XAS and GIXRD Study of Co Sites in CoAl2O4 Layers Grown by MOCVD (Articolo in rivista)

Type
Label
  • XAS and GIXRD Study of Co Sites in CoAl2O4 Layers Grown by MOCVD (Articolo in rivista) (literal)
Anno
  • 2010-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1021/cm9018106 (literal)
Alternative label
  • iChiara Maurizio; Naida El Habra; Gilberto Rossetto; Marco Merlini; Elti Cattaruzza; Luciano Pandolfo; Maurizio Casarin (2010)
    XAS and GIXRD Study of Co Sites in CoAl2O4 Layers Grown by MOCVD
    in Chemistry of materials
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • iChiara Maurizio; Naida El Habra; Gilberto Rossetto; Marco Merlini; Elti Cattaruzza; Luciano Pandolfo; Maurizio Casarin (literal)
Pagina inizio
  • 1933 (literal)
Pagina fine
  • 1942 (literal)
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  • http://pubs.acs.org/doi/pdf/10.1021/cm9018106 (literal)
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  • 22 (literal)
Rivista
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  • 10 (literal)
Note
  • ISI Web of Science (WOS) (literal)
  • Scopu (literal)
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  • INFM-CNR, OGG-European Synchrotron Radiation Facility, GILDA-CRG B.P. 220, F-38043 Grenoble France / Istituto di Chimica Inorganica e delle Superfici del CNR, Padova, Italy / Dipartimento di Scienze Chimiche, Universit degli Studi di Padova, Padova, Italy / European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble, France / Dipartimento di Chimica Fisica, Universit Ca’ Foscari, Venezia, Italy / Consorzio Interuniversitario di Scienza e Tecnologia dei Materiali, Firenze 50121, Italy / Consorzio Interuniversitario di Scienza e Tecnologia dei Materiali, Firenze 50121, Italy (literal)
Titolo
  • XAS and GIXRD Study of Co Sites in CoAl2O4 Layers Grown by MOCVD (literal)
Abstract
  • The chemical environment of Co sites in CoAl2O4 layers grown by metal-organic chemical vapor deposition has been investigated by X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD). It is shown that the air- or [O2 þ H2O]-annealing at 500 ?C of the layers deposited at low temperature induce a partial crystallization with the formation of (Co1-2?Al2?)(Co2?Al2(1-?))O4 spinel (?=0.2-0.27). Nevertheless, slightly more than half of Co remains in an amorphous phase, and XAS data are consistent with the formation of a medium-range ordered Co3O4 phase, especially upon air-annealing. Layers grown at higher temperatures (600-650 ?C) exhibit a similar but more complex structure, since the presence of an additional medium-range ordered phase (likely, CoAl2O4) is also revealed. The air-annealing at high temperature (800 ?C) generates blue, almost completely crystalline, CoAl2O4 layers. Optical properties of deposited layers are discussed by referring to the outcomes of structural results. In particular, the optical absorption spectrum results negligibly affected by the presence of the amorphous phase, while absorptions present in the 300-500 nmrange, responsible for the green layer color and evident in samples annealed in an oxidizing atmosphere or grown at high temperature, are likely caused by the octahedrally coordinated Co ions of the partially inverted spinel (Co1-2?Al2?)(Co2?Al2(1-?))O4 phase. Despite the XRD analysis that ultimately demonstrates the presence of octahedrally coordinated Co ions, whose oxidation state in the spinel phase is in majority Co(II), the occurrence of Co(III) species with an octahedral environment cannot be ruled out. (literal)
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