Characterization of low-loss hydrogenated amorphous silicon films for superconducting resonators

TL;DR

This study investigates hydrogenated amorphous silicon films deposited at various temperatures, demonstrating their low dielectric loss and potential for use in superconducting resonators for astronomical applications.

Contribution

It provides a detailed characterization of hydrogenated amorphous silicon films deposited at different temperatures, highlighting their low dielectric loss suitable for superconducting resonators.

Findings

All films have a loss tangent below 10^-5 at 120 mK and 4-7 GHz.

Lower substrate temperatures result in higher void volume and hydrogen content.

Films are promising for microwave kinetic inductance detectors and millimeter-wave filters.

Abstract

Superconducting resonators used in millimeter-submillimeter astronomy would greatly benefit from deposited dielectrics with a small dielectric loss. We deposited hydrogenated amorphous silicon films using plasma-enhanced chemical vapor deposition, at substrate temperatures of 100\deg C, 250\deg C and 350\deg C. The measured void volume fraction, hydrogen content, microstructure parameter, and bond-angle disorder are negatively correlated with the substrate temperature. All three films have a loss tangent below $10^{-5}$ for a resonator energy of $10^5$ photons, at 120 mK and 4-7 GHz. This makes these films promising for microwave kinetic inductance detectors and on-chip millimeter-submilimeter filters.