VUV excited luminescence and thermoluminescence investigation on Er3+- or Pr3+-doped BaY2F8 single crystals

Abstract

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 – Eg), the nature of the trapping centers, as well as the electronic transitions of Ln3+ in BaYF host. The band gap energy Eg of BaY2F8 was determined by vacuum ultraviolet (VUV) excitation measurements to be around 11.2 eV. Additionally, the electronic transition from excited states of Ln3+ ions and the exciton state were also identified. TL emission spectra showed that the TL emission of doped samples is related to the Ln3+ 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 Vk 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.