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Suitability of Raman Spectroscopy for Assessing Anisotropic Strain in Thin Films of Doped Ceria
摘要： 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 F2g 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 F2g 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.
关键词： doped ceria,Raman spectroscopy,Grüneisen parameter,anelastic relaxation
更新于2025-09-23 15:23:52
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Equi-biaxial compressive strain in graphene: Grüneisen parameter and buckling ridges
摘要： Here we report equi-biaxial compressive strain in monolayer graphene on SiO2 and Si3N4 substrates induced by thermal cycling in vacuum. The equi-biaxial strain is attributed to the mismatch in coefficient of thermal expansion between graphene and the substrate and sliding of graphene on the substrate. Importantly, the induced buckling ridges in graphene exhibit a pattern representing the symmetry of graphene crystal structure, which agreed well with our molecular dynamics (MD) simulations. Furthermore, these thermally-induced buckling ridges were found reminiscent of those in graphene synthesized by the CVD and SiC sublimation methods, suggesting the same origin of formation of the buckling ridges.
关键词： biaxial strain,thermal cycling,graphene,buckling ridges,molecular dynamics simulation,Grüneisen parameter
更新于2025-09-09 09:28:46