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

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