VUV excited luminescence and thermoluminescence investigation on Er~(3+)- or Pr~(3+)-doped BaY_2F_8 single crystals

摘要

Photoluminescence (PL), thermoluminescence (TL) emission spectra and TL glow curves of barium yttrium fluoride (BaY2F8-BaYF), undoped and doped with erbium (Er3+) or praseodymium (Pr3+) were measured to investigate the fundamental absorption (band gap E-g), the nature of the trapping centers, as well as the electronic transitions of Ln(3+) in BaYF host. The band gap energy E-g of BaY2F8 was determined by vacuum ultraviolet (VIJV) excitation measurements to be around 11.2 eV. Additionally, the electronic transition from excited states of Ln(3+) ions and the exciton state were also identified. TL emission spectra showed that the TL emission of doped samples is related to the Ln(3+) ion, indicating that the related host trapping centers are not affected by the new trapping centers originated due the dopant ions. Trap depths were calculated by fitting the glow curves using a first order kinetics model. Host-related trapping centers were attributed to intrinsic defects such as V-k and F centers and the new TL peaks observed for Er- and Pr-doped samples was associated to the electrons trapping centers. These results lead us to propose a simple model to explain the origin of the TL emission in BaYF.