Nb and Nb-based A15 compound tunnel junctions fabricated using a new CF/sub 4/ cleaning process
A new surface cleaning technique, the CF/sub 4/ Cleaning Process (CFCP), is proposed for the fabrication of Nb and Nb-based A15 compound tunnel junctions with native oxide barriers. The effects of fabrication conditions and these superconducting material properties on the characteristics of these junctions with Pb or Pb alloy counterelectrodes are investigated. High-quality junctions with a well-defined gap, no knee and very low excess conductance are successfully fabricated through the conventional lift-off technique for A15 compounds (Nb/sub 3/A1, Nb/sub 3/Ge and Nb/sub 3/Si) as well as Nb. Arrays of 100 series-connected 2 ..mu..m/phi/ Nb/PbBi junctions are fabricated with the standard deviation (sigma) of critical current (J /SUB c/ = 15.1 KA/cm/sup 2/) equal to 2.5%. The CFCP mechanism that contributes to the formation of such good junctions is studied using in-situ X-ray photoelectron spectroscopy (XPS). Chemical shifts of the Nb 3d levels on the CF/sub 4/ plasma-cleaned Nb surfaces indicate the presence of an Nb-F layer. These XPS spectra show that the tunnel barrier is composed of mixed Nb/sub 2/O/sub 5/ and Nb-F-O compounds.
- Research Organization:
- Ibaraki Electrical Communication Laboratory, NTT, Tokai, Ibaraki
- OSTI ID:
- 6484952
- Report Number(s):
- CONF-840937-
- Journal Information:
- IEEE Trans. Magn.; (United States), Journal Name: IEEE Trans. Magn.; (United States) Vol. MAG 21:2; ISSN IEMGA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104 -- Metals & Alloys-- Physical Properties
420201* -- Engineering-- Cryogenic Equipment & Devices
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALLOYS
ALUMINIUM ALLOYS
CARBON COMPOUNDS
CARBON FLUORIDES
CLEANING
CRITICAL CURRENT
CURRENTS
DIFFUSION BARRIERS
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
FABRICATION
FLUORIDES
FLUORINE COMPOUNDS
GERMANIUM ALLOYS
HALIDES
HALOGEN COMPOUNDS
JUNCTIONS
LEAD ALLOYS
NIOBIUM ALLOYS
PHYSICAL PROPERTIES
SILICON ALLOYS
SPECTROSCOPY
SUPERCONDUCTING JUNCTIONS
SUPERCONDUCTIVITY
SURFACE CLEANING
SURFACE FINISHING
TUNNEL EFFECT
X-RAY SPECTROSCOPY