Two-level systems (TLS) are an important, if not dominant, source of loss and noise for superconducting resonators such as those used in kinetic inductance detectors and some quantum information science platforms. They are similarly important for loss in photolithographically fabricated superconducting mm-wave/THz transmission lines. For both lumped-element and transmission-line structures, native amorphous surface oxide films are typically the sites of such TLS in nonmicrostripline geometries, while loss in the (usually amorphous) dielectric film itself usually dominates in microstriplines. We report here on the demonstration of low TLS loss at GHz frequencies in hydrogenated amorphous silicon (a-Si:H) films deposited by plasma-enhanced chemical vapor deposition in superconducting lumped-element resonators using parallel-plate capacitors (PPCs). The values we obtain from two recipes in different deposition machines, $7\times {10}^{-6}$ and $12\times {10}^{-6}$, improve on the best achieved in the literature by a factor of 2–4 for a-Si:H and are comparable to recent measurements of amorphous germanium. Moreover, we have taken care to extract the true zero-temperature, low-field loss tangent of these films, accounting for temperature and field saturation effects that can yield misleading results. Such robustly fabricated and characterized films render the use of PPCs with deposited amorphous films a viable architecture for superconducting resonators and they also promise extremely low loss and high quality factor for photolithographically fabricated superconducting mm-wave/THz transmission lines used in planar antennas and resonant filters.

中文翻译：

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氢化非晶硅低电场和零温两能级系统损耗表征

对于超导谐振器（例如用于动感电感探测器和一些量子信息科学平台的超导谐振器）来说，两级系统（TLS）即使不是主要的，也是一个重要的损耗和噪声源。它们对于光刻制造的超导毫米波/太赫兹传输线的损耗同样重要。对于集总元件和传输线结构，原生非晶表面氧化膜通常是非微带线几何结构中此类 TLS 的位置，而（通常是非晶）介电膜本身的损耗通常在微带线中占主导地位。我们在这里报告了使用平行板电容器 (PPC) 在超导集总元件谐振器中通过等离子体增强化学气相沉积沉积的氢化非晶硅 (a-Si:H) 薄膜在 GHz 频率下的低 TLS 损耗。我们从不同沉积机的两种配方中获得的值，$7\times {10}^{-6}$和$12\times {10}^{-6}$，将 a-Si:H 文献中取得的最佳结果提高了 2-4 倍，并且与最近对非晶锗的测量结果相当。此外，我们还小心地提取了这些薄膜的真实零温度、低场损耗角正切，考虑了可能产生误导性结果的温度和场饱和效应。这种坚固耐用的制造和表征薄膜使得使用沉积非晶薄膜的 PPC 成为超导谐振器的可行架构，并且它们还为平面天线和谐​​振滤波器中使用的光刻制造的超导毫米波/太赫兹传输线提供了极低的损耗和高质量因数。