Advanced optical spectroscopy of luminescent color centers in lithium fluoride thin films

Lithium fluoride, LiF, is a well-known dosimeter material. In thin films the direct use of optical absorption spectra to individuate the stable formation of different kinds of point defects is often precluded by the presence of interference fringes due to the refractive index difference between film and substrate. Photoluminescence measurements are more sensitive. Recently a very effective investigation method is developing: it is often called combined excitation–emission spectroscopy (CEES) in the literature. In this work we present the basic characteristics of this technique and the first results of the investigation of polycrystalline LiF films grown by thermal evaporation on fused silica substrates and gamma irradiated at several doses up to 10⁶ Gy in air.