Thermal stability of Nb/a-Nb{sub x}Si{sub 1-x}/Nb Josephson junctions

Journal Article · Thu Feb 01 00:00:00 EST 2007 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.75.054514· OSTI ID:20976677

Baek, B; Dresselhaus, P D; Benz, S P ^[1]

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1. National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

As a high-resistivity normal-metal barrier for superconducting Josephson junctions, metal-silicon alloys appear to be a good replacement for noble metals and have been applied to the development of quantum voltage standard circuits. We observed that the electrical properties of Nb-based junctions made with amorphous Nb{sub x}Si{sub 1-x} barriers were slowly evolving over time when stored at room temperature. After systematically investigating both junctions and thin films, we have concluded that the changes in junction electrical parameters are due to changes in the amorphous Nb{sub x}Si{sub 1-x} and not due to barrier-electrode interface effects. The resistivity of amorphous Nb{sub x}Si{sub 1-x} increases after heat treatment at temperatures as low as 80 deg. C when the Nb concentration is less than 33%, that of NbSi{sub 2}. Furthermore, we found that annealed barriers behave similarly to barriers with the Nb concentration intentionally reduced to obtain smaller critical current and larger normal resistance with the same barrier thickness, as explained by our I{sub c}-R{sub n} relation developed based on the dirty-limit superconductor-normal-metal-superconductor Josephson junction theory. To explain these effects, we adopt and corroborate a microscopic picture based on alloy phase stability that was previously demonstrated by others. We also successfully demonstrate a method to stabilize junctions made with Nb{sub x}Si{sub 1-x} barriers by intentionally annealing wafers during fabrication.

• OSTI ID: 20976677
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 75, Issue 5; Other Information: DOI: 10.1103/PhysRevB.75.054514; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMORPHOUS STATE
ANNEALING
CRITICAL CURRENT
ELECTRIC CONDUCTIVITY
JOSEPHSON EFFECT
JOSEPHSON JUNCTIONS
NIOBIUM
NIOBIUM ALLOYS
PHASE STABILITY
SILICON ALLOYS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
THICKNESS
THIN FILMS
TYPE-I SUPERCONDUCTORS