Work

Effects of the thin-film thickness on superconducting NbTi microwave resonators for on-chip cryogenic thermometry

Year: 2025

Type: article

Abstract: Superconducting microwave resonators have recently gained a primary importance in the development of cryogenic applications, such as circuit quantum electrodynamics, electron spin resonance spectroscopy and particles detection for high-energy physics and astrophysics. In this work, we investigate the influence of the film thickness on the temperature response of microfabricated Nb 50 Ti 50 superconducting resonators. S-shaped split ring resonators (S-SRRs), approximately 20 nm to 150 nm thick, are designed to be electromagnetically coupled with standard Cu coplanar waveguides (CPWs) and their microwave properties are characterised at temperatures below 10 K . The combined contributions of the kinetic inductance L K ( T ) increase and the decreasing loaded quality factor Q L , for thinner films, induce an optimum condition on the temperature sensitivity and resolution of the resonators. A noise equivalent temperature as low as ( 0.53 ± 0.09 ) μ K Hz − 1 / 2 , at 1 Hz , is reported for 100 nm thick resonators at 4.2 K . We also asses the possibility of implementing a multiplexed frequency readout, allowing for the simultaneous temperature tracking of several sensors along a single CPW. Such results demonstrate the possibility to perform a distributed cryogenic temperature monitoring, with a sub- μ K resolution. Thus, the application of superconducting S-SRRs, eventually benefiting from an even higher

Source: Superconductor Science and Technology

DOI: 10.1088/1361-6668/ae26d8