Characterization of Tantalum Oxide Suppression with a Noble Metal Encapsulation

Single qubit coherence remains a major limiting factor in building scalable processors based on superconducting qubits. Tantalum (Ta)-based superconducting qubits have recently been discovered to enable long lifetimes and coherence times because of their chemical robustness and well-behaved surface oxide. One of the remaining major sources of dielectric loss has been measured to be two-level systems (TLSs) residing in the amorphous native oxide layer. One strategy for avoiding such loss is to eliminate the oxide layer entirely by encapsulating tantalum with a thin noble metal film. In this presentation, I will discuss recent findings on the characterization of noble metal-encapsulated Ta films. We investigated the interface properties of gold, palladium, and gold-palladium encapsulated Ta using X-ray photoelectron spectroscopy. Our study provides insights into the mechanisms of oxidation suppression in these films, highlighting the role of noble metal encapsulation in enhancing the stability of tantalum under oxidative conditions.