Electronic properties of reduced molybdenum oxides

K. Inzani, M. Nematollahi, F. Vullum-Bruer, T. Grande, T. W. Reenaas, S. M. Selbach

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    Abstract

    The electronic properties of MoO3 and reduced molybdenum oxide phases are studied by density functional theory (DFT) alongside characterization of mixed phase MoOx films. Molybdenum oxide is utilized in compositions ranging from MoO3 to MoO2 with several intermediary phases. With increasing degree of reduction, the lattice collapses and the layered MoO3 structure is lost. This affects the electronic and optical properties, which range from the wide band gap semiconductor MoO3 to metallic MoO2. DFT is used to determine the stability of the most relevant molybdenum oxide phases, in comparison to oxygen vacancies in the layered MoO3 lattice. The non-layered phases are more stable than the layered MoO3 structure for all oxygen stoichiometries of MoOx studied where 2 $ x textless 3. Reduction and lattice collapse leads to strong changes in the electronic density of states, especially the filling of the Mo 4d states. The DFT predictions are compared to experimental studies of molybdenum oxide films within the same range of oxygen stoichiometries. We find that whilst MoO2 is easily distinguished from MoO3, intermediate phases and phase mixtures have similar electronic structures. The effect of the different band structures is seen in the electrical conductivity and optical transmittance of the films. Insight into the oxide phase stability ranges and mixtures is not only important for understanding molybdenum oxide films for optoelectronic applications, but is also relevant to other transition metal oxides, such as WO3, which exist in analogous forms.
    Original languageEnglish
    Pages (from-to)9232-9245
    Number of pages14
    JournalPhysical chemistry chemical physics
    Volume19
    Issue number13
    DOIs
    Publication statusPublished - 2017

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    Molybdenum oxide
    molybdenum oxides
    Electronic properties
    electronics
    density functional theory
    Density functional theory
    oxide films
    stoichiometry
    oxygen
    Stoichiometry
    Oxides
    Oxide films
    Oxygen
    metal oxides
    Electronic density of states
    Phase stability
    transmittance
    Opacity
    Oxygen vacancies
    transition metals

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    Inzani, K., Nematollahi, M., Vullum-Bruer, F., Grande, T., Reenaas, T. W., & Selbach, S. M. (2017). Electronic properties of reduced molybdenum oxides. Physical chemistry chemical physics, 19(13), 9232-9245. https://doi.org/10.1039/c7cp00644f
    Inzani, K. ; Nematollahi, M. ; Vullum-Bruer, F. ; Grande, T. ; Reenaas, T. W. ; Selbach, S. M. / Electronic properties of reduced molybdenum oxides. In: Physical chemistry chemical physics. 2017 ; Vol. 19, No. 13. pp. 9232-9245.
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    abstract = "The electronic properties of MoO3 and reduced molybdenum oxide phases are studied by density functional theory (DFT) alongside characterization of mixed phase MoOx films. Molybdenum oxide is utilized in compositions ranging from MoO3 to MoO2 with several intermediary phases. With increasing degree of reduction, the lattice collapses and the layered MoO3 structure is lost. This affects the electronic and optical properties, which range from the wide band gap semiconductor MoO3 to metallic MoO2. DFT is used to determine the stability of the most relevant molybdenum oxide phases, in comparison to oxygen vacancies in the layered MoO3 lattice. The non-layered phases are more stable than the layered MoO3 structure for all oxygen stoichiometries of MoOx studied where 2 $ x textless 3. Reduction and lattice collapse leads to strong changes in the electronic density of states, especially the filling of the Mo 4d states. The DFT predictions are compared to experimental studies of molybdenum oxide films within the same range of oxygen stoichiometries. We find that whilst MoO2 is easily distinguished from MoO3, intermediate phases and phase mixtures have similar electronic structures. The effect of the different band structures is seen in the electrical conductivity and optical transmittance of the films. Insight into the oxide phase stability ranges and mixtures is not only important for understanding molybdenum oxide films for optoelectronic applications, but is also relevant to other transition metal oxides, such as WO3, which exist in analogous forms.",
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    Inzani, K, Nematollahi, M, Vullum-Bruer, F, Grande, T, Reenaas, TW & Selbach, SM 2017, 'Electronic properties of reduced molybdenum oxides' Physical chemistry chemical physics, vol. 19, no. 13, pp. 9232-9245. https://doi.org/10.1039/c7cp00644f

    Electronic properties of reduced molybdenum oxides. / Inzani, K.; Nematollahi, M.; Vullum-Bruer, F.; Grande, T.; Reenaas, T. W.; Selbach, S. M.

