Data underlying the publication: Characterization of low-loss hydrogenated amorphous silicon films for superconducting resonators

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, hydro- gen 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.

用于毫米-亚毫米（mm-submm）天文观测的超导电路元件，若能采用介电损耗与噪声均极低的沉积介质，将获得显著的性能提升。这将支持多层电路元件的应用，进而提升毫米-亚毫米滤波器的工作效率，并实现微波动电感探测器（microwave kinetic inductance detectors, MKIDs）的小型化。相较于晶体介质，非晶态介质会引入额外的损耗与噪声，其根源在于微观机制尚不明确的二能级系统缺陷。我们采用等离子体增强化学气相沉积法，在100℃、250℃及350℃的衬底温度下制备了氢化非晶硅薄膜。所测得的孔隙体积分数、氢含量、微观结构参数及键角无序度均与衬底温度呈负相关关系。在120毫开尔文、4至7吉赫兹的测试条件下，当谐振器能量为10^5个光子时，三款薄膜的损耗角正切均低于10^-5。这表明此类薄膜在MKIDs及片上毫米-亚毫米滤波器领域具备良好的应用前景。