研究目的
To examine whether Raman spectroscopy can successfully assess strain in thin films of doped ceria, with implications for other materials containing a large concentration of oxygen vacancies.
研究成果
The effective isothermal Grüneisen parameter for doped ceria films is 0.4 ± 0.1, about 30% of literature values under hydrostatic pressure, attributed to anelastic mechanical properties and anharmonic effects. Raman spectroscopy requires consideration of anharmonic effects, elastic moduli, thermal history, and defect concentration for reliable strain characterization in such films.
研究不足
The methodology compares only two states (compressed and relaxed) rather than continuous changes, and the effective Grüneisen parameter has a relatively large uncertainty (±0.1) that may mask dopant or anisotropy differences. The absence of complete anisotropy assurance in membranes and reliance on assumptions for in-plane lattice parameter calculation are limitations.
1：Experimental Design and Method Selection:
The study uses a protocol comparing Raman spectra and X-ray diffraction patterns from substrate-supported films (initial state with in-plane compressive strain) and self-supported membranes (final relaxed state) to characterize strain relaxation. The effective Grüneisen parameter is calculated based on volume changes and Raman frequency shifts.
2：Sample Selection and Data Sources:
Thin films of 10 mol% Eu- or Sm-doped ceria (Ce0.9Do0.1O1.95) were deposited by RF-magnetron sputtering onto Al-coated silicon wafers. Samples included as-deposited and annealed films to vary initial strain.
3：9Do1O95) were deposited by RF-magnetron sputtering onto Al-coated silicon wafers. Samples included as-deposited and annealed films to vary initial strain.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: RF-magnetron sputtering system (AJA brand), X-ray diffractometer (Rigaku TTRAX), Raman spectrometer (Horiba LabRAM HR Evolution), optical profiler (Zeta-20), photolithography setup for membrane fabrication, and materials including CeO2, Eu2O3, Sm2O3 targets (Able Target Limited), Al, and Si wafers.
4：Experimental Procedures and Operational Workflow:
Films were deposited, characterized by XRD for lattice parameters, converted to membranes by partial substrate removal, and analyzed using Raman spectroscopy and profilometry to measure volume changes and frequency shifts.
5：Data Analysis Methods:
XRD data analyzed using Williamson-Hall method for crystallite size, Raman peak positions fitted with Lorentzian profiles, and surface area changes calculated from profilometry data to determine lattice parameters and Grüneisen parameters.
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