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Title: DX-like centers in NaI:Tl upon aliovalent codoping

Aliovalent doping has been recently shown to remarkably improve energy resolution in some halide scintillators. Based on first-principles calculations we report on the formation of DX-like centers in a well-known scintillator material, Tl-doped NaI (NaI:Tl), when codoped with Ca or Ba. Our calculations indicate a net binding energy favoring formation of the defect complex (Tl{sub Na}{sup −}+Ca{sub Na}{sup +}) involving a new cation-cation bond, instead of the isolated substitutional defects. The pair has properties of a deep DX-like acceptor complex. Doping with the aliovalent anion impurity Te is also found to induce deep centers, which can act as effective electron or hole traps. The hole trapped as Te{sub I}{sup 0} involves large lattice relaxation of the Te and an adjacent iodine, consistent with extrinsic self-trapping of the hole. Thus, in contrast to the positive effect achieved by aliovalent co-doping of the rare-earth tri-halides LaBr{sub 3}:Ce and CeBr{sub 3}:Ca as reported recently, co-doping with donor-like cations Ca, Ba, or the acceptor-like anion Te in monovalent NaI:Tl is found to inhibit scintillation response.
Authors:
;  [1] ; ;  [2] ;  [3]
  1. Department of Chemistry and Physics, Arkansas State University, State University, Arkansas 72467 (United States)
  2. Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27106 (United States)
  3. Department of Physics, Fisk University, Nashville, Tennessee 37208 (United States)
Publication Date:
OSTI Identifier:
22402766
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANIONS; BINDING ENERGY; CATIONS; CERIUM BROMIDES; DOPED MATERIALS; ELECTRONS; ENERGY RESOLUTION; HOLES; IMPURITIES; IODINE; LANTHANUM BROMIDES; RARE EARTHS; RELAXATION; SCINTILLATIONS; SODIUM IODIDES; TRAPPING; TRAPS