Surface composition of MnxCo1−xO solid solutions by X-ray photoelectron and Auger spectroscopies

Langell, M. A.; Gevrey, Frédéric; Nydegger, Michael W.

doi:10.1016/s0169-4332(99)00361-x

Cited by 25 publications

(17 citation statements)

References 31 publications

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“…The observed significant differences between the bulk and surface composition could not be explained without an additional extensive study, and will be reported elsewhere. Such differences were already shown for films formed from mixtures of pure metal oxides [44,45]. This was explained by surface segregation effects.…”

Section: Raman Shift [Cm -1 ]supporting

confidence: 51%

Plasma Deposition and Characterization of Copper-doped Cobalt Oxide Nanocatalysts

Tyczkowski

Kapica

Redzynia

et al. 2013

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A series of pure and copper-doped cobalt oxide films was prepared by plasma-enhanced metalorganic chemical vapor deposition (PEMOCVD). The effect of Cu-doping on the chemical structure and morphology of the deposited films was investigated. Raman and FTIR spectroscopies were used to characterize the chemical structure and morphology of the produced films. The bulk composition and homogeneity of the samples were investigated by energy dispersive X-ray microanalysis (EDX), and X-ray photoelectron spectroscopy (XPS) was employed to assess the surface chemical composition of pure and doped materials. The obtained results permit to affirm that the PEMOCVD technique is a simple, versatile and efficient method for providing homogeneous layers of cobalt oxides with a different content of copper. It has been found that pure cobalt oxide films mainly contain Co 3 O 4 in the form of nanoclusters whereas the films doped with Cu are much more complex, and CoO x (also Co 3 O 4), mixed Co-Cu oxides and CuO x nanoclusters are detected in them. Preliminary catalytical tests show that Cu-doped cobalt oxide films allow to initiate catalytic combustion of n-hexane at a lower temperature compared to the pure cobalt oxide (Co 3 O 4) films. From what has been stated above, the plasma-deposited thin films of Cu-doped cobalt oxides pave the way towards a new class of nanomaterials with interesting catalytic properties.

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Section: Raman Shift [Cm -1 ]supporting

confidence: 51%

Plasma Deposition and Characterization of Copper-doped Cobalt Oxide Nanocatalysts

Tyczkowski

Kapica

Redzynia

et al. 2013

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“…In addition to hydroxyl contamination resulting even from low pressure H 2 O background contaminants from the UHV chamber, the peak has been proposed to result from non-stoichiometric near-surface oxygen [24,46], cation defects in spinel-like near-surface layers [21,44], phases resulting from surface segregation of one bulk metal component along with increased oxidation of the near-surface region [29], a fi nal-state effect intrinsic to the spinel surface [47] and even a residual substrate signal from the oxide upon which the spinel was grown [29]. The very intense nature indicates that the peak is characteristic of a species that is more than simply a casual contaminant that formed on the outermost layer from UHV ambient absorption.…”

Section: Discussionmentioning

confidence: 99%

Analysis of the NiCo2O4 spinel surface with Auger and X-ray photoelectron spectroscopy

Kim

Pugmire

Battaglia

et al. 2000

Applied Surface Science

493

238

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“…represent mixing coefficients for the ground state with the Co 2ϩ 3d 7 cation in the valence band structure. This satellite feature is suppressed by the formation of low spin Co 3ϩ 3d 6 and it is clear that unpaired electrons or occupied e g states are required to allow detectible amounts of both mechanisms.…”

Section: Discussionmentioning

confidence: 99%

“…Substitutional and interstitial defects are also common in these materials 5 and surface compositions can differ from that of the bulk due to either thermodynamic or kinetic factors. 4,6 Water is one oxidant commonly encountered under ambient conditions, and most air-exposed TMOs are covered with one or more hydroxylated layers. 7 While hydroxylation occurs rapidly under ultrahigh vacuum ͑UHV͒ only at isolated defect sites, 8,9 air-exposed TMO substrates can form relatively thick hydroxylated layers that persist in UHV to temperatures of 973 K or higher for substantial periods of time.…”

Section: Introductionmentioning

confidence: 99%

Nature of oxygen at rocksalt and spinel oxide surfaces

Langell

Kim

Pugmire

et al. 2001

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The chemical environment of oxygen in cobalt-containing metal oxides with compositions͑M,MЈϭMn,Ni,Co͒ has been studied by Auger, x-ray and ultraviolet photoelectron, and high resolution electron energy loss spectroscopies. While there is a single type of lattice oxygen in the bulk structure of simple rocksalt and spinel oxides, the nature of oxygen at the surface of the spinel oxides is considerably more complex. Photoemission from core oxygen states in these materials often shows multiple peaks and satellite structure which have been attributed to a range of intrinsic and extrinsic oxygen states. All of these 3d transition metal oxides show a single, intense O 1s core photoemission peak at approximately 529.6 eV. In the spinel materials, a second state at 531.2 eV is also observed and is shown to be intrinsic to the spinel surface and not a result of hydroxylation or other surface contaminant. Similar photoemission features in Fe 3 O 4 were previously attributed to final state effects; however, the nature of the multiple final states remains to be elucidated.

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Surface composition of MnxCo1−xO solid solutions by X-ray photoelectron and Auger spectroscopies

Cited by 25 publications

References 31 publications

Plasma Deposition and Characterization of Copper-doped Cobalt Oxide Nanocatalysts

Plasma Deposition and Characterization of Copper-doped Cobalt Oxide Nanocatalysts

Analysis of the NiCo2O4 spinel surface with Auger and X-ray photoelectron spectroscopy

Nature of oxygen at rocksalt and spinel oxide surfaces

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