Microwave properties of superconducting atomic-layer deposited TiN films

TL;DR

This study investigates the microwave properties of superconducting TiN films grown by atomic layer deposition, revealing high quality factors and tunable electrodynamic responses influenced by film resistivity and thickness.

Contribution

It demonstrates the ability to tune superconducting and microwave properties of TiN films via atomic layer deposition and models their response with a modified quasiparticle density of states.

Findings

Internal quality factors above one million.

High sheet inductances up to 620 pH.

Pulse response times up to 100 microseconds.

Abstract

We have grown superconducting TiN films by atomic layer deposition with thicknesses ranging from 6 to 89 nm. This deposition method allows us to tune the resistivity and critical temperature by controlling the film thickness. The microwave properties are measured, using a coplanar-waveguide resonator, and we find internal quality factors above a million, high sheet inductances (5.2-620 pH), and pulse response times up to 100 \mu s. The high normal state resistivity of the films (> 100 \mu\Omega cm) affects the superconducting state and thereby the electrodynamic response. The microwave response is modeled using a quasiparticle density of states modified with an effective pair-breaker,consistently describing the measured temperature dependence of the quality factor and the resonant frequency.