Speaker
Description
Superconductor-Insulator-Superconductor multilayers improve the performance of SRF cavities providing magnetic screening of the bulk cavity and lower surface resistance.
In this framework NbTiN mixtures stand as a potential material of interest combining the excellent superconducting properties of NbN with the good metallic and structural properties of TiN. One method which enables fine tuning of the stoichiometry and precise thickness control in sub-nm range is atomic layer deposition (ALD). ALD bases on a sequence of self-limiting gas-solid surface reactions and allows for uniform coating of complex geometries.
In this talk, we report about $Nb_{0.66}Ti_{0.33}N$ thin films deposited by plasma-enhanced ALD on insulating AlN buffer layer, which has been previously deposited in situ without vacuum break with the same technique. The deposition process has been optimized by studying the superconducting electrical properties of the films. Post-deposition thermal annealing studies with varying temperatures, annealing times, and gas atmospheres have been performed to further improve the thin film quality and the superconducting properties. Our experimental studies show an increase in $T_{c}$ by 87.5% after thermal annealing and a maximum $T_{c}$ of 13.9 K has been achieved for $Nb_{0.66}Ti_{0.33}N$ of 23 nm thickness. Future steps include lattice characterization, using XRR/XRD/EBSD/PALS, and SRF measurements to obtain $H_{c1}$ and the superconducting gap $\Delta$.
