Proximity-Coupled Ti/TiN Multilayers for use in Kinetic Inductance Detectors

TL;DR

This paper demonstrates the use of TiN/Ti multilayer films with tunable critical temperatures and high uniformity, suitable for advanced kinetic inductance detectors and quantum applications.

Contribution

It introduces a reproducible method to produce TiN/Ti multilayers with controlled Tc and high quality factors for superconducting detectors.

Findings

Achieved Tc tuning within 10 mK across a 75 mm wafer.

Produced films with high resistivity and quality factors exceeding 100k.

Demonstrated single photon detection at 1550 nm.

Abstract

We apply the superconducting proximity effect in TiN/Ti multi-layer films to tune the critical temperature, Tc, to within 10 mK with high uniformity (less than 15 mK spread) across a 75 mm wafer. Reproducible Tc's are obtained from 0.8 - 2.5 K. These films had high resistivities, > 100 uOhm-cm and internal quality factors for resonators in the GHz range on the order of 100k and higher. Both trilayers of TiN/Ti/TiN and thicker superlattice films were prepared, demonstrating a highly controlled process for films over a wide thickness range. Detectors were fabricated and showed single photon resolution at 1550 nm. The high uniformity and controllability coupled with the high quality factor, kinetic inductance, and inertness of TiN make these films ideal for use in frequency multiplexed kinetic inductance detectors and other potential applications such as nanowire detectors, transition edge sensors and associated quantum information applications.