Theoretical study of F-type color center in rutile TiO2

Chen, J.; Lin, Liangcai; Jing, Fuqian

doi:10.1016/s0022-3697(01)00018-x

Cited by 98 publications

(60 citation statements)

References 19 publications

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“…Regarding the F-type center, optical bands consist of three centers: pure oxygen vacancy (F 2+ ), single-electron-trapped oxygen vacancy (F + ), and two-electron-trapped oxygen vacancy (F). The calculated optical band of R-TiO 2 is at ∼760 nm for F + -center and ∼1.7 μm for F-center (22), whereas the F 2+ -center state is even closer to the conduction band. Notice that the energetic depth of F-and F 2+ -centers roughly matches the defect states that are related to the shallow electron traps (23) including Ti 3+ (20,21).…”

Section: Significancementioning

confidence: 85%

Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons

Lee

Kim

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Titania, which exhibits superwetting under light illumination, has been widely used as an ideal material for environmental solution such as self-cleaning, water-air purification, and antifogging. There have been various studies to understand such superhydrophilic conversion. The origin of superwetting has not been clarified in a unified mechanism yet, which requires direct experimental investigation of the dynamic processes of water-layer growth. We report in situ measurements of the growth rate and height of the photo-adsorbed water layers by tip-based dynamic force microscopy. For nanocrystalline anatase and rutile TiO 2 we observe light-induced enhancement of the rate and height, which decrease after O 2 annealing. The results lead us to confirm that the long-range attraction between water molecules and TiO 2 , which is mediated by delocalized electrons in the shallow traps associated with O 2 vacancies, produces photo-adsorption of water on the surface. In addition, molecular dynamics simulations clearly show that such photo-adsorbed water is critical to the zero contact angle of a water droplet spreading on it. Therefore, we conclude that this "water wets water" mechanism acting on the photoadsorbed water layers is responsible for the light-induced superwetting of TiO 2 . Similar mechanism may be applied for better understanding of the hydrophilic conversion of doped TiO 2 or other photo-catalytic oxides.

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Section: Significancementioning

confidence: 85%

Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons

Lee

Kim

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…4(b), the Nb-only doped and (Nb þ In) co-doped TiO 2 are all dark blue, being associated with the F-type color center (generated by the combination of oxygen vacancy and Ti 3þ ions) in the rutile TiO 2 structure. 31 In contrast, the pure rutile TiO 2 and In-only doped rutile TiO 2 are milky white, demonstrating that the oxygen vacancies generated during the high-temperature-sintering process cannot induce enough Ti 3þ ions to change the color of rutile TiO 2 .…”

Section: B Valence State Measurementsmentioning

confidence: 99%

Microstructure and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

Zhuang

et al. 2014

Journal of Applied Physics

140

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The (Nb + In) co-doped TiO2 ceramics recently attracted considerable attention due to their colossal dielectric permittivity (CP) (∼100,000) and low dielectric loss (∼0.05). In this research, the 0.5 mol. % In-only, 0.5 mol. % Nb-only, and 0.5–7 mol. % (Nb + In) co-doped TiO2 ceramics were synthesized by standard conventional solid-state reaction method. Microstructure studies showed that all samples were in pure rutile phase. The Nb and In ions were homogeneously distributed in the grain and grain boundary. Impedance spectroscopy and I-V behavior analysis demonstrated that the ceramics may compose of semiconducting grains and insulating grain boundaries. The high conductivity of grain was associated with the reduction of Ti4+ ions to Ti3+ ions, while the migration of oxygen vacancy may account for the conductivity of grain boundary. The effects of annealing treatment and bias filed on electrical properties were investigated for co-doped TiO2 ceramics, where the electric behaviors of samples were found to be susceptible to the annealing treatment and bias field. The internal-barrier-layer-capacitance mechanism was used to explain the CP phenomenon, the effect of annealing treatment and nonlinear I-V behavior for co-doped rutile TiO2 ceramics. Compared with CaCu3Ti4O12 ceramics, the high activation energy of co-doped rutile TiO2 (3.05 eV for grain boundary) was thought to be responsible for the low dielectric loss.

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“…[20][21][22][23] Several theoretical investigations, mainly based on density functional theory (DFT), 24 have also been reported. 4,21,[25][26][27][28][29][30][31][32][33][34][35][36][37][38] In terms of the electronic structure, three main questions related to vacancies are (1) what is the orbital composition of an V o -induced state; (2) is it an in-gap state or a conduction band resonance; and (3) does a vacancy possess a net magnetic moment? All three questions can in principle be answered by density functional theory.…”

Section: Introductionmentioning

confidence: 99%

Localized states induced by an oxygen vacancy in rutile TiO2

Lin

Shin

Demkov

2015

Journal of Applied Physics

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Using density functional theory and model Hamiltonian analysis, we investigate the localized states induced by an oxygen vacancy in rutile TiO 2 . We identify two classes of localized states-the hybrid and the polaron. The hybrid state is caused by the orbital overlap between three Ti atoms next to a vacancy and is mainly derived from the Ti e g orbitals. The polaron state is caused by the local lattice distortion and is mainly composed of one particular t 2g orbital from a single Ti atom. The first principles calculation shows that the polaron state is energetically favored, and the tight-binding analysis reveals the underlying connection between the bulk band structure and the orbital character of the polaron. The magnetic coupling between two nearby polaron states is found to be ferromagnetic. Using this picture, we analyze the results of recent theoretical calculations and experiments and discuss the connection to vacancies in SrTiO 3 . V C 2015 AIP Publishing LLC. [http://dx.

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Theoretical study of F-type color center in rutile TiO2

Cited by 98 publications

References 19 publications

Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons

Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons

Microstructure and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

Localized states induced by an oxygen vacancy in rutile TiO2

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Theoretical study of F-type color center in rutile TiO2

Cited by 98 publications

References 19 publications

Superwetting of TiO 2 by light-induced water-layer growth via delocalized surface electrons

Superwetting of TiO 2 by light-induced water-layer growth via delocalized surface electrons

Microstructure and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

Localized states induced by an oxygen vacancy in rutile TiO2

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Product

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Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons

Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons