First-principles study of H intercalation in rutile<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Ti</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Koudriachova, Marina V.; Leeuw, Simon W. de; Harrison, N. M.

doi:10.1103/physrevb.70.165421

Cited by 55 publications

(28 citation statements)

References 24 publications

(33 reference statements)

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“…A few accounts of hydrogen incorporation into a rutile TiO 2 lattice have been given. [27][28][29] It remains to explain why the H-atom coverage cannot exceed a critical value and a perfect (1 1) adlayer cannot be obtained, as in the case of H on other oxide surfaces (e.g. ZnOA C H T U N G T R E N N U N G (101 0) [7] ).…”

Section: Resultsmentioning

confidence: 98%

Diffusion versus Desorption: Complex Behavior of H Atoms on an Oxide Surface

et al. 2008

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Section: Resultsmentioning

confidence: 98%

Diffusion versus Desorption: Complex Behavior of H Atoms on an Oxide Surface

et al. 2008

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“…Several studies have reported a proton-induced shallow level E P below the TiO 2 conduction band. 24,25 The residence time (t) of the electron on a trap site is calculated from the thermionic emission expression,…”

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confidence: 99%

Perturbation of the Electron Transport Mechanism by Proton Intercalation in Nanoporous TiO₂ Films

et al. 2012

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This study addresses a long-standing controversy about the electron-transport mechanism in porous metal oxide semiconductor films that are commonly used in dye-sensitized solar cells and related systems. We investigated, by temperature-dependent time-of-flight measurements, the influence of proton intercalation on the electron-transport properties of nanoporous TiO(2) films exposed to an ethanol electrolyte containing different percentages of water (0-10%). These measurements revealed that increasing the water content in the electrolyte led to increased proton intercalation into the TiO(2) films, slower transport, and a dramatic change in the dependence of the thermal activation energy (E(a)) of the electron diffusion coefficient on the photogenerated electron density in the films. Random walk simulations based on a microscopic model incorporating exponential conduction band tail (CBT) trap states combined with a proton-induced shallow trap level with a long residence time accounted for the observed effects of proton intercalation on E(a). Application of this model to the experimental results explains the conditions under which E(a) dependence on the photoelectron density is consistent with multiple trapping in exponential CBT states and under which it appears at variance with this model.

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“…In the rutile structure there are empty channels parallel to the c axis that are bounded by oxygens; the muon (hydrogen) sites are located inside these channels [28]. At these low temperatures, the muon cannot escape from the channel due to a relatively large energy barrier.…”

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Muonium donor in rutileTiO2and comparison with hydrogen

et al. 2015

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Muonium, a positive muon and an electron, is often used as an experimentally accessible substitute for hydrogen in materials research. In semiconductors and insulators, a large amount of information on the hydrogen behavior is deduced from this analogy; however, it is seldom demonstrated that this procedure is justified. We show here, via a comparison of the hyperfine interactions, that in TiO 2 muonium and hydrogen form the same configuration with the same basic electronic structure. A detailed description of the bonding characteristics of the muon to the Ti 3+ polaron is presented. The special role of muon motion within the so-called oxygen channel in the rutile structure, which occurs at a lower temperature than for hydrogen, is emphasized. Muonium (Mu) is a pseudoisotope of hydrogen in which the proton is replaced by a positive muon (μ + ), with a factor of 9 lighter mass. Muon spin spectroscopy (μSR) uses muons implanted with 100% spin polarization and offers a very sensitive method to study the properties of this isolated pseudohydrogen in solids [1,2]. It is usually assumed that information obtained from μSR can be transferred with appropriate modifications to H. However, overlapping experiments to support this assumption are scarce. A particularly relevant case is the doping character of H in semiconductors and oxides [3][4][5][6], where practically all calculations refer to the electronic structure of H whereas most experimental information comes from μSR [7][8][9][10][11][12][13]. Overlapping data exist only for ZnO where proton-ENDOR (electron-nuclear double resonance) data [14] can be compared directly with μSR results [15][16][17][18]. A number of properties (e.g., ionization energy) are indeed similar for the two species. However, the measured hyperfine interaction (hfi), scaled with the magnetic moments, differs by almost a factor of 10. This raised the question of whether the same configuration is measured, or if the H center may involve an additional defect [19,20].Here, we report a case where the same configuration can be established for H and Mu. We compare the hfi of the μSR experiment with the proton-ENDOR result, both for rutile TiO 2 . The H center in TiO 2 was extensively studied by Brant et al.[21] using electron paramagnetic resonance (EPR) and ENDOR, who found that the electron is located at the Ti ion reducing it from Ti 4+ to Ti 3+ . H is bound to one of the six O atoms surrounding Ti and the magnetic interaction between the proton and the electron is mainly dipolar. This specific hfi permits a sensitive comparison of the two experiments. We have observed a dramatic change of the μSR spectra with increasing temperature and a complete disappearance of the hyperfine splitting at 10 K. We show that this is due to rapid jumps of the muon between neighboring bonding positions to O atoms around Ti 3+ . The very strong angle dependence of the dipolar interaction and the averaging over values in different * ruivilao@fis.uc.pt positions lead to the reduction and final disappearance of the hfi...

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First-principles study of H intercalation in rutileTiO2

Cited by 55 publications

References 24 publications

Diffusion versus Desorption: Complex Behavior of H Atoms on an Oxide Surface

Diffusion versus Desorption: Complex Behavior of H Atoms on an Oxide Surface

Perturbation of the Electron Transport Mechanism by Proton Intercalation in Nanoporous TiO₂ Films

Muonium donor in rutileTiO2and comparison with hydrogen

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First-principles study of H intercalation in rutileTiO2

Cited by 55 publications

References 24 publications

Diffusion versus Desorption: Complex Behavior of H Atoms on an Oxide Surface

Diffusion versus Desorption: Complex Behavior of H Atoms on an Oxide Surface

Perturbation of the Electron Transport Mechanism by Proton Intercalation in Nanoporous TiO2 Films

Muonium donor in rutileTiO2and comparison with hydrogen

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Perturbation of the Electron Transport Mechanism by Proton Intercalation in Nanoporous TiO₂ Films