Characterization of tin oxides by x-ray-photoemission spectroscopy

Themlin, J.‐M.; Chtaïb, M.; Henrard, Luc; Lambin, Philippe; Darville, J.; Gilles, J.-M.

doi:10.1103/physrevb.46.2460

Cited by 344 publications

(262 citation statements)

References 10 publications

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“…The total EDOS shows that CsCl structured SnO has no band gap with a low density of states across the Fermi energy indicating that it is semi-metallic while litharge structured SnO has a small band gap of 0.6 eV. This is in line with x-ray photoelectron spectroscopy 19 which shows that on reduction of SnO 2 , which has a band gap of 3.6 eV, additional features that are attributed to the Sn 5s states appear close to the Fermi level, giving rise to a much smaller gap between the occupied and unoccupied states. Recent photoemission spectra 20 has also studied the valence states of SnO and again show a small band gap with a significant contribution of the Sn 5s to the states just below the Fermi level.…”

Section: Electronic Structure Of Snosupporting

confidence: 65%

“…It is this shift in energy that gives rise to the small band gap and corresponds to the Sn 5s character seen experimentally just below the top of the valence band. 19,20 The difference between the two EDOS is close to the Fermi surface where there is some Sn 5s character but the majority of it is involved in bonding interaction with O 2p between Ϫ9 and Ϫ6 eV. Partial electron density maps have been made for energy ranges of the EDOS.…”

Section: Electronic Structure Of Snomentioning

confidence: 99%

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The origin of the electron distribution in SnO

Watson

2001

The Journal of Chemical Physics

102

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Gradient corrected density functional theory calculations have been performed on SnO in the litharge and idealized CsCl structures with the litharge structure in good agreement with experiment. The CsCl structured SnO has a spherical electron density whereas the litharge structured SnO has a nonspherical electron distribution. Such asymmetry is often attributed to a sterically active lone pair formed by the 5s 2 electrons which does not take part in chemical bonding. However, analysis of the density of states and band structures indicates that the situation is more complicated. In CsCl structured SnO mixing of the Sn 5s with the oxygen 2p electronic states results in filled bonding and antibonding combinations. The antibonding combinations, at the top of valence band, can interact with Sn 5p to stabilize the structure, only when in the distorted litharge structure resulting in the asymmetric electron density. This is in contrast to the classical theory of hybridization of the tin 5s and 5p orbitals to form a ''lone pair'' as the asymmetric electron distribution is the result of the tin-oxygen covalent interactions.

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Section: Electronic Structure Of Snosupporting

confidence: 65%

Section: Electronic Structure Of Snomentioning

confidence: 99%

The origin of the electron distribution in SnO

Watson

2001

The Journal of Chemical Physics

102

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“…Although Ar + ion etching could change the film composition by preferentially ejecting O atoms, the effect would result in only 30∼40% of the Sn being converted. 14 Therefore, some SnO must have existed in the film prior to etching.…”

Section: Resultsmentioning

confidence: 99%

Characterization of the Mixed Oxide Layer Structure of the Ti/SnO₂-Sb₂O₅Anode by Photoelectron Spectroscopy and Impedance Spectroscopy

