多层薄膜瞬态热弹反射光栅实验及其理论分析和有限元数值计算

Transient thermal grating measurements and FEM calculations of thermoelastic theory for characterizing multilayered thin films

多层薄膜/基片材料的热学性质受各层薄膜及基片的共同影响,因此同时评估各层材料的热学性质是非常重要的。激光诱导瞬态热栅技术是一种研究材料表面及亚表面光声光热现象有效的方法,因此可用于研究多层材料的热学性质。本文利用瞬态热弹反射光栅方法研究多层薄膜/基片结构材料的热扩散率,首先对Al/ZnO/Si基片结构的多层材料进行激光诱导瞬态热栅的光衍射检测实验,然后通过对该瞬态热栅的光衍射强度信号进行理论分析及有限元数值模拟,得到Al/ZnO/Si各层热扩散率对其表面温度场分布的影响,进而计算铝膜和氧化锌膜热扩散率对瞬态热栅引起衍射光信号的贡献。最后将理论分析与实验结果进行多参数拟合,在基片的参量已知的情况下,可同时得到铝膜和氧化锌膜的热扩散率。

Thermal properties of multilayered thin films deposited on substrates are influenced by each layer,so it is important to estimate simultaneously the property of each layer of them.Laser induced transient thermal grating technique provides higher sensitivity and depth resolution in photothermal and photoacoustic investigations for spatially restricted areas near surface.In this paper,the thermal diffusivities of bilayered thin films with nanoscaled thickness deposited on substrates are characterized by transient grating method.Based on the experimental results of the laser induced transient thermal grating technique,a two-dimensional thermal diffusivity model and finite element method are proposed to calculate the thermal diffusivities of the trilayered structures.By fitting the theoretical calculations to the experimental data of a series of trilayered structures of Al/ZnO/Si with different thicknesses of ZnO films,the thermal diffusivities of the Al and ZnO films can be evaluated simultaneously.