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Phonon density of states in lanthanide-based nanocrystals

Li, Z. H.; Hudry, D.; Heid, R.; Said, A. H.; Le, M. D.; Popescu, R.; Gerthsen, D.; Merz, M.; Krämer, K. W.; Busko, D.; Howard, I. A.; Richards, B. S.; Weber, F.

Abstract (englisch):
We report a combined inelastic neutron- and x-ray-scattering study of the phonon density of states of the
nano- and microcrystalline lanthanide-based materials NaY0.8Yb0.18Er0.02F4 and NaGd0.8Yb0.18Er0.02F4. While
large (20 nm) nanocrystals display the same vibrational spectra as their microcrystalline counterparts, we find
an enhanced phonon density of states at low energies, E 15 meV, in ultrasmall (5 nm) NaGd0.8Yb0.18Er0.02F4
nanocrystals which we assign to an increased relative spectral weight of surface phonon modes. Based on our
observations for ultrasmall nanocrystals, we rationalize that an increase of the phonon density of states in large
nanocrystals due to surface phonons is too small to be observed in the current measurements. The experimental
approach described in this paper constitutes a step toward the rationalization of size effects on the modification
of the absolute upconversion quantum yield of upconverting nanocrystals.

DOI: 10.1103/PhysRevB.102.165409
Zugehörige Institution(en) am KIT Institut für Quantenmaterialien und -technologien (IQMT)
Publikationstyp Zeitschriftenaufsatz
Publikationsdatum 19.10.2020
Sprache Englisch
Identifikator ISSN: 2469-9950, 2469-9969
KITopen-ID: 1000124852
HGF-Programm 43.21.01 (POF III, LK 01)
Quantum Correlations in Condensed Matter
Erschienen in Physical review / B
Band 102
Heft 16
Seiten Article no: 165409
Vorab online veröffentlicht am 23.09.2020
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