Characterization of Silver-Doped LiF Crystal Grown by Czochralski Technique for Dark Matter Search Application

In this article, the growth, luminescence, and scintillation properties of a silver-doped LiF crystal grown by the Czochralski technique are studied. The absorption spectrum of the crystal is measured at room temperature and optical energy bandgap of the crystal is calculated as 5.2 eV. The luminescence and scintillation properties of the crystal are studied at different temperatures (10-550 K) under the excitations with X-ray, 266-nm laser, 280-nm light emitting diode (LED), and 90Sr beta source. The crystal shows a violet emission (405 nm) under the excitation of a 280-nm LED source. The luminescence decay time of the crystal is measured from room temperature (300 K) to 10 K under the excitation of the 266-nm laser source. The decay time curves are fit with 2-exponential (300-200 K) and 3-exponential (175-10 K) decay functions. The shortest (27.2μs) and the longest decay time (42.8μs) of the crystal are obtained at 300 and 75 K, respectively. Thermoluminescence (TL) measurements were carried out from 10 to 300 K and 325 to 550 K in order to investigate the presence of trap centers. The different kinematic parameters such as order of kinematics, trap depth, and frequency factor are calculated for the observed TL peaks. The scintillation light yield of the crystal is measured with a continuous single photon counting technique using a 90Sr beta source in the temperature range from 300 to 10 K. In this article, we will emphasize the potentiality of a Li-based crystal for dark matter search applications.