Work

Broadband RF Characterization and Modeling of Superconducting Coplanar Waveguides

Year: 2024

Type: article

Abstract: We present the RF characterization of 2-µm-wide superconducting coplanar waveguides made of 100-nm-thick niobium (Nb) or niobium nitride (NbN) films fabricated on 200 mm silicon wafers. Measurements of the two-ports S-parameters up to 25 GHz in a 4.7K–14 K temperature range with an added direct current up to 115 mA were done using a cryogenic probe station. With proper RF calibration and de-embedding procedure, both temperature and dc current dependence of the RF superconducting properties are analyzed. We report a kinetic inductance of 0.15 pH/$\square$, a critical current density of 50 MA/cm$^{2}$, and a critical temperature of 8.9 K for Nb as well as 4.27 pH/$\square$, 3 MA/cm$^{2}$, and 13.8 K for NbN. A telegraphist transmission line model taking into account the BCS theory has been developed and the comparison with the measurements is discussed.

Source: IEEE Transactions on Applied Superconductivity

DOI: 10.1109/tasc.2024.3516210