Comparison of Dielectric Loss in Titanium Nitride and Aluminum Superconducting Resonators

TL;DR

This study compares dielectric loss mechanisms in TiN and Al superconducting resonators, revealing dominant loss sources and effects of surface treatments on resonator quality factors.

Contribution

It provides a detailed comparison of dielectric loss contributions in TiN and Al resonators and demonstrates how surface treatments can improve quality factors.

Findings

Metal-air interface dominates loss in Al resonators.

Hydrofluoric acid etch reduces substrate-air interface loss in TiN.

Dielectric loss contributions vary significantly between TiN and Al devices.

Abstract

Lossy dielectrics are a significant source of decoherence in superconducting quantum circuits. In this report, we model and compare the dielectric loss in bulk and interfacial dielectrics in titanium nitride (TiN) and aluminum (Al) superconducting coplanar waveguide (CPW) resonators. We fabricate isotropically trenched resonators to produce a series of device geometries that accentuate a specific dielectric region's contribution to resonator quality factor. While each dielectric region contributes significantly to loss in TiN devices, the metal-air interface dominates the loss in the Al devices. Furthermore, we evaluate the quality factor of each TiN resonator geometry with and without a post-process hydrofluoric (HF) etch, and find that it reduced losses from the substrate-air interface, thereby improving the quality factor.