Low-temperature spectroscopic and scintillation characterisation of Ti-doped Al2O3

The luminescence properties of Ti-doped Al2O3 crystals have been studied using monochromatic VUV and X-ray radiation in the temperature range 9-300 K. In addition to the emission band of Ti3+ in the near IR region and blue emission at 420 nm that are commonly observed in this material, we detected a UV band at 290 nm which contributes approximately one-third to the integrated emission under X-ray excitation. Based on the results of the study this band was assigned to the radiative decay of excitons localised at activator ions. Particular attention has been given to the assessment of the feasibility of the material as cryogenic scintillation detector. The low-temperature scintillation light yield of Al2O3-Ti (0.20 wt%) is found to be 2300±200 ph/MeV at 32 keV and an estimate shows that it is two times larger for a sample with 0.07 wt% of activator. Given this, we concluded that Ti-doped Al2O3 appears to be very suitable material for cryogenic Dark Matter search experiments that rely on the simultaneous detection of phonon and scintillation signals.