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arXiv · 2108.05354

Fabrication and surface treatment of electron-beam evaporated niobium for low-loss coplanar waveguide resonators

D. Kowsari·K. Zheng·J. T. Monroe·N. J. Thobaben·X. Du·P. M. Harrington·E. A. Henriksen·D. S. Wisbey·K. W. Murch
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Abstract

We characterize low-loss electron-beam evaporated niobium thin films deposited under ultra-high vacuum conditions. Slow deposition yields films with a high superconducting transition temperature ($9.20 \pm 0.06 \rm ~K$) as well as a residual resistivity ratio of $4.8$. We fabricate the films into coplanar waveguide resonators to extract the intrinsic loss due to the presence of two-level-system fluctuators using microwave measurements. For a coplanar waveguide resonator gap of $2~μ\rm m$, the films exhibit filling-factor-adjusted two-level-system loss tangents as low as $1.5 \times 10^{-7}$ with single-photon regime internal quality factors in excess of one million after removing native surface oxides of the niobium.

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D. Kowsari, K. Zheng, J. T. Monroe, N. J. Thobaben, X. Du, P. M. Harrington, E. A. Henriksen, D. S. Wisbey, K. W. Murch. 2021-10-04. Fabrication and surface treatment of electron-beam evaporated niobium for low-loss coplanar waveguide resonators. https://doi.org/10.1063/5.0066441

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