Developing a Chemical and Structural Understanding of the Surface Oxide in a Niobium Superconducting Qubit

Understand

Superconducting thin films of niobium have been extensively employed in transmon qubit architectures.

• Although these architectures have demonstrated remarkable improvements in recent years, further improvements in performance through materials engineering will aid in large-scale deployment.
• Here, we use information retrieved from secondary ion mass spectrometry and electron microscopy to conduct a detailed assessment of the surface oxide that forms in ambient conditions for transmon test qubit devices patterned from a niobium film.
• We observe that this oxide exhibits a varying stoichiometry with NbO and NbO$_2$ found closer to the niobium film and Nb$_2$O$_5$ found closer to the surface.