LiF films: absorption and luminescence of colour centres

LiF films 1 μm thick have been produced by thermal evaporation on amorphous silica substrates. X-ray diffraction has shown the existence of a polycrystalline structure. The films were subjected at room temperature to electron beam irradiation of energy 3 keV and current 120 μA on anea of about 0.5 cm 2. This irradiation produced F 2 and F 3 + centres stable at room temperature that were observed by light absorption measurements. Although the concentration of the centres was much higher than that obtained usually in bulk crystals, luminescence was also observed.