
junction structure is proposed with a beryllium oxide, BeO, tunnel
barrier to meet these requirements.  The excellent material
properties of BeO make this structure unique (1).

      BeO, is a chemically stable, atomically dense, covalently
bonded, homogeneous, highly refractory (m.p. 2570 degrees C)
material.
BeO deposited at high temperature (> 800 degrees C) is so exceedingly
inert that it dissolves only in a hot syrup of concentrated sulfuric
acid and ammonium sulfate (2).  Films of BeO have been deposited by
several techniques, which include reactive rf sputtering (3), laser
evaporation (4), and the reactive ionized beam cluster technique (5).
Films of BeO deposited by the reactive ionized beam cluster technique
have been deposited epitaxially on sapphire (5).  This material is an
excellent insulator with a resistivity of 10 sup(16) ohm-cm at 300ºC
and has an index of refraction of 1.7.  A report (6)  has described
the successful use of BeO as a substrate for the high temperature
supe...