非晶-半导体/氧化物界面的悬挂键自旋弛豫和磁1/f噪声：理论
Dangling-bond spin relaxation and magnetic 1/f noise from the amorphous-semiconductor/oxide interface: Theory
摘要：
我们提出了一个磁噪声模型的基础上自旋翻转（而不是电子捕获）的顺磁性悬挂键在非晶半导体/氧化物界面。由单声子交叉弛豫机制导出了悬挂键与非晶界面隧穿二能级系统相互作用的自旋翻转时间的宽分布。温度和频率的依赖关系是敏感的三个能量尺度：悬挂键自旋塞曼能量δ，以及最小值（E_min）和最大值（E_max）的隧道二能级系统的能量分裂。我们比较并拟合我们的模型参数，以探测最近的实验锑施主注入核自旋自由硅自旋相干[T。Schenkel { \it等人}，应用物理信函88，112101（2006）]，并得出结论，10^{14}cm^{-2}数量级的悬挂键面积密度与数据一致。这使得能够预测单个自旋量子位相干时间作为与界面的距离和真实器件结构中的悬挂键区密度的函数。我们应用这个理论计算了Si/SiO_2衬底对SQUID器件的磁通量噪声的影响。我们对SQUID中通量噪声的显式估计导致在f= 1 Hz时噪声谱密度为10^{-12} Phi_{0} ^{2} {Hz}^{-1}的量级。这个值可以解释某些SQUID器件中磁通噪声的来源。最后，我们考虑使用表面钝化与氢，和剩余的核自旋噪声从一个完美的硅氢化物表面产生的抑制这些影响。
英文摘要：
We propose a model for magnetic noise based on spin-flips (not electron-trapping) of paramagnetic dangling-bonds at the amorphous-semiconductor/oxide interface. A wide distribution of spin-flip times is derived from the single-phonon cross-relaxation mechanism for a dangling-bond interacting with the tunneling two-level systems of the amorphous interface. The temperature and frequency dependence is sensitive to three energy scales: The dangling-bond spin Zeeman energy delta, as well as the minimum (E_min) and maximum (E_max) values for the energy splittings of the tunneling two-level systems. We compare and fit our model parameters to a recent experiment probing spin coherence of antimony donors implanted in nuclear-spin-free silicon [T. Schenkel {\it et al.}, Appl. Phys. Lett. 88, 112101 (2006)], and conclude that a dangling-bond area density of the order of 10^{14}cm^{-2} is consistent with the data. This enables the prediction of single spin qubit coherence times as a function of the distance from the interface and the dangling-bond area density in a real device structure. We apply our theory to calculations of magnetic flux noise affecting SQUID devices due to their Si/SiO_2 substrate. Our explicit estimates of flux noise in SQUIDs lead to a noise spectral density of the order of 10^{-12}Phi_{0}^{2} {Hz}^{-1} at f=1Hz. This value might explain the origin of flux noise in some SQUID devices. Finally, we consider the suppression of these effects using surface passivation with hydrogen, and the residual nuclear-spin noise resulting from a perfect silicon-hydride surface.
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