Low two-level-system noise in hydrogenated amorphous silicon

At sub-kelvin temperatures, an excess frequency noise is generated by two-level-systems (TLSs) defects existing inside amorphous dielectrics, degrading the performance of a wide range of devices using superconductive resonators such as qubits or kinetic inductance detectors. We report here on measurements of TLS noise in hydrogenated amorphous silicon (a-Si:H) films deposited by plasma-enhanced chemical vapor deposition in superconducting lumped-element resonators using parallel-plate capacitors. The TLS noise results presented in this article for two recipes of a-Si:H improve on the best achieved in the literature by a factor of 8 – 80 for a-Si:H and other amorphous dielectrics, and are comparable to that observed with crystalline dielectrics.