Titanium Nitride Films for Ultrasensitive Microresonator Detectors

TL;DR

This paper explores titanium nitride films' properties, demonstrating their suitability for ultrasensitive superconducting microresonator detectors with low loss, high responsivity, and long quasiparticle lifetimes.

Contribution

It provides a detailed analysis of TiN films' properties and their advantages for microresonator detectors, highlighting their low loss and potential for high sensitivity.

Findings

TiN films exhibit very low loss (Q_i > 10^7).

Quasiparticle lifetimes in TiN microresonators range from 10 to 200 microseconds.

TiN-based detectors are predicted to achieve sensitivities below 10^-19 WHz^(-1/2).

Abstract

Titanium nitride (TiNx) films are ideal for use in superconducting microresonator detectors because: a) the critical temperature varies with composition (0 < Tc < 5 K); b) the normal-state resistivity is large, \rho_n ~ 100 $\mu$Ohm cm, facilitating efficient photon absorption and providing a large kinetic inductance and detector responsivity; and c) TiN films are very hard and mechanically robust. Resonators using reactively sputtered TiN films show remarkably low loss (Q_i > 10^7) and have noise properties similar to resonators made using other materials, while the quasiparticle lifetimes are reasonably long, 10-200 $\mu$s. TiN microresonators should therefore reach sensitivities well below 10^-19 WHz^(-1/2).