Optical constants of TiO1.7 thin films deposited by electron beam gun

Assim, E.M.

doi:10.1016/j.jallcom.2007.09.034

Cited by 27 publications

(14 citation statements)

References 26 publications

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“…the adsorbate-induced change in reflectivity, for E t,p and E n,p may change if the angle of incidence, , or the refractive index of substrate, n s , change. In our setup with =85°, R/R 0 for E t,p and E n,p can only change sign when the substrate refractive index is unphysically large n s >11.43 (the refractive index n s is expected to be approximately 1.9 and 2.4 for reduced and stoichiometric TiO 2 surfaces, respectively 52,53 ). This also implies that the critical angle of incidence for R/R 0 to change sign is ° and °, respectively, for these values of n s , i.e.…”

Section: A Polarization Angle and Substrate Dependence On Irras Meamentioning

confidence: 92%

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Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study

Mattsson

Hermansson

et al. 2014

The Journal of Chemical Physics

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Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study. Journal of Chemical Physics AbstractFormic acid (HCOOH) adsorption on rutile TiO 2 (110) has been studied by s-and p-polarized infrared reflection-absorption spectroscopy (IRRAS) and spin-polarized density functional theory together with Hubbard U contributions (DFT+U) calculations. To compare with IRRAS spectra, the results from the DFT+U calculations were used to simulate IR spectra by employing a three-layer model, where the adsorbate layer was modelled using Lorentz oscillators with calculated dielectric constants. To account for the experimental observations, four possible formate adsorption geometries were calculated, describing both the perfect (110) surface, and surfaces with defects; either O vacancies or hydroxyls. The binding energy was found to be E bind = 1.84 eV for the bridging bidentate formate species, which bonds with its IRRAS spectra measured on surfaces prepared to be either reduced, stoichiometric, or to contain surplus O adatoms, were found to be very similar. By comparisons with computed spectra, it is concluded that formate binds to in-plane Ti 5c atoms rather than to O vacancy sites. The results emphasize the importance of protonation and reactive surface hydroxylseven under UHV conditions -as reactive sites in e.g. catalytic applications.

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Section: A Polarization Angle and Substrate Dependence On Irras Meamentioning

confidence: 92%

“…For a stoichiometric surface, we use n s =2.4, and for the reduced surface, n s =1.9 is used. 52,53 The wavenumber-dependent polarizability is calculated by summation of the electronic ( e ) and the vibrational ( v ) parts of all the normal modes, expressed as Lorentz oscillators, as follows:…”

Section: Three-layer Model For Irras Spectra Simulationmentioning

confidence: 99%

Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study

Mattsson

Hermansson

et al. 2014

The Journal of Chemical Physics

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“…For dielectric surfaces, DR s remains always negative, while DR p can be negative or positive depending on the incidence angle and the refractive index n of the substrate. The refractive index decreases from 2.4 for the oxidized r-TiO 2 (110) to a value below 2.0 for the reduced one [170]. This difference in optic properties originates from the doping of TiO 2 via O vacancies created on the reduced r-TiO 2 (110) surface.…”

Section: No/tiomentioning

confidence: 96%

Vibrational spectroscopic studies on pure and metal‐covered metal oxide surfaces

Noei

Jin

Qiu

et al. 2013

Physica Status Solidi (b)

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234 3214182 y These authors contributed equally to this work.Metal oxides and metal nanoparticles dispersed on oxide substrates have gained increasing interest in surface science because of their widespread applications, especially in heterogeneous catalysis. In this review we summarize our recent vibrational spectroscopic studies on pure and metal-covered oxide surfaces (ZnO, TiO 2 , Au/ZnO and Cu/ZnO) using a number of small molecules (H 2 , CO, CO 2 , NO and HCOOH) as probes and/or reactants. High-resolution electron energy loss spectroscopy (HREELS) turned out to be a powerful tool to investigate well-defined oxide and metal/oxide model systems. The application of a novel ultrahigh vacuum IR spectroscopy (UHV-FTIRS) apparatus allowed us to record high-quality IR data on oxide surfaces of both single crystals and polycrystalline powder particles. We will particularly focus on following important issues: (i) the interaction of hydrogen with ZnO; (ii) structure and reactivity of polar and nonpolar ZnO surfaces; (iii) the role of defects in surface chemistry of oxides; (iv) the origin of significant difference in photocatalytic activity between anatase and rutile TiO 2 and (v) the interaction between metal nanoparticles and oxide supports. We will demonstrate that the data from HREELS and UHV-FTIRS provide detailed insight into structural, electronic and chemical properties of the studied systems.

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“…The properties of the investigated TiO 2 thin films could be treated as a single oscillator at wavelength λ 0 at high frequency. The high-frequency dielectric constant (ε ∞ ) can be calculated by applying the following simple classical dispersion relation [45]:…”

Section: Optical Characterizationmentioning

confidence: 99%

Phase transformation of nanostructured titanium dioxide thin films grown by sol–gel method

2012

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Nanostructured TiO 2 thin films were deposited on quartz glass at room temperature by sol-gel dip coating method. The effects of annealing temperature between 200 • C to 1100 • C were investigated on the structural, morphological, and optical properties of these films. The X-ray diffraction results showed that nanostructured TiO 2 thin film annealed at between 200 • C to 600 • C was amorphous transformed into the anatase phase at 700 • C, and further into rutile phase at 1000 • C. The crystallite size of TiO 2 thin films was increased with increasing annealing temperature. From atomic force microscopy images it was confirmed that the microstructure of annealed thin films changed from column to nubbly. Besides, surface roughness of the thin films increases from 1.82 to 5.20 nm, and at the same time, average grain size as well grows up from about 39 to 313 nm with increase of the annealing temperature. The transmittance of the thin films annealed at 1000 and 1100 • C was reduced significantly in the wavelength range of about 300-700 nm due to the change of crystallite phase. Refractive index and optical high dielectric constant of the n-TiO 2 thin films were increased with increasing annealing temperature, and the film thickness and the optical band gap of nanostructured TiO 2 thin films were decreased.

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Optical constants of TiO1.7 thin films deposited by electron beam gun

Cited by 27 publications

References 26 publications

Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study

Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study

Vibrational spectroscopic studies on pure and metal‐covered metal oxide surfaces

Phase transformation of nanostructured titanium dioxide thin films grown by sol–gel method

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