Ferroelectric-like response from the surface of SrTiO3 crystals at high temperatures

Jyotsna, Shubhra; Arora, Anu; Sekhon, Jagmeet Singh; Sheet, Goutam

doi:10.1063/1.4895484

Cited by 18 publications

(17 citation statements)

References 27 publications

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“…For the in-plane biaxial strain u < −0.02, P S //[001] is considered to exist even in the presence of quantum and thermal fluctuations at ∼40-50 K in Sec. VI C. This prediction appears consistent with the experiments for FE-like properties at RT found at the surface and in nanodots [15,16], when defect-induced strain is assumed. Therefore, the 2D electrons at the LaAlO 3 /SrTiO 3 interface [10][11][12][13][14] were considered to be due to the cooperation of the chemical doping of O vacancy and La and polar discontinuity [17,18] (Sec.…”

Section: Discussionsupporting

confidence: 89%

“…An incipient ferroelectric SrTiO 3 exhibits quantum paraelectricity as a ground-state property due to quantum mechanical fluctuations [1,2] and has intriguing properties, including a gigantic relative permittivity surpassing 10 5 [3], as well as high photolysis [4], catalysis, and electrocatalysis performance [5]. SrTiO 3 becomes ferroelectric (FE) by very small perturbations, which are manifested in the form of exotic domain walls [6], two-dimensional conduction at the insulator interface [7][8][9][10][11][12][13][14], and ferrolike properties at room temperature (RT) at surfaces and in nanodots [15,16]. Here, polar discontinuity is considered important for these conductions [7][8][9][10][11][12][13][14], providing a universal mechanism at the ferroelectric/insulator interface and the charged domain boundaries as in earlier predictions [17,18].…”

Section: Introductionmentioning

confidence: 99%

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Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Watanabe

2019

Phys. Rev. B

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The properties of stress-free and biaxially strained stoichiometric SrTiO 3 in the absence and presence of antiferrodistortive (AFD) distortion were calculated ab initio. To obtain reliable results, multiple exchange correlation (XC) functionals, including the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, were used. HSE was the primary XC functional, while another functional provided a good lower bound of ferroelectricity (FE). The reliability of the calculations was further reinforced by the calculations of the strain and AFD dependence. In contrast with previous works, we show that the ferroelectric phase (C 1 4v , C 10 4v) is more stable in the absence of quantum and thermal fluctuations than the paraelectric phase (O 1 h , D 18 4h), even for the stress-free case, and clarify the properties of these FE phases. The energy gain of stress-free FE, in comparison with the thermal and quantum fluctuation energy, indicates that a paraelectric phase emerges at room temperature by thermal fluctuations, but is near 0 K marginally close to the FE phase, which aligns with the experimental incipient FE. This implies that the paraelectricity of stress-free SrTiO 3 in experiments contains incoherent atomic-scale FE regions. These results are consistent with the FE microregions (FMR), signatures of polar disorders, and the emergence of FE in SrTiO 3 due to impurities and defects. The value of spontaneous polarization P S could reach 10 μC/cm 2 in the absence of fluctuations, even for the stress-free case. In view of the earlier theory of the carrier layer at polar discontinuities, the present results may explain the conduction at the interfaces of the LaAlO 3 /SrTiO 3. In addition, an "enhancement of FE due to symmetry constriction" is proposed as an additional mechanism to the strain-enhanced FE in the epitaxial effect. For large compressive strain, e.g., 2%, the Perdew-Burke-Ernzerhof density functional for solids (PBEsol) yielded properties with P S > 20 μC/cm 2 , agreeing with HSE, and therefore is usable as a practical substitute of HSE for SrTiO 3 .

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Watanabe

2019

Phys. Rev. B

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“…It was demonstrated e.g. in non‐ferroelectric SrTiO 3 that bias‐induced defect migration can give rise to an apparent polarization or piezoelectric hysteresis loops, which are difficult to distinguishable from true ferroelectric hysteresis loops . Nevertheless, in this case the polarization should decay with time, but as reported in Ref.…”

Section: Discussionmentioning

confidence: 84%

Comment on “Interesting Evidence for Template‐Induced Ferroelectric Behavior in Ultra‐Thin Titanium Dioxide Films Grown on (110) Neodymium Gallium Oxide Substrates”

Skiadopoulou

Kamba

Drahokoupil

et al. 2015

Adv Funct Materials

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Very recently there was a report of the discovery using piezoelectric force microscopy (PFM) of a switchable ferroelectric polarization in 1.6 % tensile strained TiO 2 thin film with anatase crystal structure (see N. Deepak et al. Adv. Funct. Mater. 2014, 24, 2844. The polarization disappeared only above 450 K, which was assigned as a Curie temperature, T C . Here we have performed X-ray diffraction, second-harmonic generation (SHG) and infrared investigations of the same films. Phonon frequencies exhibit less than a 10 % shift down with the tensile strain and no anomaly near expected T C . SHG experiment did not reveal any signal characteristic for inversion symmetry breaking, as expected in ferroelectric phase, and the clattice parameter exhibits no anomaly on heating near expected T C . Based on these results, we can summarize that we were not able to confirm the previously discovered ferroelectricity in tensile-strained anatase-TiO 2 thin films.2

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“…A sinusoidal AC voltage is applied to a piezo-chip attached to the cantilever to drive the cantilever into oscillation.The cantilever is then tuned at the contact-mode resonance frequency. All the measurements are then carried out at this resonance frequency in order to achieve maximum sensitivity 33 – 35 . In contact mode, the deflection of the cantilever is tracked while scanning it over the surface.…”

Section: Resultsmentioning

confidence: 99%

Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

Vasdev

Dutta

Mishra

et al. 2021

Sci Rep

Self Cite

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A remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250–300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + off-centering is 0.25–0.10 Å near the room temperatures (250–300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

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Ferroelectric-like response from the surface of SrTiO3 crystals at high temperatures

Cited by 18 publications

References 27 publications

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Comment on “Interesting Evidence for Template‐Induced Ferroelectric Behavior in Ultra‐Thin Titanium Dioxide Films Grown on (110) Neodymium Gallium Oxide Substrates”

Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

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