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Suitability of Raman Spectroscopy for Assessing Anisotropic Strain in Thin Films of Doped Ceria
Author(s) -
Kraynis Olga,
Makagon Evgeniy,
Mishuk Eran,
Hartstein Michal,
Wachtel Ellen,
Lubomirsky Igor,
Livneh Tsachi
Publication year - 2019
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201804433
Subject(s) - materials science , raman spectroscopy , thin film , substrate (aquarium) , doping , anisotropy , analytical chemistry (journal) , strain (injury) , relaxation (psychology) , nanotechnology , optics , optoelectronics , organic chemistry , chemistry , medicine , psychology , social psychology , oceanography , physics , geology
A protocol for characterizing relaxation of anisotropic strain in thin films of 10 mol% Eu‐ or Sm‐doped ceria is described. The method is based on comparison of Raman spectra and X‐ray diffraction patterns from substrate‐supported films, displaying in‐plane compressive strain (initial state), with analogous data from 2 mm diameter self‐supported films (i.e., membranes), prepared by partial substrate removal (final state). These membranes are found to be relaxed, i.e., approximately unstrained, but with increased unit cell volume. The effective (i.e., 2‐state) Grüneisen parameter of the F 2g Raman active mode for these films is calculated to be 0.4 ± 0.1, which is ≈30% of the literature value for the corresponding ceramics under isostatic pressure. On this basis, it is found that the observed red‐shift of the F 2g mode frequency following isothermal strain relaxation of the doped ceria thin films cannot be determined solely by the increase in average unit cell volume. The study presented here may shed light on the suitability of Raman spectroscopy as a technique for characterizing strain in lanthanide‐doped ceria thin films.