Reducing TLS loss in tantalum resonators using titanium sacrificial layers

We demonstrate a substantial reduction in two-level system (TLS) loss in tantalum (Ta) coplanar waveguide (CPW) resonators fabricated on high-resistivity silicon (Si) substrates through the use of an ultrathin titanium (Ti) sacrificial layer. A 2 Å Ti film, deposited atop pre-sputtered alpha-Ta, acts as a solid-state oxygen getter that chemically modifies the native Ta oxide at the metal–air (MA) interface. After device fabrication, the Ti is removed using buffered oxide etchant (BOE), leaving behind a chemically reduced Ta oxide surface. Subsequent high-vacuum annealing further suppresses TLS loss. Resonators treated with this process exhibit internal quality factors exceeding an average of two million in the single-photon regime across ten devices—over four times higher than otherwise identical devices lacking the Ti layer. These results highlight the critical role of interfacial oxide chemistry in superconducting loss and reinforce atomic-scale surface engineering as an effective approach to improving coherence in Ta-based quantum circuits. The method is fully compatible with existing fabrication workflows applicable to Ta films, and is substrate-agnostic—offering a practical route to further extending lifetimes in Ta-based superconducting qubits.