TY - JOUR
T1 - Anisotropic Strain in Rare-Earth Substituted Ceria Thin Films Probed by Polarized Raman Spectroscopy and First-Principles Calculations
AU - Sediva, Eva
AU - Bohdanov, Dmytro
AU - Harrington, George F.
AU - Rafalovskyi, Iegor
AU - Drahokoupil, Jan
AU - Borodavka, Fedir
AU - Marton, Pavel
AU - Hlinka, Jiri
N1 - Funding Information:
The authors acknowledge the support of the Czech Academy of Sciences. This work was supported by the Czech Science Foundation (Project No. 19-28594X). G.F.H. acknowledges support from a Kakenhi Grant-in-Aid for Encouragement of Young Scientists (B) Award (Grant No. JP16K18235) and the Center of Innovation Science and Technology Based Radical Innovation and Entrepreneurship Program (COI Program), by the Japan Science and Technology Agency (JST) (Grant Number JPMJCE1318).
Publisher Copyright:
© 2020 American Chemical Society.
PY - 2020/12/16
Y1 - 2020/12/16
N2 - Lattice strain in oxygen ion conductors can be used to tune their functional properties for applications in fuel cells, sensors, or catalysis. However, experimental measurements of thin film strain in both in- and out-of-plane directions can be experimentally challenging. We propose a method for measuring strain in rare-earth doped ceria thin films by polarized Raman spectroscopy. We study epitaxial CeO2 films substituted by La, Gd, and Yb grown on MgO substrates with BaZrO3 and SrTiO3 interlayers, where different levels of strain are generated by annealing at distinct temperatures. The films show in-plane compression and out-of-plane expansion, resulting in a lowering from the bulk cubic to tetragonal lattice symmetry. This leads to the splitting of the F2g Raman mode in the cubic phase to B2g and Eg modes in the tetragonal lattice. The symmetry and frequency of these modes are determined by polarized Raman in the backscattering and right-angle scattering geometries as well as by first-principal calculations. The frequency splitting of the two modes is proportional to the strain measured by X-ray diffraction and its magnitude agrees with first-principles calculations. The results offer a fast, nondestructive, and precise method for measuring both in- and out-of-plane strain in ceria and can be readily applied to other ionic conductors.
AB - Lattice strain in oxygen ion conductors can be used to tune their functional properties for applications in fuel cells, sensors, or catalysis. However, experimental measurements of thin film strain in both in- and out-of-plane directions can be experimentally challenging. We propose a method for measuring strain in rare-earth doped ceria thin films by polarized Raman spectroscopy. We study epitaxial CeO2 films substituted by La, Gd, and Yb grown on MgO substrates with BaZrO3 and SrTiO3 interlayers, where different levels of strain are generated by annealing at distinct temperatures. The films show in-plane compression and out-of-plane expansion, resulting in a lowering from the bulk cubic to tetragonal lattice symmetry. This leads to the splitting of the F2g Raman mode in the cubic phase to B2g and Eg modes in the tetragonal lattice. The symmetry and frequency of these modes are determined by polarized Raman in the backscattering and right-angle scattering geometries as well as by first-principal calculations. The frequency splitting of the two modes is proportional to the strain measured by X-ray diffraction and its magnitude agrees with first-principles calculations. The results offer a fast, nondestructive, and precise method for measuring both in- and out-of-plane strain in ceria and can be readily applied to other ionic conductors.
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U2 - 10.1021/acsami.0c14249
DO - 10.1021/acsami.0c14249
M3 - Article
C2 - 33270441
AN - SCOPUS:85097784735
VL - 12
SP - 56251
EP - 56259
JO - ACS applied materials & interfaces
JF - ACS applied materials & interfaces
SN - 1944-8244
IS - 50
ER -