Study of temperature annealing induced optical absorption and structural disorder in CaF2 single crystals irradiated with Xe132 heavy ions

Abstract

This article studies radiation processes in calcium fluoride (CaF₂) single crystals irradiated with 230 MeV Xe¹³² heavy ions. The study utilized absorption spectroscopy and thermal activation spectroscopy. The effect of thermal annealing on structural changes and optical absorption caused by radiation defects was studied. CaF₂ samples were subjected to step-by-step heating to temperatures from 295 K to 1023 K, which made it possible to trace the dynamics of crystal structure restoration and changes in optical characteristics. The experimental results on optical spectroscopy were analyzed in Tauc and Urbach coordinates. The results show that with increasing annealing temperature, the intensity of absorption bands decreases, indicating recombination of defect centers and a decrease in structural disorder. It was also revealed that at temperatures above 800 K, an increase in the Urbach energy and a shift in the fundamental absorption edge are associated with the formation of new structural defects. The work provides new data on the mechanisms of formation and evolution of radiation defects in ion-irradiated materials and opens up prospects for increasing the radiation resistance of CaF₂-based optical materials.