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Visible-light-accelerated oxygen vacancy migration in strontium titanate.

Li Y, Lei Y, Shen BG, Sun JR - Sci Rep (2015)

Bottom Line: There is evidence that most of the attractive properties of SrTiO3 are closely associated with oxygen vacancies.Tuning the kinetics of oxygen vacancies is then highly desired.This effect provides a feasible approach towards the modulation of the anionic processes.

View Article: PubMed Central - PubMed

Affiliation: Beijing National Laboratory for Condensed Matter &Institute of Physics, Chinese Academy of Sciences, Beijing 100190, Peoples' Republic of China.

ABSTRACT
Strontium titanate is a model transition metal oxide that exhibits versatile properties of special interest for both fundamental and applied researches. There is evidence that most of the attractive properties of SrTiO3 are closely associated with oxygen vacancies. Tuning the kinetics of oxygen vacancies is then highly desired. Here we reported on a dramatic tuning of the electro-migration of oxygen vacancies by visible light illumination. It is found that, through depressing activation energy for vacancy diffusion, light illumination remarkably accelerates oxygen vacancies even at room temperature. This effect provides a feasible approach towards the modulation of the anionic processes. The principle proved here can be extended to other perovskite oxides, finding a wide application in oxide electronics.

No MeSH data available.


Related in: MedlinePlus

Schematic diagram for the migration of oxygen vacancies under electrical field and Light illumination.(a) Lattice deformation occurs accompanying the electro-migration of oxygen vacancies without light illumination. Oxygen vacancies near the STO surface may group into VO-complexes (for example, VO-Ti-VO chains), and have a high activation energy for diffusion. As a consequence, the field-induced lattice change cannot be detected in the time window of the XRD experiments. (b) Photo-excitation of bounded electrons in the VO-complex leads to the disassembly of the VO-complexes, making oxygen vacancies much more mobile. Arrows mark the velocity of VOs in electrical field.
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f4: Schematic diagram for the migration of oxygen vacancies under electrical field and Light illumination.(a) Lattice deformation occurs accompanying the electro-migration of oxygen vacancies without light illumination. Oxygen vacancies near the STO surface may group into VO-complexes (for example, VO-Ti-VO chains), and have a high activation energy for diffusion. As a consequence, the field-induced lattice change cannot be detected in the time window of the XRD experiments. (b) Photo-excitation of bounded electrons in the VO-complex leads to the disassembly of the VO-complexes, making oxygen vacancies much more mobile. Arrows mark the velocity of VOs in electrical field.

Mentions: All of our experiments were conducted near room temperature. In this case, the content of singly ionized vacancies could be considerable. As well documented15161930, singly ionized vacancies prefer to form VO-complexes by sharing their electrons with the two closest titanium atoms, yielding in-gap states (Fig. 4a). In fact, VO-complexes in the form of Ti3+-VO or VO-Ti-VO pairs have been proposed13151619. Presumably, the EA of these VO-complexes could be significantly larger than that of VO••s (ref. 9). Various experiments have shown that EA is ~0.6 eV for VO•• and ~1 eV for VO-complexes151920. Since the photon energy used here is much lower than the band gap of STO, photo-illumination will only affect the VO-complexes, exciting the shared electrons to the conduction band of STO. Without the shared electrons, however, the VO-complexes become unstable, disassembling into isolated VO••s (Fig. 4b). In this manner, photo-excitation accelerates the VO diffusion thus the gating effect. This inference is in consistent with the observed illumination-induced reduction of EA shown in Fig. 3d,f. To summarize, the present work reveals the close relation between photo-excitation and oxygen vacancy diffusion, paving the way towards the tuning of the anionic processes which could be important for oxide electronics.


Visible-light-accelerated oxygen vacancy migration in strontium titanate.

Li Y, Lei Y, Shen BG, Sun JR - Sci Rep (2015)

Schematic diagram for the migration of oxygen vacancies under electrical field and Light illumination.(a) Lattice deformation occurs accompanying the electro-migration of oxygen vacancies without light illumination. Oxygen vacancies near the STO surface may group into VO-complexes (for example, VO-Ti-VO chains), and have a high activation energy for diffusion. As a consequence, the field-induced lattice change cannot be detected in the time window of the XRD experiments. (b) Photo-excitation of bounded electrons in the VO-complex leads to the disassembly of the VO-complexes, making oxygen vacancies much more mobile. Arrows mark the velocity of VOs in electrical field.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588568&req=5

f4: Schematic diagram for the migration of oxygen vacancies under electrical field and Light illumination.(a) Lattice deformation occurs accompanying the electro-migration of oxygen vacancies without light illumination. Oxygen vacancies near the STO surface may group into VO-complexes (for example, VO-Ti-VO chains), and have a high activation energy for diffusion. As a consequence, the field-induced lattice change cannot be detected in the time window of the XRD experiments. (b) Photo-excitation of bounded electrons in the VO-complex leads to the disassembly of the VO-complexes, making oxygen vacancies much more mobile. Arrows mark the velocity of VOs in electrical field.
Mentions: All of our experiments were conducted near room temperature. In this case, the content of singly ionized vacancies could be considerable. As well documented15161930, singly ionized vacancies prefer to form VO-complexes by sharing their electrons with the two closest titanium atoms, yielding in-gap states (Fig. 4a). In fact, VO-complexes in the form of Ti3+-VO or VO-Ti-VO pairs have been proposed13151619. Presumably, the EA of these VO-complexes could be significantly larger than that of VO••s (ref. 9). Various experiments have shown that EA is ~0.6 eV for VO•• and ~1 eV for VO-complexes151920. Since the photon energy used here is much lower than the band gap of STO, photo-illumination will only affect the VO-complexes, exciting the shared electrons to the conduction band of STO. Without the shared electrons, however, the VO-complexes become unstable, disassembling into isolated VO••s (Fig. 4b). In this manner, photo-excitation accelerates the VO diffusion thus the gating effect. This inference is in consistent with the observed illumination-induced reduction of EA shown in Fig. 3d,f. To summarize, the present work reveals the close relation between photo-excitation and oxygen vacancy diffusion, paving the way towards the tuning of the anionic processes which could be important for oxide electronics.

Bottom Line: There is evidence that most of the attractive properties of SrTiO3 are closely associated with oxygen vacancies.Tuning the kinetics of oxygen vacancies is then highly desired.This effect provides a feasible approach towards the modulation of the anionic processes.

View Article: PubMed Central - PubMed

Affiliation: Beijing National Laboratory for Condensed Matter &Institute of Physics, Chinese Academy of Sciences, Beijing 100190, Peoples' Republic of China.

ABSTRACT
Strontium titanate is a model transition metal oxide that exhibits versatile properties of special interest for both fundamental and applied researches. There is evidence that most of the attractive properties of SrTiO3 are closely associated with oxygen vacancies. Tuning the kinetics of oxygen vacancies is then highly desired. Here we reported on a dramatic tuning of the electro-migration of oxygen vacancies by visible light illumination. It is found that, through depressing activation energy for vacancy diffusion, light illumination remarkably accelerates oxygen vacancies even at room temperature. This effect provides a feasible approach towards the modulation of the anionic processes. The principle proved here can be extended to other perovskite oxides, finding a wide application in oxide electronics.

No MeSH data available.


Related in: MedlinePlus