Plasma ion assisted deposition of aluminium oxide and aluminium oxifluoride layers for applications in the ultraviolet spectral range

Plasma ion assisted deposition of alumina coatings under optimized conditions results in superior UV optical coating properties. A further increase in the UV transparency can be achieved when adding fluorine as reactive gas during deposition. [Display omitted] ► Alumina and aluminium oxifluoride layers can be prepared by PIAD techniques. ► Thermoprobe measurements quantify the energy impact on the substrate. ► Layer properties can be tuned by the reactive gas flow during deposition. ► Aluminium oxifluoride layers show a better UV transparency than alumina layers. We present extended experimental material about optical and mechanical properties as well as the water content of aluminium oxide films, deposited by plasma ion assisted electron beam evaporation. A clear correlation between these experimental data is established and understood as being affected by the different degree of the porosity of the films. When adding fluorine as a reactive gas during deposition, aluminium oxifluoride layers can be obtained that appear nearly free of water, and combine UV-transparency with higher UV refractive indices than porous aluminium oxide layers.