Study of intrinsic point defects in oxides of the perovskite family: II. Experiment

Raevski, I. P.; Maksimov, S M; Fisenko, A. V.; Prosandeyev, S. A.; Osipenko, I. A.; Tarasenko, P. F.

doi:10.1088/0953-8984/10/36/012

Cited by 47 publications

(36 citation statements)

References 24 publications

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“…This is consistent with previous theoretical studies 6 and with experimental estimates which indicated a very small ionization energy for the oxygen vacancy, of the order of 0.4 eV. 44 Optical measurements suggest that the presence of oxygen vacancies induce states slightly below the conduction band edge, 45 although these assignments are not unambiguous.…”

Section: Discussionsupporting

confidence: 89%

“…5, show that by creating the vacancy, a new occupied state appears in the gap, at 3.4 eV above the top of the valence band and 0.8 eV below the bottom of the conduction band ͑singlet state͒. This is consistent with experimental estimates which indicated an ionization energy for the neutral oxygen vacancy of the order of 0.4 eV, 44 and with optical measurements which suggest the presence vacancies-induced states slightly below the conduction band edge. 45 A second empty state is very close to the first one, Fig.…”

Section: The Neutral O Vacancy In Srtio 3 : Periodic Calculationssupporting

confidence: 81%

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Electronic structure of a neutral oxygen vacancy inSrTiO3

et al. 2003

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The electronic structure of an isolated oxygen vacancy in SrTiO 3 has been investigated with a variety of ab initio quantum mechanical approaches. In particular we compared pure density functional theory ͑DFT͒ approaches with the Hartree-Fock method, and with hybrid methods where the exchange term is treated in a mixed way. Both local cluster models and periodic calculations with large supercells containing up to 80 atoms have been performed. Both diamagnetic ͑singlet state͒ and paramagnetic ͑triplet state͒ solutions have been considered. We found that the formation of an O vacancy is accompanied by the transfer of two electrons to the 3d(z 2 ) orbitals of the two Ti atoms along the Ti-Vac-Ti axis. The two electrons are spin coupled and the ground state is diamagnetic. New states associated with the defect center appear in the gap just below the conduction band edge. The formation energy computed with respect to an isolated oxygen atom in the triplet state is 9.4 eV.

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Section: Discussionsupporting

confidence: 89%

Section: The Neutral O Vacancy In Srtio 3 : Periodic Calculationssupporting

confidence: 81%

Electronic structure of a neutral oxygen vacancy inSrTiO3

et al. 2003

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“…Due to existence of different kinds of bonds in SrTiO 3 one can observe a competition between the tendency to trap the electrons associated with the missing oxygen in vacancy (F center) or to localize them on the Ti 3d orbitals. The creation of a neutral O vacancy results in the new electronic state below the conduction band, which is consistent with experimental estimate indicated small ionization energy for the oxygen vacancy [30]. Defect band is mainly composed of 3d(z 2 ) energy levels of the two Ti ions directly above and below the vacancy.…”

Section: Discussionsupporting

confidence: 88%

First principles simulations of F centers in cubic SrTiO ₃

Carrasco

Illas

López

et al. 2005

phys. stat. sol. (c)

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Atomic and electronic structure of regular and O-deficient SrTiO 3 have been studied. Several types of first principles atomistic simulations: Hartree-Fock method, Density Functional Theory, and hybrid HF-DFT functionals, have been applied to periodic models that consider supercells of different sizes (ranging between 40 and 240 atoms). We confirm the ionic character of the Sr-O bonds and the high covalency of the Ti-O 2 substructure. For the stoichiometric cubic crystal; the lattice constant and bulk modulus correctly reproduce the experimental data whereas the band gap is only properly obtained by the B3PW functional. The relaxed geometry around the F center shows a large expansion of the two nearest Ti ions. Moreover, the vacancy formation energy is extremely sensitive to the size and the shape of the supercell as well as the calculation method. The electronic density map indicates the redistribution of two electrons of the missing O atom between the vacancy and 3d atomic orbitals of the two nearest Ti ions, in contrast to the F centers in ionic oxides where the charge centroid does not change.

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“…Recent experimental work by Raevski et al [35] has found that the neutral oxygen vacancy is at a shallow level with an energy of several meV in BaTiO 3 and SrTiO 3 and the singly charged oxygen vacancy is a relatively deep level at 0.5-0.6 eV and 0.3-0.4 eV below the conduction band minimum (CBM) in BaTiO 3 and SrTiO 3 , respectively. Mizushima et al also found singly charged oxygen vacancies residing at a energy level of 0.2-0.3 eV in La (donor)-doped SrTiO 3 [36].…”

Section: Resultsmentioning

confidence: 99%