Study on broadband optical constants of yttrium fluoride thin films deposited by electron beam evaporation

In this paper, the broadband optical constants of YF3 thin films prepared by electron beam evaporation were studied (0.2 μm–14 μm), which are consistent with the data reported in other literature. The composite dispersion physical model of the optical constants of YF3 thin films was established by using Cody-Lorentz model and Gaussian oscillator model, which is employed in this study and is universal for YF3 thin films with water defects. The water absorption of the YF3 thin films occurs at 3251.9 cm−1 and 3454.3 cm-1 representing the symmetrical stretching vibration and asymmetric stretching vibration frequency of the HOH bond, and 1640.8 cm−1 representing the shear vibration frequency of the HOH bond. In addition, the Raman spectra of amorphous YF3 thin film shows that the intrinsic vibrational frequencies are 383 cm−1 and 462 cm−1. Based on the electron interband transition and the micro-structural vibration characteristics mentioned above, the broadband optical constants of the YF3 thin film are obtained, which makes up the deficiency of extinction coefficient data of YF3 thin film.