Yttrium fluoride (YF3) thin films with a thickness range of 10.8−1079.0 nm were prepared by electron beam evaporation. Spectroscopic ellipsometry was used to study the thickness-dependent optical properties of YF3 ultrathin films in the 300−820 nm wavelength range. With increasing thicknesses, the refractive indices of the intrinsic YF3 films increase slightly and approach that of bulk YF3 due to the decrease of void fractions. The effective refractive indices of the YF3 films also increase with increasing thicknesses, due to the surface and interface effects besides the contribution of decrease of void fractions.

中文翻译：

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氟化钇超薄膜在可见光波段的厚度依赖光学特性

通过电子束蒸发制备厚度范围为 10.8-1079.0 nm 的氟化钇 (YF3) 薄膜。光谱椭偏仪用于研究 YF3 超薄膜在 300-820 nm 波长范围内的厚度相关光学特性。随着厚度的增加，由于空隙率的降低，本征 YF3 薄膜的折射率略有增加，并接近块状 YF3 的折射率。YF3 薄膜的有效折射率也随着厚度的增加而增加，这是由于除了空隙率降低之外的表面和界面效应。