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

α-Tantalum (α-Ta) is becoming an increasingly popular material for superconducting qubit fabrication due to the low microwave loss of its stable native oxide [1,2]. However, hydrogen absorption during fabrication processes, such as oxide cleaning with fluorine-based etchants, could degrade Ta film performance by increasing microwave loss. In this work, we demonstrate that hydrogen can enter α-Ta thin films when the native oxide, an excellent hydrogen diffusion barrier, is removed, leading to the formation of tantalum hydrides (TaH_x). These hydrides contribute to power-independent ohmic loss in high-quality resonators, similar to what was recently discovered for Nb [3]. We further show that annealing at 500°C in ultra-high vacuum effectively removes the hydrogen and restores the resonators’ quality factors. Our findings highlight a pathway for improving the performance of Ta-based quantum devices by mitigating hydrogen-induced losses, thus enabling more aggressive and faster surface cleaning techniques during fabrication.



[1] Place, A. P. M. et al. Nature Communications 12, 1779 (2021).

[2] Wang, C. et al. npj Quantum Inf 8, 1 (2022).

[3] Torres-Castanedo, C. G. et al. Advanced Functional Materials 34, 2401365 (2024).