Preparation and characterization of aluminum oxide/aluminum fluoride mixture coatings for applications in the deep ultraviolet spectral range

In the present study the preparation and characterization of Al2O3/AlF3 material mixture coatings is described. The main focus is on the correlation between the optical properties (refractive index, extinction coefficient), elemental composition and mechanical properties, depending on deposition conditions. The thin mixture films prepared with E-Beam gun evaporation with and without plasma ion assistance show a continuous change in the refractive index between the basic materials extrema (n = 1.4 - 1.75), depending on the constituents volume filling factors. At the same time, extinction coefficients vary between less than 1x10(-4) and 2x10(-3). In addition, it can be shown that in dependency of the applied plasma ion assistance, the residual stress inside the mixture layers is tunable. Finally, several multilayer coatings has been prepared and investigated.