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dc.contributor.authorChen, Boen_US
dc.date.accessioned2016-03-31T15:05:01Z
dc.date.available2016-03-31T15:05:01Z
dc.date.issued2014
dc.identifier.urihttps://hdl.handle.net/2144/15385
dc.description.abstractTransition-metal oxides (TMOs) display numerous fascinating and complex properties, such as mixed-valency, low dimensionality, lattice distortion, and phase transition, etc. These properties arise from the partially filled d- or f-electron shells of TM cations and are often accompanied by the intriguing interplay between degrees of freedom. To understand the complexity of d-electron TMOs, this thesis is primarily focused on studying their underlying electronic structure using X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), X-ray photoemission spectroscopy (XPS), and resonant inelastic X-ray scattering (RIXS). The measurements at the O K- and TM L-edges are achieved by taking advantage of high-flux and high-resolution synchrotron radiation light with tunable monochromatic photon energy. Four electronically and structurally distinctive oxides are selected as representative TMOs for investigation in this thesis. To begin with, through a comparative study of WO3 and Na0.67WO3 crystals, the narrowing of the conduction band is observed with Na doping and the core-hole energy shift in the O K-edge XAS process is experimentally determined. Indirect and direct band gaps of photoanode WO3 are measured from the resonant XES with polarization-dependent experimental geometry. The other sodium bronze studied is quasi-one-dimensional β-Na0.33V2O5 polycrystalline film. The film stoichiometry, preferential orientation, and orbital anisotropy are well characterized by a variety of photon and electron techniques and compared to density-functional theory (DFT) calculation. The V 3d orbital splitting of β-Na0.33V2O5 is surveyed by the V L-edge RIXS and compared with isoelectronic β-Sr0.17V2O5 regarding distortions to VO6 octahedra. Furthermore, the complex electronic structure of Mott insulators La1-xLuxVO3 is investigated to understand their spin-orbital phase diagram. The effects of rare-earth size on the O 2p hybridization states and the local crystal field of VO6 octahedron are found to agree with the prediction of DFT calculation and the evolution of crystal structure. The changes of experimental spectra with temperature are associated with Jahn-Teller distortion and orbital ordering due to structural phase transition. Lastly, the band structure and low-energy excitations of spinel MnV2O4 are explored using soft x-ray spectroscopies and theoretical calculations. The presence of Hubbard bands and the mixing between V and Mn 3d states are suggested both experimentally and theoretically.en_US
dc.language.isoen_US
dc.subjectPhysicsen_US
dc.subjectDensity functional theoryen_US
dc.subjectElectronic structureen_US
dc.subjectTransition-metal oxidesen_US
dc.subjectX-ray absorption spectroscopyen_US
dc.subjectX-ray emission spectroscopyen_US
dc.subjectX-ray photoemission spectroscopyen_US
dc.titleStudy of the electronic structure of transition-metal oxides by synchrotron-based X-ray spectroscopiesen_US
dc.typeThesis/Dissertationen_US
dc.date.updated2016-03-12T07:12:32Z
etd.degree.nameDoctor of Philosophyen_US
etd.degree.leveldoctoralen_US
etd.degree.disciplinePhysicsen_US
etd.degree.grantorBoston Universityen_US


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