Nitrogen plasma passivated niobium resonators for superconducting quantum circuits

  title={Nitrogen plasma passivated niobium resonators for superconducting quantum circuits},
  author={Kai Zheng and D. Kowsari and N. J. Thobaben and X. Du and X Song and Sheng Ran and Erik A. Henriksen and D. S. Wisbey and Kater W. Murch},
  journal={Applied Physics Letters},
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… 
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