Kirk

Thorpe

2014

J. Electrochem. Soc.

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The in-depth chemistry of a Ti/SnO 2 -Sb 2 O 5 anode was investigated by X-ray photoelectron spectroscopy combined with ion etching. The coating was found to be composed of multiple layers of tin and titanium oxides and composition gradients at both the oxide-air and oxide-metal interfaces. The existence of such an extensive titanium oxide layer may be related to the fabrication of the Ti/SnO 2 -Sb 2 O 5 anode and subsequent inter-diffusion of species. Also, the surface tin oxide layer was found to be non-stoichiometric, which, in relation to the extensive titanium oxide structure, could be explained by a migration of oxygen toward the Ti substrate. Electrochemical tests showed that the film was unstable and continued to grow under anodic polarization. Impedance spectroscopy displayed a continuum in the dielectric relaxation time constants with depth. This variation in relaxation time constants was proposed to be caused by the continuous variation of the composition in the film. Anodes made of titanium-supported metal oxides are of industrial importance. Since the inception of the well-known Dimensionally Stable Anode (DSA), 1 many oxides, single or mixed, have been developed. These include RuO 2 , IrO 2 , PbO 2 and SnO 2 that are widely used in areas such as chlorine production, water electrolysis, ozone production, and electro-oxidation of organics in wastewater treatment. [1][2][3][4][5] For wastewater treatment, an electrode material having high efficiency and selectivity toward oxidation of organic compounds is desired.One candidate electrode material is the antimony doped tin oxide on Ti. This electrode is generally written as Ti/SnO 2 -Sb 2 O 5 . The coating material is composed of SnO 2 with a tetragonal structure.6 By doping the SnO 2 with Sb, the conductivity of the SnO 2 film can be greatly enhanced. Compared to other metal oxides, Ti/SnO 2 -Sb 2 O 5 is low in cost, low in toxicity but efficient in the oxidation of organic compounds. Therefore, this electrode material was considered a suitable candidate for wastewater treatment. However, this electrode also suffers the disadvantage of deactivation, and the issue of deactivation has been addressed by several authors.7-9 A primary reason for the deactivation of this anode is the formation of a passive layer underneath the coating. The passive layer was thought to be a TiO 2 layer that was formed from interaction with aqueous electrolytes. The deactivation was found to be particularly severe in the anodes with Ti/SnO 2 -Sb 2 O 5 .9 Since TiO 2 has very high resistivity (10 10 cm), a very high electric field develops under constant current operation. The high electric field then promotes the solid state drift of the ions in the layer. In an anode such as Ti/SnO 2 -Sb 2 O 5 , the oxide anions are driven inwards toward the Ti substrate and titanium ions are driven toward the solution side. Such drift would then result in further growth of the oxide layer.Titanium is known to form a passive layer almost instantly when exposed to air or an aerated electrolyte...

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“…However, as it is well-known, only the position of Sn 3d 5/2 peak is not sufficient to determine the presence of Sn 4+ or Sn 2+ species. [6] More information can be extracted from the stoichiometric ratio Sn/O ox. , ( [7] confirms the nonstoichiometry of the SnO x nanowires.…”

Section: Chemical Composition -Sno 2 Nanowiresmentioning

confidence: 99%

Nanowires of metal oxides for gas sensing applications

Kačiulis

Pandolfi

Comini

et al. 2008

Surface & Interface Analysis

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Nanowires of different metal oxides (SnO 2 , ZnO) have been grown by evaporation-condensation process. Their chemical composition has been investigated by using XPS. The standard XPS quantification through main photoelectron peaks, modified Auger parameter and valence band spectra were examined for the accurate determination of oxidation state of metals in the nanowires.Morphological investigation has been conducted by acquiring and analyzing the SEM images. For the simulation of working conditions of sensor, the samples were annealed in ultra high vacuum (UHV) up to 500 • C and XPS analysis repeated after this treatment. Finally, the nanowires of SnO 2 have were used to produce a novel gas sensor based on Pt/oxide/SiC structure and operating as Schottky diode.

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Characterization of tin oxides by x-ray-photoemission spectroscopy

Cited by 344 publications

References 10 publications

The origin of the electron distribution in SnO

The origin of the electron distribution in SnO

Characterization of the Mixed Oxide Layer Structure of the Ti/SnO₂-Sb₂O₅Anode by Photoelectron Spectroscopy and Impedance Spectroscopy

Nanowires of metal oxides for gas sensing applications

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Characterization of tin oxides by x-ray-photoemission spectroscopy

Cited by 344 publications

References 10 publications

The origin of the electron distribution in SnO

The origin of the electron distribution in SnO

Characterization of the Mixed Oxide Layer Structure of the Ti/SnO2-Sb2O5Anode by Photoelectron Spectroscopy and Impedance Spectroscopy

Nanowires of metal oxides for gas sensing applications

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Characterization of the Mixed Oxide Layer Structure of the Ti/SnO₂-Sb₂O₅Anode by Photoelectron Spectroscopy and Impedance Spectroscopy