Thermal Stability of Nb/a-NbxSi1-x/Nb Josephson Junctions
Burm Baek, Paul Dresselhaus, Samuel Benz
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 NbxSi1-x barriers were evolving slightly over time when stored at room temperature. After systematically investigating both junctions and thin films, we have concluded that the changes are due to an annealing of the amorphous NbxSi1-x. The resistivity of amorphous NbxSi1-x. increases after a heat treatment at as low as 80 'aC when the Nb concentration is less than 33%, that of NbSi2. Furthermore, these 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 Ic-Rn relation developed based on the dirty-limit superconductor-normal metal-superconductor Josephson junction theory. To explain these effects, we present a microscopic picture based on alloy phase stability. We also successfully demonstrated a method to stabilize junctions made with NbxSi1-x barriers by intentionally annealing wafers during fabrication.
Physical Review B (Condensed Matter and Materials Physics)
, Dresselhaus, P.
and Benz, S.
Thermal Stability of Nb/a-NbxSi1-x/Nb Josephson Junctions, Physical Review B (Condensed Matter and Materials Physics), [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=32429
(Accessed February 28, 2024)