Phonon confinement and interface lattice dynamics of ultrathin high-k rare earth sesquioxide films: the case of Eu2O3 on YSZ(001)

Stankov, S.; Merkel, D. G.; Kalt, Jochen; Göttlicher, Jörg; Łażewski, J.; Sternik, M.; Jochym, Paweł T.; Piekarz, Przemysław; Baumbach, Tilo; Chumakov, A. I.; Rüffer, R.

doi:10.1039/d1na00728a

Cited by 2 publications

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“…These alterations of the vibrational dynamics can influence the coupling of phonons with particles and quasiparticles, e.g., electrons [38,43], magnons [44], and other phonons [45]. Another potential source of anomalies is the formation of an interlayer between the nanostructures and the substrate, which can significantly influence the overall vibrational properties [46].…”

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confidence: 99%

Lattice dynamics of β−FeSi2 nanorods

et al. 2022

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Here we present a combined experimental and ab initio lattice dynamics study of the semiconducting β phase of FeSi 2 . A polycrystalline β-FeSi 2 film was prepared on Si(111) and single-crystalline, self-assembled β-FeSi 2 nanorods were grown on Si(110) by molecular beam epitaxy. Both types of nanostructures were obtained by annealing of precursor structures, an epitaxial Fe film in the case of the film and high-aspect-ratio α-FeSi 2 nanowires in the case of the nanorods. The morphology and crystalline structure of the samples were investigated by reflection high-energy electron diffraction, atomic force microscopy, as well as x-ray diffraction and x-ray absorption spectroscopy. The Fe-partial phonon density of states (PDOS) was obtained from nuclear inelastic scattering. The PDOS of the film was investigated in the temperature range of 296 K down to 11 K and shows an excellent agreement with the ab initio calculations. In the PDOS of the nanorods, a shift in the number of states in the main features and an additional vibrational mode at 20 meV are observed. While the first effect can fully be explained by the specific orientation of the β-FeSi 2 unit cell on the Si(110) surface, the second effect is attributed to the formation of an α-FeSi 2 interlayer at the β-FeSi 2 /Si interface. Furthermore, the thermoelastic properties of the film show a harmonic behavior in the investigated temperature range. For the nanorods, no significant deviation from the film is observed, except for a small decrease of the sound velocity.

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Section: Introductionmentioning

confidence: 99%

Lattice dynamics of β−FeSi2 nanorods

et al. 2022

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Nuclear volume isotope fractionation of europium and other lanthanide elements

Schauble

2023

Geochem. J.

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The nuclear volume component of equilibrium field shift isotope fractionations in europium and other lanthanide elements is estimated using Mössbauer spectroscopy and electronic structure calculations. This effect goes in the opposite direction from equilibrium mass-dependent fractionation, and in the case of europium is predicted to dominate over mass dependent fractionation for most materials. Including both effects, Eu 2+ -bearing species will have approximately 0.4-1‰ higher 153 Eu/ 151 Eu than Eu 3+ -bearing species at 25ºC (298 K), and about 0.3‰ higher 153 Eu/ 151 Eu at 700ºC (973 K). Field shift fractionation mainly depends on oxidation state; differences in coordination structure without changes in oxidation state appear to have much weaker associated fractionations. Nuclear volume isotope fractionation will become even more dominant over mass dependent fractionation at higher temperatures because nuclear volume effects scale with 1/T (K), vs. 1/T 2 for mass-dependent fractionation.Fractionation favoring high 153 Eu/ 151 Eu in minerals that preferentially incorporate Eu 2+ , such as plagioclase, is consistent with recent measurements on igneous rocks showing low 153 Eu/ 151 Eu in samples with large negative europium anomalies (Lee and Tanaka, 2021). The present results agree with the recent conclusion that equilibrium fractionation cannot explain cosmochemical REE fractionations in primitive meteoritical materials (Hu et al., 2021), because the net fractionation is too small (~0.2‰ or less) at temperatures >1200 K where vapor-phase REE species are relevant.The field shift effect will also tend to drive 142 Ce/ xxx Ce ratios higher in reduced species (+2 > +3 > +4), for instance by 0.4‰ for 142 Ce/ 140 Ce in Ce 3+ vs. Ce 4+ at 25ºC, approximately canceling the mass-dependent fractionation. The nuclear volume component of fractionation in cerium isotope pairs not involving 142 Ce will be smaller (< 0.1‰) because the other nuclei have very similar volumes. As a result, mass-dependent fractionation will drive 138 Ce/ 140 Ce and 136 Ce/ 140 Ce lower in Ce 4+ species while 142 Ce/ 140 Ce hardly fractionates at equilibrium. This will yield an atypical mass vs. fractionation pattern in redox pairs.

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Phonon confinement and interface lattice dynamics of ultrathin high-k rare earth sesquioxide films: the case of Eu₂O₃ on YSZ(001)

Abstract: We demonstrate that sub-nanometer-thick layers exhibiting exotic crystal phases that might form at the interface between two materials constitute a source of novel vibrational dynamics of thin films and multilayers.

Cited by 2 publications

References 60 publications

Lattice dynamics of β−FeSi2 nanorods

Lattice dynamics of β−FeSi2 nanorods

Nuclear volume isotope fractionation of europium and other lanthanide elements

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