Hydrogen donors and Ti3+ ions in reduced TiO2 crystals

Brant, A. T.; Yang, Shan; Giles, N. C.; Halliburton, L. E.

doi:10.1063/1.3630964

Cited by 48 publications

(46 citation statements)

References 27 publications

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“…This idea is consistent with EPR results 7,8 that exhibit such localization on two distinctly different Ti atoms, depending on whether the electron comes from H i or from substitutional F. The differences between the energies found by theory for configurations with the electron localized on different Ti are too small for theory to reliably determine their order. 32 So the guidance of theory is general and not specific.…”

supporting

confidence: 75%

“…6 Furthermore, recent EPR experiments on neutral H i as well as on F substituting for O in mildly reduced TiO 2 show a characteristic that is unusual in most materials, especially semiconductors: the spin associated with the unpaired electron in each case is localized on a single Ti, rather than being spread out over many sites. 7,8 Finally, while the classic vibrational spectra reported by Bates and Perkins 6 show a single sharp line for each isotope (2445 cm -1 for OD), more recent results of Herklotz et al 9 reveal IR lines for OD at 2445.0, 2445.7, and 2447.8 cm -1 whose relative intensities are strongly dependent on temperature. Herklotz et al have proposed that the OD center (and also OH) is a shallow donor and have assigned the multiline structure to its two different charge states.…”

Section: Introductionmentioning

confidence: 99%

“…4 to explain our experimental data, we propose that for E 1 the electron is localized on Ti 1 , consistent with EPR studies of neutral H at low temperature. 8 For E 2 it is localized on Ti 2 . For E 3 it is localized on Ti 3 or Ti 3 ', or on any one of many more distant Ti.…”

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confidence: 99%

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Small polaron characteristics of an OD center in TiO2studied by infrared spectroscopy

2012

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Small polaron characteristics of an OD center in TiO2studied by infrared spectroscopy

2012

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“…The two pairs of satellite lines are due to Mu with different hfi, corresponding to Mu in the two orientationally inequivalent sublattices of the rutile structure. Figure 2 We begin by comparing (Table I) the present results with the ENDOR hydrogen data [21] accounting for differences in the magnetic moments of the muon and proton (ratio 3.183). We calculated the line positions with the scaled hfi parameters of the ENDOR experiment, and compared these with the present data.…”

mentioning

confidence: 99%

“…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.…”

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confidence: 99%

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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