Reversing Hydrogen-Related Loss in α-Ta Thin Films for Quantum Device Fabrication

Abstract

α-Tantalum (α-Ta) is an emerging material for superconducting qubit fabrication due to the low microwave loss of its stable native oxide. However, hydrogen absorption during fabrication, particularly when removing the native oxide, can degrade performance by increasing microwave loss. This work demonstrates that hydrogen can enter α-Ta thin films when exposed to 10 vol% hydrofluoric acid for 3 min or longer, leading to an increase in power-independent ohmic loss in high-Q resonators at millikelvin temperatures. It is further shown that annealing at 500 °C in ultra-high vacuum (10−8 Torr) for 1 h fully removes hydrogen and restores the resonators’ intrinsic quality factors to ≈4 million at the single-photon level. These findings identify a previously unreported loss mechanism in α-Ta and offer a pathway to reverse hydrogen-induced degradation in quantum devices based on α-Ta and, by extension also Nb, enabling more robust fabrication processes for superconducting qubits.