Characterization of low-loss hydrogenated amorphous silicon films for superconducting resonators
Bruno T. Buijtendorp (TU Delft - Tera-Hertz Sensing)
Juan Bueno (SRON–Netherlands Institute for Space Research)
David J. Thoen (TU Delft - Tera-Hertz Sensing)
Vignesh Murugesan (SRON–Netherlands Institute for Space Research)
Paolo M. Sberna (TU Delft - Tera-Hertz Sensing, TU Delft - EKL Processing)
Jochem J.A. Baselmans (TU Delft - Tera-Hertz Sensing, SRON–Netherlands Institute for Space Research)
Sten Vollebregt (TU Delft - Electronic Components, Technology and Materials)
Akira Endo (TU Delft - Tera-Hertz Sensing)
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Abstract
Superconducting circuit elements used in millimeter-submillimeter (mm-submm) astronomy would greatly benefit from deposited dielectrics with small dielectric loss and noise. This will enable the use of multilayer circuit elements and thereby increase the efficiency of mm-submm filters and allow for a miniaturization of microwave kinetic inductance detectors (MKIDs). Amorphous dielectrics introduce excess loss and noise compared with their crystalline counterparts, due to two-level system defects of unknown microscopic origin. We deposited hydrogenated amorphous silicon films using plasma-enhanced chemical vapor deposition, at substrate temperatures of 100°C, 250°C, and 350°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 105 photons, at 120 mK and 4 to 7 GHz. This makes these films promising for MKIDs and on-chip mm-submm filters.