Role of oxygen vacancies on light emission mechanisms in SrTiO<sub>3</sub>induced by high-energy particles

Crespillo, Miguel L.; Graham, Joseph; Agulló‐López, F.; Zhang, Yongfeng; Weber, William J.

doi:10.1088/1361-6463/aa627f

Cited by 38 publications

(45 citation statements)

References 41 publications

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“…In particular, they have provided valuable information about the occurrence of in-gap levels for self-trapped carriers and excitons, as well as for key impurities and defects (e.g., oxygen vacancies). A variety of excitation sources, including X-rays, electrons and ion-beams have been used for comparison (see Table 1 in [32]). Depending on sample, excitation conditions, and measuring temperature, several overlapped Gaussian emissions centered at 2.0 eV, 2.5 eV, and 2.8 eV are generally distinguished [32].…”

Section: Luminescence Experimentsmentioning

confidence: 99%

“…A variety of excitation sources, including X-rays, electrons and ion-beams have been used for comparison (see Table 1 in [32]). Depending on sample, excitation conditions, and measuring temperature, several overlapped Gaussian emissions centered at 2.0 eV, 2.5 eV, and 2.8 eV are generally distinguished [32]. Remarkably, the (red) 2.0 eV band has only been clearly observed for heavily strained and amorphous samples suggesting that it is closely related to structural disorder [31,42,43].…”

Section: Luminescence Experimentsmentioning

confidence: 99%

“…The specific model for the structure of the oxygen vacancy center has been derived from detailed theoretical DFT calculations [12], which suggests the electronic structure schematically depicted in Figure 8. It corresponds to a peculiar-type of F-type center, consisting of electrons trapped at host Ti 4+ ions adjacent to an oxygen vacancy [9,32], which can be designated as Ti 3+ − V O − Ti 3+ . Other calculations using slightly different ab-initio methods [13][14][15] confirm this basic structure, although the results present somewhat different electronic features.…”

Section: Point Defects In Bulk Sto: Oxygen Vacanciesmentioning

confidence: 99%

“…More relevant for our review are the studies based on the monitoring of oxygen vacancy defects and Ti 3+ states at the surfaces and its impact on the luminescence behavior [20,21]. However, it is important to mention that the luminescence spectra and behavior observed under different excitation sources from UV light [10,17,[22][23][24][25][26][27][28][29][30] to X-rays [16], electrons [31], and ion beams [5,32], having very different penetration depths, show a similar pattern apparently associated to a bulk response. In spite of these considerations, we believe that surface luminescence is beyond the scope of our review and deserves independent attention.…”

Section: Introductionmentioning

confidence: 99%

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Recent Advances on Carrier and Exciton Self-Trapping in Strontium Titanate: Understanding the Luminescence Emissions

et al. 2019

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An up-to-date review on recent results for self-trapping of free electrons and holes, as well as excitons, in strontium titanate (STO), which gives rise to small polarons and self-trapped excitons (STEs) is presented. Special attention is paid to the role of carrier and exciton self-trapping on the luminescence emissions under a variety of excitation sources with special emphasis on experiments with laser pulses and energetic ion-beams. In spite of the extensive research effort, a definitive identification of such localized states, as well as a suitable understanding of their operative light emission mechanisms, has remained lacking or controversial. However, promising advances have been recently achieved and are the objective of the present review. In particular, significant theoretical advances in the understanding of electron and hole self-trapping are discussed. Also, relevant experimental advances in the kinetics of light emission associated with electron-hole recombination have been obtained through time-resolved experiments using picosecond (ps) laser pulses. The luminescence emission mechanisms and the light decay processes from the self-trapped excitons are also reviewed. Recent results suggest that the blue emission at 2.8 eV, often associated with oxygen vacancies, is related to a transition from unbound conduction levels to the ground singlet state of the STE. The stabilization of small electron polarons by oxygen vacancies and its connection with luminescence emission are discussed in detail. Through ion-beam irradiation experiments, it has recently been established that the electrons associated with the vacancy constitute electron polaron states (Ti3+) trapped in the close vicinity of the empty oxygen sites. These experimental results have allowed for the optical identification of the oxygen vacancy center through a red luminescence emission centered at 2.0 eV. Ab-initio calculations have provided strong support for those experimental findings. Finally, the use of Cr-doped STO has offered a way to monitor the interplay between the chromium centers and oxygen vacancies as trapping sites for the electron and hole partners resulting from the electronic excitation.

