Origin of resolution enhancement by co-doping of scintillators: Insight from electronic structure calculations
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)
- Department of Applied Physics, Chalmers University of Technology, Gothenburg (Sweden)
It was recently shown that the energy resolution of Ce-doped LaBr{sub 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) Sr{sub La} binds to V{sub 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 Sr{sub La}–V{sub Br} complexes 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.
- OSTI ID:
- 22300277
- Journal Information:
- Applied Physics Letters, Vol. 104, Issue 21; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CAPTURE
CARRIER DENSITY
CERIUM ADDITIONS
COMPUTERIZED SIMULATION
DOPED MATERIALS
ELECTRONIC STRUCTURE
ELECTRONS
ENERGY RESOLUTION
HOLES
LANTHANUM BROMIDES
LUMINESCENCE
PHOSPHORS
PHOTONS
QUENCHING
RADIATION DETECTORS
THERMALIZATION
TRAPS
VACANCIES
VISIBLE RADIATION