RADIATION-DAMAGE IN TB-IMPLANTED CAF2 OBSERVED BY CHANNELING AND LUMINESCENCE MEASUREMENTS

The effects of 100 keV Tb ion implantation in CaF2 single crystals have been investigated using Rutherford backscattering/channeling technique and luminescence spectra during ion implantation, depending on ion doses. Terbium ions were implanted into (111)-cut CaF2 single crystals in random directions with doses ranging from 1 x 10(13) to 1 x 10(17) Tb+/cm2 at -100-degrees-C, 25-degrees-C and 100-degrees-C. The luminescence signals were measured by 100 keV Ar ion beam irradiation at room temperature to Tb-implanted specimens in order to detect the ionic state of Th. Two broad emission peaks (near 380 and 545 nm) in visible regions were observed, originating from Tb3+ in CaF2. The same luminescence was also observed even during Tb implantation to CaF2. The luminescence near 380 nm is identified as an emission of 5D3-->F-7(6) and that near 545 nm is 5D4-->F-7(5). The emission peak intensities depend on ion dose. Channeling measurements suggest that most of the Tb atoms occupy substitutional lattice sites. Intensities of luminescence and Tb depth profiles depend on the target temperature. In conclusion, implanted Th atoms occupy Ca lattice sites and emit green luminescence light.