Origin of resolution enhancement by co-doping of scintillators: Insight from electronic structure calculations

Abstract

It was recently shown that the energy resolution of Ce-doped LaBr${}_3$ scintillator radiation detectors can be crucially improved by co-doping with Sr, Ca, or Ba. Here we outline a mechanism for this enhancement on the basis of electronic structure calculations. We show that (i) Br vacancies are the primary electron traps during the initial stage of thermalization of hot carriers, prior to hole capture by Ce dopants; (ii) isolated Br vacancies are associated with deep levels; (iii) Sr doping increases the Br vacancy concentration by several orders of magnitude; (iv) ${\text{Sr}}_{\text{La}}$ binds to $V_{\text{Br}}$ resulting in a stable neutral complex; and (v) association with Sr causes the deep vacancy level to move toward the conduction band edge. The latter is essential for reducing the effective carrier density available for Auger quenching during thermalization of hot carriers. Subsequent de-trapping of electrons from ${\text{Sr}}_{\text{La}}-V_{\text{La}}$ complexes then can activate Ce dopants that have previously captured a hole leading to luminescence. This mechanism implies an overall reduction of Auger quenching of free carriers, which is expected to improve the linearity of the photon light yield with respect to the energy of incident electron or photon.

References in corpus (6)

• Structure and optical properties of high light output halide scintillators
• First-Principles Studies of Luminescence in Ce doped Inorganic Scintillators
• Modeling the electrical conductivity in BaTiO3 on the basis of first-principles calculations
• Intrinsic point defects in aluminum antimonide
• Electronic structure of LaBr3 from quasi-particle self-consistent GW calculations
• Extrinsic point defects in aluminum antimonide

Cited by in corpus (4)

• Combinatorial approach to bulk detector material engineering: Application to rapid NaI performance optimization via multi-element doping/co-doping strategy
• A first-principles study of co-doping in lanthanum bromide
• Ionization-density-dependent Scintillation Pulse Shape and Mechanism of Luminescence Quenching in LaBr3:Ce
• Ab-initio prediction of fast non-equilibrium transport of nascent polarons in SrI${}_2$: A key to high-performance scintillation