Current browse context:
physics.app-ph
Change to browse by:
References & Citations
Physics > Applied Physics
Title: Oxygen Vacancies in Niobium Pentoxide as a Source of Two-Level System Losses in Superconducting Niobium
(Submitted on 30 Aug 2021 (v1), last revised 24 Apr 2024 (this version, v3))
Abstract: We identify a major source of quantum decoherence in three-dimensional superconducting radio-frequency (SRF) resonators and two-dimensional transmon qubits composed of oxidized niobium: oxygen vacancies in the niobium pentoxide which drive two-level system (TLS) losses. By probing the effect of sequential \textit{in situ} vacuum baking treatments on the RF performance of bulk Nb SRF resonators and on the oxide structure of a representative Nb sample using time-of-flight secondary ion mass spectrometry (ToF-SIMS), we find a non-monotonic evolution of cavity quality factor $Q_0$ which correlates with the interplay of Nb\textsubscript{2}O\textsubscript{5} vacancy generation and oxide thickness reduction. We localize this effect to the oxide itself and present the insignificant role of diffused interstitial oxygen in the underlying Nb by regrowing a new oxide \textit{via} wet oxidation which reveals a mitigation of aggravated TLS losses. We hypothesize that such vacancies in the pentoxide serve as magnetic impurities and are a source of TLS-driven RF loss.
Submission history
From: Daniel Bafia [view email][v1] Mon, 30 Aug 2021 16:24:07 GMT (461kb,D)
[v2] Thu, 25 Aug 2022 21:33:23 GMT (479kb,D)
[v3] Wed, 24 Apr 2024 21:03:06 GMT (621kb,D)
Link back to: arXiv, form interface, contact.