Dresden 2026 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 16: Thin Film Application
DS 16.6: Vortrag
Donnerstag, 12. März 2026, 11:00–11:15, REC/C213
Investigation of Temperature-Dependent Loss Mechanisms in Tantalum and Niobium Thin-Film Coplanar-Waveguide Resonators — •Philip Schneider1, Moritz Singer1, Harsh Gupta1, Benedikt Schoof1, and Marc Tornow1, 2 — 1TU Munich, Garching, Germany — 2Fraunhofer EMFT, Munich, Germany
Superconducting qubits can enable scalable quantum computing. Niobium (Nb) is widely used as the base superconductor, but tantalum (Ta) can improve performance by hosting fewer two-level system (TLS) losses, especially in its native oxide. We sputter-deposited Ta and Nb thin films on silicon and studied three stacks: pure Nb, Nb with a thin Ta cap, and Ta on a thin Nb seed layer, realizing distinct interface scenarios. The thin films were characterized by resistivity, critical temperature, RRR and X-ray diffraction. Coplanar waveguide resonators were fabricated from the ∼200 nm films to determine their internal quality factor (Qi) in the few GHz regime. Temperature- and power-dependent measurements (100-1700 mK, -80 to -160 dBm) were fitted with a combined TLS-quasiparticle loss model to analyze loss-channels. To probe the effect of native oxide at the metal-air interfaces, the resonators were re-measured post four weeks of air exposure. In the single-photon regime at 100 mK, the average Qi changes from 1.38×106 (BOE) to 1.19×106 (native oxide) for Nb, from 1.58×106 to 1.11×106 for Ta-capped Nb, and from 1.07×106 to 1.20×106 for Ta on an Nb seed layer. Thus, while all stacks provide Qi in the 106 range, Nb-based devices degrade post oxidation, whereas the Ta dominated film remains robust and even slightly improves.
Keywords: Superconducting qubits; Tantalum thin films; Niobium thin films; Coplanar waveguide (CPW) resonators; Internal quality factor