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在考虑探测光束光斑尺寸对调制光热反射(MPR)信号影响的基础上,建立了三维的薄膜-衬底体系的激光光热反射理论模型。对利用激光光热反射技术测量薄膜热物性的可行性进行了研究,并对影响调制光热反射信号的材料参数进行了分析。此外,通过数值模拟研究了多参数拟合问题,即利用调制光热反射频响信号同时确定薄膜热扩散率、衬底热扩散率和界面热阻这三个物理参数。结果表明,与已有的径向扫描方法相比,频率扫描方法中的这三个参数之间并不存在高度的相关性,因此采用频响信号进行多参数拟合,可提高多参数拟合的收敛性和精确性。
The laser photothermal reflection theoretical model of the three-dimensional thin film-substrate system was established based on the influence of the spot size of the probe beam on the modulated light-heat reflection (MPR) signals. The feasibility of using the laser photothermal reflection technique to measure the thermophysical properties of the films was studied. The material parameters that affected the modulation of the photothermal reflection signal were also analyzed. In addition, we study the multi-parameter fitting problem by numerical simulation, that is, the three physical parameters of film thermal diffusivity, substrate thermal diffusivity and interface thermal resistance are determined simultaneously by modulating the thermo-optical reflection signal. The results show that compared with the existing radial scanning method, there is not a high correlation between the three parameters in the frequency scanning method. Therefore, multi-parameter fitting by frequency response signal can improve multi-parameter fitting Convergence and accuracy.