论文标题
微米级传播长度的起源于无定形硅中的热声激发
Origin of micron-scale propagation lengths of heat-carrying acoustic excitations in amorphous silicon
论文作者
论文摘要
无定形硅的热携带声激发很感兴趣，因为它们的平均自由路径可能在室温下接近微米尺度。尽管进行了广泛的调查，但在热携带频率中弱声阻尼的起源仍然是辩论的话题。在这里，我们报告了使用瞬态光谱光谱法在60-315 K的无定形硅薄膜中的热导率的测量值。通过额外的皮秒声学测量，并考虑了玻璃中阻尼机制的已知频率依赖性，我们从$ \ sim 0.1-3 $ thz重建平均自由路径。平均自由路径与温度无关，并且在大多数此频率范围内都表现出瑞利散射趋势。观察到的趋势与基于正常模式分析的数值研究的预测不一致，但与其他眼镜上的不同测量相符。无定形SI中的微米级MFP是由于在次数THZ频率中缺乏Anharmonic或两级系统阻尼，从而导致携带热的声激发与室温下的室温阻尼，可与其他玻璃杯中的其他玻璃杯相当。
The heat-carrying acoustic excitations of amorphous silicon are of interest because their mean free paths may approach micron scales at room temperature. Despite extensive investigation, the origin of the weak acoustic damping in the heat-carrying frequencies remains a topic of debate. Here, we report measurements of the thermal conductivity mean free path accumulation function in amorphous silicon thin films from 60 - 315 K using transient grating spectroscopy. With additional picosecond acoustics measurements and considering the known frequency-dependencies of damping mechanisms in glasses, we reconstruct the mean free paths from $\sim 0.1-3$ THz. The mean free paths are independent of temperature and exhibit a Rayleigh scattering trend over most of this frequency range. The observed trend is inconsistent with the predictions of numerical studies based on normal mode analysis but agrees with diverse measurements on other glasses. The micron-scale MFPs in amorphous Si arise from the absence of anharmonic or two-level system damping in the sub-THz frequencies, leading to heat-carrying acoustic excitations with room-temperature damping comparable to that of other glasses at cryogenic temperatures.
