Browse Prior Art Database

High Quality Josephson Tunnel Junctions for Device Operation at Temperatures > 10 degree K

IP.com Disclosure Number: IPCOM000112612D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Raider, S: AUTHOR

Abstract

Recently, a relatively high quality Josephson tunnel junction composed of single crystal NbN/MgO/NbN was reported (1) that can operate at temperatures > 10 degree K. Operation at temperatures > 10 degree K simplifies device operation and greatly reduces refrigeration costs. However, fabrication of these junction structures is difficult because it depends on epitaxial growth of the three layers on a crystalline MgO substrate and on a uniform deposition of MgO barrier layers < 1 nm thick.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 54% of the total text.

High Quality Josephson Tunnel Junctions for Device Operation at Temperatures
>  10 degree K

      Recently, a relatively high quality Josephson tunnel junction
composed of single crystal NbN/MgO/NbN was reported (1) that can
operate at temperatures >  10 degree K.  Operation at temperatures >
10 degree K simplifies device operation and greatly reduces
refrigeration costs.  However, fabrication of these junction
structures is difficult because it depends on epitaxial growth of the
three layers on a crystalline MgO substrate and on a uniform
deposition of MgO barrier layers <  1 nm thick.

   A new multilayer superconducting Josephson junction structure,
NbN/Nb/Al/Al&sub2.O&sub3./Nb/NbN, is proposed which can also operate
at temperatures >  10 degree K.  Device operation at a temperature >
10ºK depends on the proximity effect.  However, the individual
steps of the junction processing are well established and currently
produce the highest quality Josephson junction devices.  Furthermore,
there is no substrate constraint; the base electrode can be deposited
on amorphous SiO&sub2..

   The base electrode structure is formed by reactively sputtering
NbN films.  NbN films are reproducibly deposited with a T sub c of
~ 16 degree K.  High quality, tunnel junctions are made with
Nb/Al structures using conventional process but with reduced Nb and
Al film thicknesses.  Without breaking vacuum after NbN deposition, a
thin (< 5 nm) Nb film is deposited onto the NbN sur...