Stress dependent oxidation of sputtered niobium and effects on superconductivity

Journal Article · Fri Feb 28 04:00:00 EST 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4866554· OSTI ID:22278015

Wolfley, Steve; Monson, Todd; Clark, Blythe G.; Shaner, Eric; Jarecki, Robert ^[1]

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1. Sandia National Labs, MESA Fabrication Facility PO Box 5800 MS 1084, Albuquerque, New Mexico 87185-1084 (United States)

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.

• OSTI ID: 22278015
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 115; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

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