Ferroelectricity Induced by Oxygen Isotope Exchange in Strontium Titanate Perovskite

Itoh, Makoto; Wang, R.; Inaguma, Yoshiyuki; Yamaguchi, Toshihisa; Shan, Yue Jin; Nakamura, Tetsurō

doi:10.1103/physrevlett.82.3540

Cited by 555 publications

(430 citation statements)

References 20 publications

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“…It is well known that STO is a quantum paraelectric where the onset of ferroelectric order is suppressed by quantum fluctuations 17 . In such ferroelectric-like materials, the free energy density F can be expressed by the Landau-Ginzburg theory as a power-series expansion of the polarization P 18 :…”

Section: A Nonlinear Dielectric Responsementioning

confidence: 99%

Collapse of electrons to a donor cluster inSrTiO3

Reich

Shklovskiǐ

2015

Phys. Rev. B

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It is known that a nucleus with charge Ze, where Z > 170 creates electron-positron pairs from the vacuum. Electrons collapse onto the nucleus resulting in a net charge Zn < Z while the positrons are emitted. This effect is due to the relativistic dispersion law. The same reason leads to the collapse of electrons to the donor cluster with a large charge number Z in narrow-band gap semiconductors, Weyl semimetals and graphene. In this paper, a similar effect of electron collapse and charge renormalization is found for a donor cluster in SrTiO3 (STO), but with a different origin. At low temperatures, STO has an enormously large dielectric constant and the nonlinear dielectric response becomes dominant when the electric field is still small. This leads to the collapse of electrons into a charged spherical donor cluster with radius R when its total charge number Z exceeds a critical value Zc R/a where a is the lattice constant. The net charge Zne grows with Z until Z exceeds Z * (R/a) 9/7 . After this point, the charge of the compact core Zn remains Z * , while the rest Z * electrons form a sparse Thomas-Fermi electron atmosphere around it. We show that the thermal ionization of such two-scale atoms easily strips the outer atmosphere while the inner core remains preserved. We extend our results to the case of long cylindrical clusters. We discuss how our predictions can be tested by measuring conductivity of chain of discs of charge on the STO surface.

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Section: A Nonlinear Dielectric Responsementioning

confidence: 99%

Collapse of electrons to a donor cluster inSrTiO3

Reich

Shklovskiǐ

2015

Phys. Rev. B

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“…3,4 The investigation of the thin film growth and the properties of this homologous series is highly necessary in the sense that the n = ϱ member, SrTiO 3 , shows a variety of physical properties such as high Hall mobility at low temperature, 5 superconductivity, 6 large thermoelectric transport, 7 and ferroelectricity. 8,9 SrTiO 3 is, however, the only member of the series that melts congruently. Therefore single crystal of other members has been not reported.…”

Section: Sr 2 Tio 4 Layered Perovskite Thin Films Grown By Pulsed Lasmentioning

confidence: 99%

Sr2TiO4 layered perovskite thin films grown by pulsed laser deposition

Shibuya

Jia

et al. 2008

Appl. Phys. Lett.

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“…1,2 STO is also a perfect prototype to investigate phase transition, 3 especially to understand the surface and interface structural configuration for the perovskite films grown on it. 4 Although ferroelectric properties were only reported through oxygen isotope exchange ͑ST 18 O͒, 3,5 and cation substitution, 6,7 recent theories and experiments validate the existence of ferroeletricity in STO thin films under strain. [8][9][10] He et al [11][12][13] systematically studied the structural phase transition of STO thin films under strain.…”

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confidence: 99%

Strain distribution in epitaxial SrTiO3 thin films

Zhai

Jiang

et al. 2006

Applied Physics Letters

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The lattice strain distributions of epitaxial SrTiO 3 films deposited on LaAlO 3 were investigated by in situ x-ray diffraction at the temperature range of 25-300 K, grazing incident x-ray diffraction, and high resolution x-ray diffraction. The nearly linear temperature dependence of the out-of-plane lattice constant of SrTiO 3 was observed in the measured temperature range. The depth distribution of the lattice strain at room temperature for SrTiO 3 films includes the surface layer, strained layer, and interface layer. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2424282͔ SrTiO 3 ͑STO͒ is an incipient ferroelectric material in perovskite structure, which has been extensively studied for its application in tunable microwave devices for having a large and variable dielectric constant. 1,2 STO is also a perfect prototype to investigate phase transition, 3 especially to understand the surface and interface structural configuration for the perovskite films grown on it. 4 Although ferroelectric properties were only reported through oxygen isotope exchange ͑ST 18 O͒, 3,5 and cation substitution, 6,7 recent theories and experiments validate the existence of ferroeletricity in STO thin films under strain. [8][9][10] He et al. [11][12][13] systematically studied the structural phase transition of STO thin films under strain. Devonshire 14 predicted the shift of the ferroelectric phase transition temperature ͑T c ͒ for STO thin films due to the biaxial strain. Haeni et al. 10 reported that the room temperature ferroelectricity appears for the tensile strained STO thin films on DyScO 3 substrates, although STO crystal is incipient ferroelectric. There is little work on the observation of distribution of lattice strain along the normal of sample surface for STO thin films.In this letter, the distribution of the lattice strain of the epitaxial STO films grown on LaAlO 3 ͑LAO͒ ͑001͒ substrate by laser molecular beam epitaxy ͑MBE͒ deposition ͑L-MBE͒ is investigated. The temperature dependence of the c-direction lattice constant ͑c-T curve͒ is nearly linear, which is different from that of the bulk. The depth dependence of the lattice strain is not homogeneous, which may be due to the competition between the elastic restore and the lattice mismatch between STO film and LAO substrate.STO films were grown on LAO ͑001͒ single crystal substrate in a L-MBE system. The technique was used to deposit STO on Si in our previous studies. 15,16 Briefly, a single crystal STO target was used to grow STO film. A KrF excimer laser was used in a repetition rate of 2 Hz. The substrate was heated to 770°C. The film thicknesses were 80, 150, and 280 nm from the measurement of a Dektax 3 ST surface profile. X-ray diffraction ͑XRD͒ ͑Cu K␣ radiation͒ analysis was performed using the /2 scan mode on a Rigaku Dmax-rB and a Bruker Advanced D8 X-ray diffractometer. The depth dependence of strain, which is related to the film thickness, was determined by grazing incident x-ray diffraction ͑surface x-ray diffraction͒, which was carried out on Be...

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Ferroelectricity Induced by Oxygen Isotope Exchange in Strontium Titanate Perovskite

Cited by 555 publications

References 20 publications

Collapse of electrons to a donor cluster inSrTiO3

Collapse of electrons to a donor cluster inSrTiO3

Sr2TiO4 layered perovskite thin films grown by pulsed laser deposition

Strain distribution in epitaxial SrTiO3 thin films

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