Czochralski growth of UV-grade CaF2 single crystals using ZnF2 additive as scavenger

Abstract CaF 2 single crystals suitable for excimer laser application in the ultraviolet range were grown by the Czochralski method. ZnF 2 additive and CF 4 gas were successfully used as scavengers for removing the water molecules in the growth environment, which otherwise cause various defects such as subgrain boundaries, bubbles and oxygen-related precipitates in the CaF 2 crystal. Czochralski-grown CaF 2 crystals had very good crystallinity and a high transmittance in the wavelength range of the ultraviolet laser. The defect structures of colored and colorless CaF 2 crystals were compared.