Evaluation of Young's Modulus for Polymer Thin Film on Isotropic Substrate by Complex V(z) Curve

The complex reflectance function of acoustic waves in the incidence angle range from 0 to 60° was calculated for polymer thin films on glass substrates with different Young's modulus and density values. A characteristic phase change of the complex reflectance function was observed due to the existence of the polystyrene thin film on the glass substrate. The phase change appeared when the thickness of the polymer thin film was more than 0.9 µm at 300 MHz. The normalized wave number of the characteristic phase change varied sensitively with Young's modulus and the density of the polymer thin film. The contour map of the normalized wave number was obtained from these results. The determination method of Young's modulus of the polymer thin film by the characteristic phase change was proposed.