Self‐Trapped Particles in Complex Oxide Crystals

Abstract

Self-trapped hole (STH) and self-trapped exciton (STE) states which are formed in Y3AI5Ol2, Y,SiO,, and TR,Si,O, crystals under y-irradiation in the temperature interval of 77 to 200 K are investigated. The STH is shown to be molecular 0;-, absorbing a t 1.6 eV (for Y,A1501z) and a t 1.65 eV (for Y,SiO,) and causing the eleven-component EPR signal ; the corresponding S!I' E emits a t 3.9 and 3.6 eV. In metal-doped crystals the exciton and hole delocalization lead to a decreasing of the emission energy, to a short-wave shift of the absorption band, and to the growth of the anneal temperature. At the self-localization temperature excitons are proved to migrate by jump diffusion and to transfer energy to the impurity ions exciting their emission.

Photoluminescence and scintillation properties of Pr-doped (Lu, Y)2Si2O7 crystals

“…This was considered to be derived from the recombination of self-trapped excitons (STE) because undoped LPS showed the emissions with similar spectral features at the same ranges under 150 nm excitation and γ-rays exposure. 49,50) Figure 6 shows the X-ray-induced scintillation decay curves of Pr-doped LYPS. They were composed of a sum of two exponential functions when deconvoluted the IRF.…”

Bright and ultra-fast scintillation from a semiconductor?

“…The result is called a self-trapped hole that forms rapidly during thermalization. The self-trapped holes can attract ionization electrons to become self-trapped excitons that are usually quenched at room temperature [6, 7]. The unpaired spin associated with the hole and the diffuse electron spin form a triplet state which has a radiative lifetime of typically 10 −6 s because the transition is spin forbidden [8].…”

“…Semiconductors have an advantage over ionic crystals in that ionization holes do not spontaneously self-trap by lattice deformation [6, 7] but can bind with ionization electrons to form free excitons and those in turn can bind to defects such as donors, acceptors, or isoelectronic ions [36]. Their radiative recombination can produce efficient near band edge scintillation that can also be ultra-fast in the case of direct gap semiconductors.…”

Silicate Glass-Based Nanocomposite Scintillators

“…Single crystals of these orthosilicate materials were prepared by the Czochralski method using radio-frequency (RF) heating due to very high melting point of these compounds (between ~1950-2150 0 C) (Melcher et al, 1993). The growth of single crystals of another stoichiometry in the SiO 2 -RE 2 O 3 system, namely RE 2 Si 2 O 7 , was reported also in early 1980's and basic optical and luminescence characteristics were explored (BretheauRaynal et al, 1980;Vakhidov et al, 1981). However, scintillation characteristics of Ce-doped single crystals of Lu 2 Si 2 O 7 (LPS) started to be studied only in last decade (Pauwels et al, 2000).…”