1. Nitrogen Plasma Passivated Niobium Resonators for Superconducting Quantum Circuits
- Author
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Zheng, K., Kowsari, D., Thobaben, N. J., Du, X., Song, X., Ran, S., Henriksen, E. A., Wisbey, D. S., and Murch, K. W.
- Subjects
Physics - Applied Physics ,Condensed Matter - Superconductivity ,Quantum Physics - Abstract
Microwave loss in niobium metallic structures used for superconducting quantum circuits is limited by a native surface oxide layer formed over a timescale of minutes when exposed to an ambient environment. In this work, we show that nitrogen plasma treatment forms a niobium nitride layer at the metal-air interface which prevents such oxidation. X-ray photoelectron spectroscopy confirms the doping of nitrogen more than 5 nm into the surface and a suppressed oxygen presence. This passivation remains stable after aging for 15 days in an ambient environment. Cryogenic microwave characterization shows an average filling factor adjusted two-level-system loss tangent $\rm{F\delta_{TLS}}$ of $(2.9\pm0.5)\cdot10^{-7}$ for resonators with 3 $\rm{\mu}$m center strip and $(1.0\pm0.3)\cdot10^{-7}$ for 20 $\rm{\mu}$m center strip, exceeding the performance of unpassivated samples by a factor of four., Comment: 7 pages, 5 figures
- Published
- 2022
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