Browsing by Subject "Valence band edges"

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    Preparation, surface state and band structure studies of SrTi (1-X)Fe (x)O (3-δ) (x = 0-1) perovskite-type nano structure by X-ray and ultraviolet photoelectron spectroscopy
    (2012) Ghaffari, M.; Shannon, M.; Hui H.; Tan O.K.; Irannejad, A.
    In this report, SrTi (1 - x)Fe (x)O (3 - δ) photocatalyst powder was synthesized by a high temperature solid state reaction method. The morphology, crystalline structures of obtained samples, was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM), respectively. The electronic properties and local structure of the perovskite STF x (0 ≤ x ≤ 1) systems have been probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. The effects of iron doping level x (x = 0-1) on the crystal structure and chemical state of the STF x have been investigated by X-ray photoelectron spectroscopy and the valence band edges for electronic band gaps were obtained for STF x by ultraviolet photoelectron spectroscopy (UPS). A single cubic perovskite phase of STF x oxide was successfully obtained at 1200 °C for 24 h by the solid state reaction method. The XPS results showed that the iron present in the STF x perovskite structure is composed of a mixture of Fe 3+ and Fe 4+ (SrTi (1 - x)[Fe 3+, Fe 4+] (x)O (3 - δ)). When the content x of iron doping was increased, the amount of Fe 3+ and Fe 4+ increased significantly and the oxygen lattice decreased on the surface of STF x oxide. The UPS data has confirmed that with more substitution of iron, the position of the valence band decreased. © 2011 Elsevier B.V. All rights reserved.