Changes in the chemical state of monocrystalline SrTiO3 surface by argon ion bombardment

Adachi, Yuka; Kohiki, Shigemi; Wagatsuma, Kazuaki; Oku, Masaoki

doi:10.1016/s0169-4332(99)00099-9

Cited by 30 publications

(29 citation statements)

References 18 publications

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“…The formation of oxygen vacancies is accompanied by a large relaxation of the first and second nearest neighbours. The localization of the electrons on titanium ions is consistent with photoemission studies on the surface of SrTiO 3 , which indicate the formation of Ti 3+ ions when surface defects are created by Ar + -ion bombardment [32].…”

Section: Resultssupporting

confidence: 78%

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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Section: Resultssupporting

confidence: 78%

First principles simulations of F centers in cubic SrTiO ₃

Carrasco

Illas

López

et al. 2005

phys. stat. sol. (c)

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“…The localization of the electrons on titanium ions is consistent with photoemission studies on the surface of SrTiO 3 , which indicate the presence of Ti 3+ ions when surface defects are created under Ar + ion bombardment. 64 Next, it is worth analyzing also the PW91 electronic structure even, as mentioned above, the systematic underestimate of the band gap implies several difficulties in the description of the electronic structure of defective SrTiO 3 . Nevertheless, to get some insight in the problem, we have analyzed the total density of states ͑DOS͒ and the atomprojected DOS of different O-deficient structures for the perfect structure and for two different O-vacancy concentrations, namely 4.0% and 0.7%; results are displayed in Fig.…”

Section: Electronic Structure Of O-deficient Srtiomentioning

confidence: 99%

First-principles calculations of the atomic and electronic structure ofFcenters in the bulk and on the (001) surface ofSrTiO3

et al. 2006

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The atomic and electronic structure, formation energy, and the energy barriers for migration have been calculated for the neutral O vacancy point defect ͑F center͒ in cubic SrTiO 3 employing various implementations of density functional theory ͑DFT͒. Both bulk and TiO 2 -terminated ͑001͒ surface F centers have been considered. Supercells of different shapes containing up to 320 atoms have been employed. The limit of an isolated single oxygen vacancy in the bulk corresponds to a 270-atom supercell, in contrast to commonly used supercells containing ϳ40-80 atoms. Calculations carried out with the hybrid B3PW functional show that the F center level approaches the conduction band bottom to within ϳ0.5 eV, as the supercell size increases up to 320 atoms. The analysis of the electronic density maps indicates, however, that this remains a small-radius center with the two electrons left by the missing O ion being redistributed mainly between the vacancy and the 3d͑z 2 ͒ atomic orbitals of the two nearest Ti ions. As for the dynamical properties, the calculated migration energy barrier in the low oxygen depletion regime is predicted to be 0.4 eV. In contrast, the surface F center exhibits a more delocalized character, which leads to significantly reduced ionization and migration energies. Results obtained are compared with available experimental data.

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“…The localization of the electrons on Ti is consistent with photoemission studies on the surface of SrTiO 3 which indicate the formation of Ti 3ϩ ions when surface defects are created by Ar ϩ -ion bombardment. 47,48 ͑3͒ The ground state of the system is nonmagnetic since the two electrons are singlet coupled ͑singlet closed-shell ground state͒. While the exact singlet-triplet separation may depend on the size of the supercell used for the calculations, the qualitative result is not, suggesting that this conclusion is not dependent on this aspect of the calculation.…”

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confidence: 99%

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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Changes in the chemical state of monocrystalline SrTiO3 surface by argon ion bombardment

Cited by 30 publications

References 18 publications

First principles simulations of F centers in cubic SrTiO ₃

First principles simulations of F centers in cubic SrTiO ₃

First-principles calculations of the atomic and electronic structure ofFcenters in the bulk and on the (001) surface ofSrTiO3

Electronic structure of a neutral oxygen vacancy inSrTiO3

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Changes in the chemical state of monocrystalline SrTiO3 surface by argon ion bombardment

Cited by 30 publications

References 18 publications

First principles simulations of F centers in cubic SrTiO 3

First principles simulations of F centers in cubic SrTiO 3

First-principles calculations of the atomic and electronic structure ofFcenters in the bulk and on the (001) surface ofSrTiO3

Electronic structure of a neutral oxygen vacancy inSrTiO3

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First principles simulations of F centers in cubic SrTiO ₃

First principles simulations of F centers in cubic SrTiO ₃