Lattice location and ionic state of Tm ions implanted into CaF2

Tm+ ions with energy 100 KeV were implanted into (111)-cut CaF2 single crystals at 90 K and room temperature (RT). Ion channeling analysis has revealed that almost all the implanted Tm ions occupy the substitutional sites replacing Ca2+. In order to detect the ionic state of Tm we have tried to apply the 200 KeV Ar+-beam induced luminescence and observed intense two broad emission peaks in the visible region originating from Tm2+ in CaF2. Such a heavy ion-induced luminescence is different from the emission subsequent to the absorption of ultraviolet light. The optical absorption measurement has shown that about 80% of the implanted Tm ions exists as divalent state. (author)