Optical Absorption in Cerium Dioxide Thin Films

Sundaram, Kalpathy B.; Wahid, Parveen

doi:10.1002/pssb.2221610158

Cited by 54 publications

(17 citation statements)

References 4 publications

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“…The band gap observed for the gold samples are different each other, thus pointing to the existence of differences in the electronic and acid/base properties among them. It has been proposed that the energy of the band gap carry information about the average crystalline domain size of the oxide (CeO 2 in our case) particles, in such a way that the domain size increase when the band gap energy decreases [16,17], however as the measured band gap for the supported ceria particles is quite close to that measured for the bulk oxide, 3.1 eV [16,25], it should be considered that all the observed modifications are due to the presence of gold levels being independent of the domain size of ceria particles.…”

Section: Resultssupporting

confidence: 63%

Gold supported CeO2/Al2O3 catalysts for CO oxidation: influence of the ceria phase

et al. 2005

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A series of low loading gold supported ceria/alumina catalysts have been prepared by the deposition-precipitation method, varying the pH of the synthesis. The catalysts were characterised by means of XRD, TEM, S BET , XRF and UV-Vis techniques, and their catalytic activity towards CO oxidation in the absence and in presence of water in the stream, were tested. It has been found that in this low loading gold catalysts, where the metallic particles are far away one from another and the oxygen transportation is not the limiting step of the reaction, the electronic properties of the ceria phase and the structure of the metal-support perimeter more than the diameter of the gold nanoparticles is the determinant factor in the catalytic performances of the solid.

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Section: Resultssupporting

confidence: 63%

Gold supported CeO2/Al2O3 catalysts for CO oxidation: influence of the ceria phase

et al. 2005

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“…Ceria is n-type semiconductor with band gap energy (E g ) equal to 2.94 eV and consequently it can be activated by irradiation with light in the near UV-Vis range [66]. DRS has been used extensively to study ceria-based materials and transition metal oxides to obtain information on surface co-ordination and different oxidation states of the metal ions by measuring d-d, f-d transitions and oxygen-metal ion charge transfer bands.…”

Section: Uv-vis Drs Measurementsmentioning

confidence: 99%

Nanosized CeO2–SiO2, CeO2–TiO2, and CeO2–ZrO2 Mixed Oxides: Influence of Supporting Oxide on Thermal Stability and Oxygen Storage Properties of Ceria

2005

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The influence of SiO 2 , TiO 2 , and ZrO 2 on the structural and redox properties of CeO 2 were systematically investigated by various techniques namely, X-ray diffraction (XRD), Raman spectroscopy (RS), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HREM), BET surface area, and thermogravimetry methods. The effect of supporting oxides on the crystal modification of ceria was also mainly focused. The investigated oxides were obtained by soft chemical routes with ultrahigh dilute solutions and were subjected to thermal treatments from 773 to 1073 K. The XRD results suggest that the CeO 2 -SiO 2 sample primarily consists of nanocrystalline CeO 2 on the amorphous SiO 2 surface. Both crystalline CeO 2 and TiO 2 -anatase phases were noted in the case of CeO 2 -TiO 2 sample. Formation of cubic Ce 0.75 Zr 0.25 O 2 and Ce 0.6 Zr 0.4 O 2 (at 1073 K) were observed in the case of CeO 2 -ZrO 2 sample. The cell 'a' parameter estimations revealed an expansion of the ceria lattice in the case of CeO 2 -TiO 2 , while a contraction is noted in the case of CeO 2 -ZrO 2 . The DRS studies suggest that the supporting oxides significantly influence the band gap energy of CeO 2 . Raman measurements disclose the presence of oxygen vacancies, lattice defects, and displacement of oxide ions from their normal lattice positions in the case of CeO 2 -TiO 2 and CeO 2 -ZrO 2 samples. The XPS studies revealed the presence of silica, titania, and zirconia in their highest oxidation states, Si(IV), Ti(IV), and Zr(IV) at the surface of the materials. Cerium is present in both Ce 4+ and Ce 3+ oxidation states. The HREM results reveal well-dispersed CeO 2 nanocrystals over the amorphous SiO 2 matrix in the case of CeO 2 -SiO 2 , isolated CeO 2 and TiO 2 (A) nanocrystals and some overlapping regions in the case of CeO 2 -TiO 2 , and nanosized CeO 2 and Ce-Zr oxides in the case of CeO 2 -ZrO 2 sample. The exact structural features of these crystals as determined by digital diffraction analysis of HREM experimental images reveal that the CeO 2 is mainly in cubic fluorite geometry. The oxygen storage capacity (OSC) as determined by thermogravimetry reveals that the OSC of mixed oxides is more than that of pure CeO 2 and the CeO 2 -ZrO 2 exhibits highest OSC.

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“…For all the prepared films, the bandgap was found in the range 2.5±3.0 eV, appreciably lower values than those expected for the bulk material. [2,5] This difference could be ascribed to oxygen deficiency, [27,79,80] Table 1). …”

Section: Optical Absorptionmentioning

confidence: 99%

Nucleation and Growth of Nanophasic CeO₂ Thin Films by Plasma‐Enhanced CVD

Barreca¹,

Gasparotto

Tondello

et al. 2003

Chemical Vapor Deposition

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Nanophasic CeO 2 -based thin films were grown at low temperatures on SiO 2 and Si(100) by plasma-enhanced (PE) CVD from a Ce IV b-diketonate first generation precursor. Film depositions were carried out in low-pressure Ar±O 2 plasmas at temperatures between 150 C and 300 C. The film microstructure was investigated by glancing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM), while the surface and in-depth chemical composition was studied by X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS), respectively. Optical properties were analyzed by UV-vis optical absorption. Nanostructured CeO 2 -based films, with crystal size less than 6 nm and a controllable Ce IV /Ce III ratio, were obtained at temperatures even lower than that required for precursor vaporization (170 C). In particular, TEM analyses showed an island growth mode and different microstructural features as a function of the substrate used.

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Optical Absorption in Cerium Dioxide Thin Films

Cited by 54 publications

References 4 publications

Gold supported CeO2/Al2O3 catalysts for CO oxidation: influence of the ceria phase

Gold supported CeO2/Al2O3 catalysts for CO oxidation: influence of the ceria phase

Nanosized CeO2–SiO2, CeO2–TiO2, and CeO2–ZrO2 Mixed Oxides: Influence of Supporting Oxide on Thermal Stability and Oxygen Storage Properties of Ceria

Nucleation and Growth of Nanophasic CeO₂ Thin Films by Plasma‐Enhanced CVD

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Optical Absorption in Cerium Dioxide Thin Films

Cited by 54 publications

References 4 publications

Gold supported CeO2/Al2O3 catalysts for CO oxidation: influence of the ceria phase

Gold supported CeO2/Al2O3 catalysts for CO oxidation: influence of the ceria phase

Nanosized CeO2–SiO2, CeO2–TiO2, and CeO2–ZrO2 Mixed Oxides: Influence of Supporting Oxide on Thermal Stability and Oxygen Storage Properties of Ceria

Nucleation and Growth of Nanophasic CeO2 Thin Films by Plasma‐Enhanced CVD

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Nucleation and Growth of Nanophasic CeO₂ Thin Films by Plasma‐Enhanced CVD