Structural properties and electrical characteristics of high-k Tm2Ti2O7 gate dielectrics

Pan, Tung-Ming; Yen, Li-Chen

doi:10.1016/j.apsusc.2009.10.017

Cited by 8 publications

(4 citation statements)

References 16 publications

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“…2 shows the spectrum of O 1s for the 4.5 atom % Tm-doped TiO 2 sample annealed at 973 K in which a new contribution to the O 1s signal was observed at a BE of 530.8 eV. This signal is assigned to O 2− in the Tm 2 Ti 2 O 7 pyrochlore lattice [32]. Fig.…”

Section: Resultsmentioning

confidence: 99%

Tm-doped TiO₂ and Tm₂Ti₂O₇ pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Santos¹,

Navas²,

Aguilar³

et al. 2015

Beilstein J. Nanotechnol.

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SummaryTm-doped TiO2 nanoparticles were synthesized using a water-controlled hydrolysis reaction. Analysis was performed in order to determine the influence of the dopant concentration and annealing temperature on the phase, crystallinity, and electronic and optical properties of the resulting material. Various characterization techniques were utilized such as X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and UV–vis spectroscopy. For the samples annealed at 773 and 973 K, anatase phase TiO2 was obtained, predominantly internally doped with Tm3+. ICP–AES showed that a doping concentration of up to 5.8 atom % was obtained without reducing the crystallinity of the samples. The presence of Tm3+ was confirmed by X-ray photoelectron spectroscopy and UV–vis spectroscopy: the incorporation of Tm3+ was confirmed by the generation of new absorption bands that could be assigned to Tm3+ transitions. Furthermore, when the samples were annealed at 1173 K, a pyrochlore phase (Tm2Ti2O7) mixed with TiO2 was obtained with a predominant rutile phase. The photodegradation of methylene blue showed that this pyrochlore phase enhanced the photocatalytic activity of the rutile phase.

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Section: Resultsmentioning

confidence: 99%

Tm-doped TiO₂ and Tm₂Ti₂O₇ pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Santos¹,

Navas²,

Aguilar³

et al. 2015

Beilstein J. Nanotechnol.

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“…In turn, the patterns obtained showed that anatase was the predominant phase in the samples annealed at 773 and 973 K in most cases, while rutile was the predominant phase in the samples annealed at 1173 K. So, the Tm 3+ ion may have been incorporated into the anatase structure but not the rutile one, probably because the ionic radius of Tm 3+ is considerably larger than that of Ti 4+ (r(Ti 4+ ) = 0.68 Å; r(Tm 3+ ) = 0.994 Å), 28 and the anatase structure is less dense than the rutile one. Moreover, Shlyakhtina et al reported fluorite-pyrochlore-fluorite phase transitions for Ln 2 Ti 2 O 7 (Ln = Lu, Yb, Tm), and that the pyrochlore structure is formed at T > 1073 K. 26 Typically, pyrochlore compounds (based on rare earths, that is, Ln 2 Ti 2 O 7 ) are obtained by solidstate reactions at elevated temperatures, 25,29 rf cosputtering deposition, 30,31 and hydroxide coprecipitation followed by freeze-drying. 26,32 In our case, the pyrochlore structure Tm 2 Ti 2 O 7 was obtained using a solution-based method of synthesis.…”

Section: Xrdmentioning

confidence: 99%

Thermo-selective Tm_xTi_1−xO_2−x/2nanoparticles: from Tm-doped anatase TiO₂to a rutile/pyrochlore Tm₂Ti₂O₇mixture. An experimental and theoretical study with a photocatalytic application

