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Origin of the 420nm Absorption Band and Effect of Doping Fluorine in PbWO4 Crystals |
| TAO Kun;ZHANG Qi-Ren;LIU Ting-Yu;ZHANG Fei-Wu |
| College of Science, University of Shanghai for Science and Technology, Shanghai 200093 |
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| Cite this article: |
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TAO Kun, ZHANG Qi-Ren, LIU Ting-Yu et al 2005 Chin. Phys. Lett. 22 215-218 |
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Abstract The electronic structures for three types of PbWO4 (PWO) crystals, the perfect PWO, the PWO containing lead vacancy (PWO-Vpb) and fluorine doped PWO crystal (F-:PWO), are systematically studied within the framework of density functional theory. The computational results show that the Pb 6s state situates below the valence band so that Pb2 ions are unable to trap holes forming Pb3+ or Pb4+ to compensate for Vpb2-. The hole-trappers in PWO-Vpb are O2- ions. Two of the longer-bond O2- ions share a hole forming O23-, and four of the longer-bond oxygen ions trap two holes forming an associated color centre [O23--Vpb-O23-], which may be the origin of the 420nm absorption band. It is also concluded that the doping of F- would reduce the band gap and F- ions substituting for O2- can effectively restrict the formation of [O23--Vpb-O23-] and weaken the 420nm absorption band and hence enhance the scintillation property of PWO.
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| Keywords:
76.30.Mi
74.62.Dh
71.20.-b
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Published: 01 January 2005
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| PACS: |
76.30.Mi
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(Color centers and other defects)
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74.62.Dh
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(Effects of crystal defects, doping and substitution)
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71.20.-b
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(Electron density of states and band structure of crystalline solids)
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