Proton irradiation-induced defect aggregation and metallic nanoparticles in CaF2 single-crystal

Abstract

Proton irradiation induced-defects aggregation and metallic nanoparticles in single-crystal CaF2 was investigated by X ray diffraction (XRD), Raman spectroscopy and UV–Vis spectrophotometry. The structural reports reveal the degradation of material crystallinity after irradiation without amorphization, as a result of generated anion point defects (F- and H-center pairs). Particularly, Raman analysis reveals the colloids formation and even the increase of their size with increasing energy. While confirming this result, the optical measurements show an anticorrelation between the concentration of F-centers and Ca colloids with increasing proton fluence. The blue shift of the colloid band, observed at higher energies, indicates that larger colloids are formed at deeper penetration, resulting in the development of a compressive stress in material