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 μOhm 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 μs. TiN microresonators should therefore reach sensitivities well below 10^-19 WHz^(-1/2).
@article{arxiv.1003.5584,
title = {Titanium Nitride Films for Ultrasensitive Microresonator Detectors},
author = {Henry G. Leduc and Bruce Bumble and Peter K. Day and Anthony D. Turner and Byeong Ho Eom and Sunil Golwala and David C. Moore and Omid Noroozian and Jonas Zmuidzinas and Jiansong Gao and Benjamin A. Mazin and Sean McHugh and Andrew Merrill},
journal= {arXiv preprint arXiv:1003.5584},
year = {2015}
}