Investigation of thin fluoride films for optical applications by surface analytical methods and electron microscopy

Impurity contents of loosely packed CaF2 and LaF3 films are analysed by SNMS depth-profiling. On the basis of TEM investigations a quantitative description of the structure of the films is given. The irreversibly incorporated oxygen contents of the films are nearly independent of the film structures. In contrast, the irreversibly incorporated carbon contents are proportional to the inner surfaces of the loosely packed films and to the C-contaminations of appropriate surfaces of compact fluoride samples. It is concluded that the irreversibly incorporated C covers the grain surfaces and the irreversibly incorporated C is located preferably within the grains.