Elucidating the local atomic and electronic structure of amorphous oxidized superconducting niobium films

Abstract

Qubits made from superconducting materials are a mature platform for quantum information science application such as quantum computing. However, materials-based losses are now a limiting factor in reaching the coherence times needed for applications. In particular, knowledge of the atomistic structure and properties of the circuit materials is needed to identify, understand, and mitigate materials-based decoherence channels. In this work we characterize the atomic structure of the native oxide film formed on Nb resonators by comparing fluctuation electron microscopy experiments to density functional theory calculations, finding that an amorphous layer consistent with an Nb${}_2$O${}_5$ stoichiometry. Comparing X-ray absorption measurements at the Oxygen K edge with first-principles calculations, we find evidence of d-type magnetic impurities in our sample, known to cause impedance in proximal superconductors. This work identifies the structural and chemical composition of the oxide layer grown on Nb superconductors, and shows that soft X-ray absorption can fingerprint magnetic impurities in these superconducting systems.

arXiv comment7 pages, 4 figures. The following article has been submitted to Applied Physics Letters

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Cited by in corpus (6)

• Oxygen Vacancies in Niobium Pentoxide as a Source of Two-Level System Losses in Superconducting Niobium
• Argon milling induced decoherence mechanisms in superconducting quantum circuits
• Structural spillage: an efficient method to identify non-crystalline topological materials
• Unravelling the atomic and electronic structure of nanocrystals on superconducting Nb(110): Impact of the oxygen monolayer
• Quasiparticle spectroscopy in technologically-relevant niobium using London penetration depth measurements
• Multi-modal electron microscopy study on decoherence sources and their stability in Nb based superconducting qubit