Critical Temperature tuning of Ti/TiN multilayer films suitable for low temperature detectors

TL;DR

This study explores the design of Ti/TiN multilayer films to precisely tune the critical temperature for low-temperature detectors, addressing uniformity and control issues in superconducting sensor fabrication.

Contribution

It demonstrates that critical temperature can be effectively tuned in Ti/TiN multilayers by adjusting layer thicknesses, offering a solution for improved superconducting detector performance.

Findings

Critical temperature tunable between 0.5 and 4.6 K

Superconducting transition controlled by layer thicknesses

High uniformity and quality factor achieved in multilayers

Abstract

We present our current progress on the design and test of Ti/TiN Multilayer for use in Kinetic Inductance Detectors (KIDs). Sensors based on sub-stoichiometric TiN film are commonly used in several applications. However, it is difficult to control the targeted critical temperature $T_C$, to maintain precise control of the nitrogen incorporation process and to obtain a production uniformity. To avoid these problems we investigated multilayer Ti/TiN films that show a high uniformity coupled with high quality factor, kinetic inductance and inertness of TiN. These features are ideal to realize superconductive microresonator detectors for astronomical instruments application but also for the field of neutrino physics. Using pure Ti and stoichiometric TiN, we developed and tested different multilayer configuration, in term of number of Ti/TiN layers and in term of different interlayer thicknesses. The target was to reach a critical temperature $T_C$ around $(1\div 1.5)$ K in order to have a low energy gap and slower recombination time (i.e. low generation-recombination noise). The results prove that the superconductive transition can be tuned in the $(0.5\div 4.6)$ K temperature range properly choosing the Ti thickness in the $(0\div 15)$ nm range, and the TiN thickness in the $(5\div 100)$ nm range