1,721,001 research outputs found
SURFACE AND MIXED-VALENCE EFFECTS IN XPS SPECTRA FROM YBCO
No full textWe report X-ray photoemission data from YBa2Cu3O7 showing that the measured composition and the electronic structure depend significantly upon the photo-electron escape depth. For large take-off angles the valence band spectrum near the Fermi edge is well structured and shows a number of features, arising from Cu---O hybrid states. Their intensities are drastically reduced in the energy distribution curves measured at grazing angles. The results are interpreted assuming that the surface is mainly composed by Ba---O planes. This interpretation is shown to be consistent with electronic structure calculations for the bulk and the Ba---O surface
Impurity effects and charge transport in ABO3 single crystal oxides: Photorefractivity-oriented and basic studies
No full textNon linear optical, dielectric, magnetic properties of ABO3 single crystal oxides let the implementation of acousto-optic, electro-optic, photonic, spintronic devices. In particular, significant role is played by the ferroelectric and photorefractive materials, where the photo-induced change in refractive indexes requires charge transport and impurities which support charge transfer, space charge formation and localization with accompanying electric field. Besides, ABO3 paraelectric perovskites regularly reveal newel effects connected with charge transport, e.g., photo-induced polar state recently reported for SrTiO3 and KTaO3. In this work we review our recent investigation, pointing out our studies of photo-transport in SrTiO3, Cu-doped KTaO3 and LiNbO3:Hf
Role of the Zhang-Rice-like exciton in optical absorption spectra of CuGeO3 and CuGe1-xSixO3 single crystals
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X-RAY-PHOTOEMISSION SPECTROSCOPY AND OPTICAL REFLECTIVITY OF YTTRIUM-STABILIZED ZIRCONIA
No full textX-ray-photoelectron spectroscopy (XPS) and optical measurements have been performed to investigate the structure of electronic states in yttrium-stabilized zirconia. From reflectivity observations, the spectral behavior of the dielectric function, of the energy loss, and of the effective electron number in the range 3-30 eV were obtained for single crystals with an yttria content of 12 and 24 mol%. This information, combined with binding-energy spectra from XPS, was used to infer the structure of valence and conduction states and to discuss the nature of the main optical transitions, also in connection with available theoretical data
AN XPS STUDY OF YTTRIA-STABILIZED ZIRCONIA SINGLE-CRYSTALS
No full textIt is shown that the shape and the binding energy positions of zirconium and yttrium core levels are independent of the yttria stoichiometry when the content of this oxide ranges from 12 to 24 mol.% of Y2O3
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