et al. 2014

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This is an experimental and theoretical study of thulium doped TiO2 nanoparticles. From an experimental perspective, a method was used to synthesize thulium-doped TiO2 nanoparticles in which Tm(3+) replaces Ti(4+) in the lattice, which to our knowledge has neither been reported nor studied theoretically so far. Different proportions of anatase and rutile phases were obtained at different annealing temperatures, and XRD and Raman spectroscopy also revealed the presence of a pyrochlore phase (Tm2Ti2O7) at 1173 K. Thus, the structure of the Tm-doped nanoparticles was thermally-controlled. Furthermore, XPS showed the presence of Tm(3+) in the samples synthesized, which produces oxygen vacancies to maintain the local neutrality in the lattice. The presence of Tm(3+) in the samples led to changes in the UV-Vis absorption spectra, so they showed photoluminescence properties and new states in the band gap, which produce a new lower energy electronic transition than the main TiO2 one. Periodic DFT calculations were performed to understand the experimentally produced structures. The production of oxygen vacancies was analysed and the changes generated in the structure were fully detailed. The DOS and PDOS analyses confirmed the experimental results obtained using UV-Vis spectroscopy, and showed that the new electronic states in the band gap are due to interactions of the f state of Tm and the p state of O. Likewise, the charge study and the ELF analysis indicate that when Tm is introduced into the TiO2 structure, the Ti-O bond around the oxygen vacancy is strengthened. Finally, an example of a photocatalytic application was developed to show the high efficiency of the samples due to the heterojunction in the interfaces of the phases in the samples, which improved the charge separation and the good charge carrier mobility due to the presence of the pyrochlore phase, as was also shown theoretically.

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“…This can be studied from the O 1s XPS spectra. [32]. Figure 2d demonstrates how the amount of O in the adsorbed species increases with the Tm concentration.…”

Section: X-ray Photoelectron Spectroscopymentioning

confidence: 95%

Tm-doped TiO2 and Tm2Ti2O7 pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Santos¹,

Navas²,

Aguilar³

et al. 2016

Nano Online

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Tm-doped TiO 2 nanoparticles were synthesized using a water-controlled hydrolysis reaction. Analysis was performed in order to determine the influence of the dopant concentration and annealing temperature on the phase, crystallinity, and electronic and optical properties of the resulting material. Various characterization techniques were utilized such as X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. For the samples annealed at 773 and 973 K, anatase phase TiO 2 was obtained, predominantly internally doped with Tm 3+. ICP-AES showed that a doping concentration of up to 5.8 atom % was obtained without reducing the crystallinity of the samples. The presence of Tm 3+ was confirmed by X-ray photoelectron spectroscopy and UV-vis spectroscopy: the incorporation of Tm 3+ was confirmed by the generation of new absorption bands that could be assigned to Tm 3+ transitions. Furthermore, when the samples were annealed at 1173 K, a pyrochlore phase (Tm 2 Ti 2 O 7) mixed with TiO 2 was obtained with a predominant rutile phase. The photodegradation of methylene blue showed that this pyrochlore phase enhanced the photocatalytic activity of the rutile phase.

show abstract

Structural properties and electrical characteristics of high-k Tm2Ti2O7 gate dielectrics

Cited by 8 publications

References 16 publications

Tm-doped TiO₂ and Tm₂Ti₂O₇ pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Tm-doped TiO₂ and Tm₂Ti₂O₇ pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Thermo-selective Tm_xTi_1−xO_2−x/2nanoparticles: from Tm-doped anatase TiO₂to a rutile/pyrochlore Tm₂Ti₂O₇mixture. An experimental and theoretical study with a photocatalytic application

Tm-doped TiO2 and Tm2Ti2O7 pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

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Structural properties and electrical characteristics of high-k Tm2Ti2O7 gate dielectrics

Cited by 8 publications

References 16 publications

Tm-doped TiO2 and Tm2Ti2O7 pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Tm-doped TiO2 and Tm2Ti2O7 pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Thermo-selective TmxTi1−xO2−x/2nanoparticles: from Tm-doped anatase TiO2to a rutile/pyrochlore Tm2Ti2O7mixture. An experimental and theoretical study with a photocatalytic application

Tm-doped TiO2 and Tm2Ti2O7 pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

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Tm-doped TiO₂ and Tm₂Ti₂O₇ pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Tm-doped TiO₂ and Tm₂Ti₂O₇ pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

Thermo-selective Tm_xTi_1−xO_2−x/2nanoparticles: from Tm-doped anatase TiO₂to a rutile/pyrochlore Tm₂Ti₂O₇mixture. An experimental and theoretical study with a photocatalytic application