Details

Autor(en) / Beteiligte

• Ulreich, Manuel
• Boatner, Lynn A.
• Sokolović, Igor
• Reticcioli, Michele
• Stoeger, Berthold
• Poelzleitner, Flora
• Franchini, Cesare
• Schmid, Michael
• Diebold, Ulrike
• Setvin, Martin

Titel

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

Ist Teil von

• Physical review materials, 2019-07, Vol.3 (7)

Ort / Verlag

United States: American Physical Society (APS)

Erscheinungsjahr

2019

Quelle

American Physical Society Journals

Beschreibungen/Notizen

• Activator impurities and their distribution in the host lattice play a key role in scintillation phenomena. In this work 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 determined 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 moiré pattern. Crystals with poor optical transparency showed a significant degree of mosaicity and the presence of precipitates. All observed crystals contained a very low concentration of Eu dopants present as isolated point defects; most of the europium was incorporated in larger structures.