Effect of Ca colloids on in-situ ionoluminescence of CaF₂ single crystals

This work reports in-situ ion beam induced luminescence (IBIL) of CaF₂ crystals using 2-MeV proton excitation. The in-situ IBIL experiments were carried out at pelletron Tandem accelerator at the National Center for Physics, Islamabad, Pakistan. The spectrophotometry UV–Visible analysis revealed that proton beam induced Ca colloids. Their concentration increases with fluence, and the mean size reaches about 10 nm. The IBIL results showed a wide luminescence band extended from 230 to 450 nm and a new band at about 210 nm, attributed to the self-trapped exciton (STE) decay. It was found that the luminescence intensity increases linearly with dose. From the absorption measurements, indicating the colloid formation in CaF₂ by proton irradiation, we believe that the latter colloids are responsible for the luminescence improvement during proton beam irradiation.