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Jingmin Zhang
Application of Electron Energy-Loss Spectroscopy to Ferroelectric Thin Films
Dissertation (2004),

High-resolution electron energy-loss spectroscopy (HR-EELS) and scanning transmission electron microscopy (STEM) have been applied to investigate BaTiO3/SrTiO3 ferroelectric multilayers and high- gate dielectric Y2O3/Si(001). The experiments are mainly concentrated on interface reactions and interface defects. The preparation of the STEM specimens and various experimental parameters which have strong effects on the acquisition of electron energy-loss spectra from the interface are discussed. In BaTiO3/SrTiO3 multilayers, oxygen vacancies have been found to preferably aggregate at the rough upper interface (SrTiO3/BaTiO3) while the lower interface (BaTiO3/SrTiO3) is nearly defect free. This finding has been explained in terms of misfit strain and oxygen vacancy ordering. The space charges formed by the aggregation of oxygen vacancies decrease the dielectric constant of ferroelectric multilayers. The crystal-field splitting of the Ti L23 edges is revealed to sensitively reflect the misfit strains. The lattice parameters of the BaTiO3 thin layer have been determined by selected-area electron diffraction, which confirm the presence of the strong misfit strains. In the high- gate dielectric Y2O3/Si(001), the interfacial SiOx (1
Keywords: BaTiO3, SrTiO3, Y2O3, Crystal-Field Splitting, Band-Structure, Full Multiple-Scattering Method , EELS

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