Superconducting high kinetic inductance films for quantum circuits

High-kinetic inductance disordered superconductors are gaining growing interest in the scientific community, especially for applications in the field of cQED and quantum sensing. Thin films offer the possibility to tune the inductance by optimising the chemical composition and the crystalline properties of the film, which depend on the deposition process. Tunable kinetic inductance values enable the exploration of a wide range of couplings between different elements in quantum circuits. Moreover, high-kinetic inductance resonators or artificial transmission lines can be exploited to achieve compact read-out devices and quantum circuits. In the framework of the DART WARS experiment, we have developed high-kinetic inductance thin NbTiN films for the microfabrication of low-noise and high dynamic range Kinetic Inductance Traveling Wave Parametric Amplifiers (KI-TWPAs). We present the optimisation of the deposition process via rf sputtering with a Nb80%Ti20% target, in order to reach high control on the film characteristics. The parameter landscape related to the different sputtering conditions, such as pressure, power and nitrogen flow has been explored and the thickness of the film has been exploited as fine-tuning parameter to adjust the kinetic inductance and critical temperature values. Besides the microfabrication of KI-TWPA devices, the optimised NbTiN films find direct applications for the development of a wide range of quantum technologies, such as Kinetic Inductance Detectors (KIDs), high-kinetic inductance resonators and superconducting nanowires.