Epitaxial titanium nitride microwave resonators: Structural, chemical, electrical, and microwave properties

TL;DR

This study investigates epitaxial titanium nitride thin films on sapphire, demonstrating their excellent structural, chemical, and microwave properties, and achieving high-quality factors in superconducting microwave resonators for quantum circuits.

Contribution

It provides a comprehensive characterization of epitaxial titanium nitride films and demonstrates their potential for low-loss superconducting quantum circuits.

Findings

Achieved a maximum internal quality factor of 3.3×10^6 at low temperatures.

Measured microwave loss-tangent comparable to best reported values.

Established epitaxial titanium nitride as a promising material for quantum-circuit applications.

Abstract

Titanium nitride is an attractive material for a range of superconducting quantum-circuit applications owing to its low microwave losses, high surface inductance, and chemical stability. The physical properties and device performance, nevertheless, depend strongly on the quality of the materials. Here we focus on the highly crystalline and epitaxial titanium nitride thin films deposited on sapphire substrates using magnetron sputtering at an intermediate temperature (300$^{\circ}$C). We perform a set of systematic and comprehensive material characterization to thoroughly understand the structural, chemical, and transport properties. Microwave losses at low temperatures are studied using patterned microwave resonators, where the best internal quality factor in the single-photon regime is measured to be $3.3\times 10^6$, and $> 1.0\times 10^7$ in the high-power regime. Adjusted with the material filling factor of the resonators, the microwave loss-tangent here compares well with the previously reported best values for superconducting resonators. This work lays the foundation of using epitaxial titanium nitride for low-loss superconducting quantum circuits.