三层共振介电纳米薄膜弹性常数的皮秒超声研究
Elastic constant of dielectric nano-thin films using three-layer resonance studied by picosecond ultrasonics
摘要：
纳米级薄膜的弹性常数和声速是设计声滤波器的基础。然而，对于介电薄膜，测量它们是困难的。在这项研究中，我们使用一个三层结构，其中一个介电纳米薄膜夹在较厚的金属膜来测量的纵向弹性常数的电介质膜。我们提出了一个效率函数来估计组件的最佳厚度。我们使用Pt/NiO/Pt三层膜来验证我们提出的方法。在室温下沉积的NiO的弹性常数比体值小$\sim$ 40 $\%$。然而，随着沉积温度的升高，它接近体值。我们还发现，铂膜的弹性常数的不确定性不显着地影响在这种结构中的NiO的弹性常数的测定的准确性。
英文摘要：
Elastic constants and sound velocities of nm-order thin films are essential for designing acoustic filters. However, it is difficult to measure them for dielectric thin films. In this study, we use a three-layer structure where a dielectric nano-thin film is sandwiched between thicker metallic films to measure the longitudinal elastic constant of the dielectric film. We propose an efficiency function to estimate the optimal thicknesses of the components. We use Pt/NiO/Pt three-layer films for confirming our proposed method. The determined elastic constant of NiO deposited at room temperature is smaller than the bulk value by $\sim$40$\%$. However, it approaches the bulk value as the deposition temperature increases. We also reveal that uncertainty of the elastic constant of the Pt film insignificantly affects the accuracy of the determined elastic constant of NiO in this structure.
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