Defect chemistry of Eu dopants in NaI scintillators studied by atomically resolved force microscopy

Author(s)
Manuel Ulreich, Lynn A. Boatner, Igor Sokolovic, Michele Reticcioli, Berthold Stoeger, Flora Poelzleitner, Cesare Franchini, Michael Schmid, Ulrike Diebold, Martin Setvin
Abstract

Activator impurities and their distribution in the host lattice play a key role in scintillation phenomena. Here a combination of cross-sectional noncontact atomic force microscopy, x-ray photoelectron spectroscopy, and density-functional theory were used to study the distribution of Eu2+ dopants in a NaI scintillator activated by 3% EuI2. A variety of Eu-based structures were identified in crystals subjected to different postgrowth treatments. Transparent crystals with good scintillation properties contained mainly small precipitates with a cubic crystal structure and a size below 4 nm. Upon annealing, Eu segregated toward the surface, resulting in the formation of an ordered hexagonal overlayer with a EuI2 composition and a pronounced, unidirectional moire pattern. Crystals with poor optical transparency showed a significant degree of mosaicity and the presence of precipitates. All investigated crystals contained a very low concentration of Eu dopants present as isolated point defects; most of the europium was incorporated in larger structures.

Organisation(s)
Computational Materials Physics
External organisation(s)
Technische Universität Wien, Oak Ridge National Laboratory , Università degli Studi di Bologna
Journal
Physical Review Materials
Volume
3
No. of pages
7
ISSN
2475-9953
DOI
https://doi.org/10.1103/PhysRevMaterials.3.075004
Publication date
07-2019
Peer reviewed
Yes
Austrian Fields of Science 2012
Materials physics
Keywords
Portal url
https://ucris.univie.ac.at/portal/en/publications/defect-chemistry-of-eu-dopants-in-nai-scintillators-studied-by-atomically-resolved-force-microscopy(a2161a24-77ed-4bfd-a6da-9e2a04d28ae4).html