    In: Physical chemistry chemical physics, Vol. 19, No. 13, 2017, p. 9232-9245.

    Research output: Contribution to journalArticleAcademicpeer-review

    TY - JOUR

    T1 - Electronic properties of reduced molybdenum oxides

    AU - Inzani, K.

    AU - Nematollahi, M.

    AU - Vullum-Bruer, F.

    AU - Grande, T.

    AU - Reenaas, T. W.

    AU - Selbach, S. M.

    PY - 2017

    Y1 - 2017

    N2 - The electronic properties of MoO3 and reduced molybdenum oxide phases are studied by density functional theory (DFT) alongside characterization of mixed phase MoOx films. Molybdenum oxide is utilized in compositions ranging from MoO3 to MoO2 with several intermediary phases. With increasing degree of reduction, the lattice collapses and the layered MoO3 structure is lost. This affects the electronic and optical properties, which range from the wide band gap semiconductor MoO3 to metallic MoO2. DFT is used to determine the stability of the most relevant molybdenum oxide phases, in comparison to oxygen vacancies in the layered MoO3 lattice. The non-layered phases are more stable than the layered MoO3 structure for all oxygen stoichiometries of MoOx studied where 2 $ x textless 3. Reduction and lattice collapse leads to strong changes in the electronic density of states, especially the filling of the Mo 4d states. The DFT predictions are compared to experimental studies of molybdenum oxide films within the same range of oxygen stoichiometries. We find that whilst MoO2 is easily distinguished from MoO3, intermediate phases and phase mixtures have similar electronic structures. The effect of the different band structures is seen in the electrical conductivity and optical transmittance of the films. Insight into the oxide phase stability ranges and mixtures is not only important for understanding molybdenum oxide films for optoelectronic applications, but is also relevant to other transition metal oxides, such as WO3, which exist in analogous forms.

    AB - The electronic properties of MoO3 and reduced molybdenum oxide phases are studied by density functional theory (DFT) alongside characterization of mixed phase MoOx films. Molybdenum oxide is utilized in compositions ranging from MoO3 to MoO2 with several intermediary phases. With increasing degree of reduction, the lattice collapses and the layered MoO3 structure is lost. This affects the electronic and optical properties, which range from the wide band gap semiconductor MoO3 to metallic MoO2. DFT is used to determine the stability of the most relevant molybdenum oxide phases, in comparison to oxygen vacancies in the layered MoO3 lattice. The non-layered phases are more stable than the layered MoO3 structure for all oxygen stoichiometries of MoOx studied where 2 $ x textless 3. Reduction and lattice collapse leads to strong changes in the electronic density of states, especially the filling of the Mo 4d states. The DFT predictions are compared to experimental studies of molybdenum oxide films within the same range of oxygen stoichiometries. We find that whilst MoO2 is easily distinguished from MoO3, intermediate phases and phase mixtures have similar electronic structures. The effect of the different band structures is seen in the electrical conductivity and optical transmittance of the films. Insight into the oxide phase stability ranges and mixtures is not only important for understanding molybdenum oxide films for optoelectronic applications, but is also relevant to other transition metal oxides, such as WO3, which exist in analogous forms.

    U2 - 10.1039/c7cp00644f

    DO - 10.1039/c7cp00644f

    M3 - Article

    VL - 19

    SP - 9232

    EP - 9245

    JO - Physical chemistry chemical physics

    JF - Physical chemistry chemical physics

    SN - 1463-9076

    IS - 13

    ER -