253 research outputs found
Defects and persistent luminescence in Eu-doped SrAlO
We investigate native point defects and rare-earth (co)dopants in
SrAlO using hybrid density-functional defect calculations. Europium
(Eu) and dysprosium (Dy) are found to be mixed valence and energetically most
favorable at the Sr lattice sites. However, unlike Eu where both Eu and
Eu can be realized in synthesis, Dy is stable predominantly as
Dy, and the divalent Dy may only be photogenerated under
irradiation. On the basis of an analysis of Eu-related band-defect (including
charge-transfer) and interconfigurational - optical transitions, we
assign the characteristic broad blue (445 nm) and green (520 nm) emission bands
in Eu-doped SrAlO to the
transition in Eu incorporated at the Sr1 and Sr2 sites, respectively.
Strontium interstitials (not oxygen vacancies, in contrast to what is commonly
believed) and Dy can act as efficient electron traps for
room-temperature persistent luminescence. This work calls for a re-assessment
of certain assumptions regarding specific carrier trapping centers made in all
mechanisms previously proposed for the persistent luminescence in Eu- and
(Eu,Dy)-doped SrAlO. It also serves as a methodological template for
the understanding and design of rare-earth doped phosphors.Comment: 15 pages, 14 figures, 4 table
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