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Section: Luminescence Experimentsmentioning

confidence: 99%

Section: Luminescence Experimentsmentioning

confidence: 99%

Section: Point Defects In Bulk Sto: Oxygen Vacanciesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Recent Advances on Carrier and Exciton Self-Trapping in Strontium Titanate: Understanding the Luminescence Emissions

et al. 2019

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“…The electronic and optical behavior is presently an active and controversial field of research [6][7][8][9]. The luminescence spectra under a variety of excitation sources, including UV light [8][9][10][11][12][13][14][15][16][17][18], X-rays [19], electrons [20] and ion-beams [21,22], show three main bands centered at 2.0 eV (red), 2.5 eV (green) and 2.8 eV (blue). A detailed study using ion-beam irradiation experiments has concluded that the red band is due to d-d transitions between an excited level in the conduction band (CB) with mostly 3d(t 2g ) character and an in-gap 3d(e g ) level associated with an electron selftrapped as Ti 3+ adjacent to an oxygen vacancy (Ti 3+ -V O center) [23][24][25][26][27][28], as illustrated in Figure S1 (see supplementary data online).…”

Section: Introductionmentioning

confidence: 99%

The blue emission at 2.8 eV in strontium titanate: evidence for a radiative transition of self-trapped excitons from unbound states

Crespillo

Graham

Agulló‐López

et al. 2019

Materials Research Letters

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The origin of the blue emission in SrTiO 3 has been investigated as a function of irradiation fluence, electronic excitation density, and temperature using a range of ion energies and masses. The emission clearly does not show correlation with the concentration of vacancies generated by irradiation but is greatly enhanced under heavy-ion irradiation. The intensity ratio of the 2.8 and 2.5 eV bands is independent of fluence at all temperatures, but it increases with excitation rate. The 2.8 eV emission is proposed to correspond to a transition from conduction band states to the ground state level of the self-trapped exciton center. IMPACT STATEMENT A novel mechanism attributes the origin of the intriguing blue band in SrTiO 3 to a non-localized transition of the self-trapped exciton center from conduction band states to the ground level.

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Criteria for Efficient Photocatalytic Water Splitting Revealed by Studying Carrier Dynamics in a Model Al‐doped SrTiO₃ Photocatalyst

Li,

Takata,

Zhang

et al. 2023

Angewandte Chemie

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Overall water splitting (OWS) using semiconductor photocatalysts is a promising method for solar fuel production. Achieving a high quantum efficiency is one of the most important prerequisites for photocatalysts to realize high solar‐to‐fuel efficiency. In a recent study (Nature, 2020, 58, 411‐414), a quantum efficiency of almost 100% has been achieved in an aluminum‐doped strontium titanate (SrTiO3:Al) photocatalyst. Herein, using the SrTiO3:Al as a model photocatalyst, we reveal the criteria for efficient photocatalytic water splitting by investigating the carrier dynamics through a comprehensive photoluminescence study. It is found that the Al doping suppresses the generation of Ti3+ recombination centers in SrTiO3, the surface band bending facilitates charge separation, and the in‐situ photo‐deposited Rh/Cr2O3 and CoOOH co‐catalysts render efficient charge extraction. By suppressing photocarrier recombination and establishing a facile charge separation and extraction mechanism, high quantum efficiency can be achieved even on photocatalysts with a very short (sub‐ns) intrinsic photocarrier lifetime, challenging the belief that a long carrier lifetime is a fundamental requirement. Our findings could provide guidance on the design of OWS photocatalysts toward more efficient solar‐to‐fuel conversion.

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Role of oxygen vacancies on light emission mechanisms in SrTiO₃induced by high-energy particles

Cited by 38 publications

References 41 publications

Recent Advances on Carrier and Exciton Self-Trapping in Strontium Titanate: Understanding the Luminescence Emissions

Recent Advances on Carrier and Exciton Self-Trapping in Strontium Titanate: Understanding the Luminescence Emissions

The blue emission at 2.8 eV in strontium titanate: evidence for a radiative transition of self-trapped excitons from unbound states

Criteria for Efficient Photocatalytic Water Splitting Revealed by Studying Carrier Dynamics in a Model Al‐doped SrTiO₃ Photocatalyst

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Role of oxygen vacancies on light emission mechanisms in SrTiO3induced by high-energy particles

Cited by 38 publications

References 41 publications

Recent Advances on Carrier and Exciton Self-Trapping in Strontium Titanate: Understanding the Luminescence Emissions

Recent Advances on Carrier and Exciton Self-Trapping in Strontium Titanate: Understanding the Luminescence Emissions

The blue emission at 2.8 eV in strontium titanate: evidence for a radiative transition of self-trapped excitons from unbound states

Criteria for Efficient Photocatalytic Water Splitting Revealed by Studying Carrier Dynamics in a Model Al‐doped SrTiO3 Photocatalyst

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Product

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Role of oxygen vacancies on light emission mechanisms in SrTiO₃induced by high-energy particles

Criteria for Efficient Photocatalytic Water Splitting Revealed by Studying Carrier Dynamics in a Model Al‐doped SrTiO₃ Photocatalyst