Formation and Microwave Losses of Hydrides in Superconducting Niobium Thin Films Resulting from Fluoride Chemical Processing

Abstract

Superconducting Nb thin films have recently attracted significant attention due to their utility for quantum information technologies. In the processing of Nb thin films, fluoride-based chemical etchants are commonly used to remove surface oxides that are known to affect superconducting quantum devices adversely. However, these same etchants can also introduce hydrogen to form Nb hydrides, potentially negatively impacting microwave loss performance. Here, we present comprehensive materials characterization of Nb hydrides formed in Nb thin films as a function of fluoride chemical treatments. In particular, secondary-ion mass spectrometry, X-ray scattering, and transmission electron microscopy reveal the spatial distribution and phase transformation of Nb hydrides. The rate of hydride formation is determined by the fluoride solution acidity and the etch rate of Nb2O5, which acts as a diffusion barrier for hydrogen into Nb. The resulting Nb hydrides are detrimental to Nb superconducting properties and lead to increased power-independent microwave loss in coplanar waveguide resonators. However, Nb hydrides do not correlate with two-level system loss or device aging mechanisms. Overall, this work provides insight into the formation of Nb hydrides and their role in microwave loss, thus guiding ongoing efforts to maximize coherence time in superconducting quantum devices.

References in corpus (8)

• Decoherence benchmarking of superconducting qubits
• Efficient and robust analysis of complex scattering data under noise in microwave resonators
• Investigation of microwave loss induced by oxide regrowth in high-Q Nb resonators
• Proximity breakdown of hydrides in superconducting niobium cavities
• Path toward manufacturable superconducting qubits with relaxation times exceeding 0.1 ms
• Nitrogen Plasma Passivated Niobium Resonators for Superconducting Quantum Circuits
• Effects of anisotropy and disorder on the superconducting properties of Niobium
• Fabrication and surface treatment of electron-beam evaporated niobium for low-loss coplanar waveguide resonators

Cited by in corpus (4)

• Reversing Hydrogen-Related Loss in $\alpha$-Ta Thin Films for Quantum Device Fabrication
• Enhanced Superconducting Qubit Performance Through Ammonium Fluoride Etch
• Low-loss Nb on Si superconducting resonators from a dual-use spintronics deposition chamber and with acid-free post-processing
• Fabrication effects on Niobium oxidation and surface contamination in Niobium-metal bilayers using X-ray photoelectron spectroscopy