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Title: Stress dependent oxidation of sputtered niobium and effects on superconductivity

We report on the suppression of room temperature oxidation of DC sputtered niobium films and the effects upon the superconductive transition temperature, T{sub c}. Niobium was sputter-deposited on silicon dioxide coated 150 mm wafers and permitted to oxidize at room temperature and pressure for up to two years. Resistivity and stress measurements indicate that tensile films greater than 400 MPa resist bulk oxidation with measurements using transmission electron microscope, electron dispersive X-ray spectroscopy, x-ray photoelectric spectroscopy, and secondary ion mass spectrometry confirming this result. Although a surface oxide, Nb{sub 2}O{sub 5}, consumed the top 6–10 nm, we measure less than 1 at. % oxygen and nitrogen in the bulk of the films after the oxidation period. T{sub c} measurements using a SQUID magnetometer indicate that the tensile films maintained a T{sub c} approaching the dirty superconductive limit of 8.4 K after two years of oxidation while maintaining room temperature sheet resistance. This work demonstrates that control over niobium film stress during deposition can prevent bulk oxidation by limiting the vertical grain boundaries ability to oxidize, prolonging the superconductive properties of sputtered niobium when exposed to atmosphere.
Authors:
; ; ; ; ;  [1]
  1. Sandia National Labs, MESA Fabrication Facility PO Box 5800 MS 1084, Albuquerque, New Mexico 87185-1084 (United States)
Publication Date:
OSTI Identifier:
22278015
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 8; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; GRAIN BOUNDARIES; MASS SPECTROSCOPY; NIOBATES; NIOBIUM; NIOBIUM OXIDES; NITROGEN; OXIDATION; SILICON OXIDES; SPUTTERING; SQUID DEVICES; STRESSES; SUPERCONDUCTIVITY; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; TRANSITION TEMPERATURE; TRANSMISSION ELECTRON MICROSCOPY; X-RAY SPECTROSCOPY