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Cited by 14Ferroelectric and Piezoelectric MaterialsPhotorefractive and Nonlinear OpticsMultiferroics and related materials

Enhancement of Electro-Optic Response in BaTiO3 Films Integrated on Si via Heating and Cooling Rate Control

Open access
Reynaud, Marc, Waqar, Moaz, Du, Chaojie, Posadas, Agham B., Pan, Xiaoqing, Demkov, Alexander A.·2025·Communications Materials
DOI 10.1038/s43246-025-00908-x
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Abstract

Recent advancements in BaTiO3-based Si-integrated photonics devices have shown very large electro-optic responses, allowing for aggressive device scaling in both size and power. However, control of the crystallographic domain structure of high-quality epitaxial BaTiO3 films still remains a challenge. Here, we report on attempts to control the size of crystallographic domains and lattice relaxation profile of 150-nm-thick BaTiO3 films on Si grown by molecular beam epitaxy by varying the heating and cooling rates during the film growth process while maintaining strict epitaxial and stoichiometric control. The film’s crystallographic microstructure is visualized via plan-view transmission electron microscopy to visualize the near surface lattice relaxation and crystallographic domain morphology. By carefully controlling the lattice relaxation evolution, the measured effective electro-optic response reaches values greater than 550 pm/V; it is observed that while the total electro-optic modulation of the films varies with heating/cooling rate, the effective response normalized to a-axis volume fraction does not. Strain relaxation in BaTiO₃ thin films integrated on Si affects electro-optic performance but remains poorly understood, especially in thick films. Here, the heating and cooling rates during molecular beam epitaxy growth are controlled to tune domain structure, achieving <550 pm/V effective Pockels response.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper reports 150-nm-thick epitaxial BaTiO3 films grown on Si by molecular beam epitaxy with controlled heating/cooling rates, achieving effective Pockels coefficients above 550 pm/V. Slower cooling increased the a-axis-oriented volume and lattice relaxation, but the effective electro-optic response normalized to a-axis volume fraction remained similar across films.

Key findings

  • Effective Pockels coefficients exceeded 550 pm/V: 554 ± 45 pm/V for 50 °C/min, 593 ± 29 pm/V for 10 °C/min, and 585 ± 44 pm/V for 5 °C/min (Table 2).
  • Slower cooling produced more a-axis-oriented BaTiO3 and greater relaxation, opposite to the conventional expectation for BaTiO3 on Si. The a-axis equivalent thicknesses were 104 nm for 50 °C/min, 122 nm for 10 °C/min, and 123 nm for 5 °C/min (Table 1).
  • Crystallographic domain morphology and size appeared similar for films cooled at 50 °C/min and 5 °C/min, with domains forming patches, some continuous and some around 50–100 nm in size.
  • Raw electro-optic modulation varied with a-axis equivalent thickness, but the effective response normalized to a-axis volume fraction was similar across films, suggesting the effective Pockels response is not strongly dependent on lattice relaxation or domain size after sufficient relaxation.

Methods

  • 150-nm BaTiO3 films were grown by molecular beam epitaxy on SrTiO3-buffered Si (001), with heating/cooling rates of 50, 10, and 5 °C/min; RHEED and XPS were used to confirm epitaxy and stoichiometry.
  • Structural characterization included out-of-plane and in-plane X-ray diffraction of the 004 region, plan-view STEM/HAADF imaging, precession 4D-STEM, and geometric phase analysis.
  • Electro-optic measurements used chromium contact pads, a 1550 nm laser, ±30 V DC poling, ±20 V DC and 3 Vpp AC bias, and lock-in detection to extract effective Pockels coefficients.

Limitations

  • Stated: the mechanical boundary conditions in the plan-view lamella may differ from those in the original film on substrate, so quantitative strain values may differ.
  • Stated: the exact thickness at which electrostatic boundary conditions become the dominant factor in strain relaxation was not determined.
  • Evident: the study is limited to 150-nm-thick films and three heating/cooling rates, so generality to other thicknesses or rates is not established.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/s43246-025-00908-x

Cites

Statistics

Nothing to recompute.

Claims the paper makes

0 of 28 cited sources checked · 0 supported · 0 flagged

  • Findingcitation

    The results shown by out-of-plane XRD are opposite to what has been expected in prior studies.

    “The results shown by OOP XRD are opposite to what has been expected in prior studies 20,27 .”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [20] Reynaud, M. et al. Microstructural analysis and electro-optic properties of thick epitaxial BaTiO3 films integrated on silicon (001). Phys. Rev. Mater. 6, 095201 (2022). source

      Not checked in the free run.

    • cites [27] Vaithyanathan, V. et al. c-axis oriented epitaxial BaTiO3 films on (001). Si. J. Appl. Phys. 100, 024108 (2006). source

      Not checked in the free run.

  • Findingown data

    The general trend for the out-of-plane lattice constant of the a-oriented region is that by cooling slower, the film relaxes more.

    “The general trend for the OOP lattice constant of the a-oriented region is that by cooling slower, the film relaxes more.”
    Quote in the paperSubstantial claim
  • Findingown data

    Two 90° domains are present in the top region of the films.

    “Two 90° domains are present in the top region.”
    Quote in the paperSubstantial claim
  • Findingown data

    The authors' films show the opposite trend to Li et al.: more c-oriented with fast cooling.

    “As discussed below, we observe the opposite trend in our films (more c-oriented with fast cooling)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [39] Li, W., Landis, C. M. & Demkov, A. A. Evolution of epitaxial BaTiO3 on SrTiO3-buffered Si: Phase field analysis. J. Appl. Phys. 132, 213103 (2022). source

      Not checked in the free run.

  • Findingown data

    For the film cooled at 50 °C/min, the a-axis oriented region's out-of-plane lattice constant is not fully relaxed to bulk lattice constants.

    “and the a-axis oriented region's OOP lattice constant is not fully relaxed to bulk lattice constants.”
    Quote in the paperNot a substantial claim
  • May combine two claims. 25
  • Classified as probably not a substantial claim. 13
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingnone given

    Relaxation occurs at a lower thickness for slow cooled films, while at a larger thickness for fast cooled films.

    “The relaxation occurs at a lower thickness for slow cooled films, while at a larger thickness for fast cooled films.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data
    § Enhancement of electro-optic response in BaTiO 3 films integrated on Si via heating and cooling rate control Check for updates

    The raw electro-optic modulation of each film is not identical.

    “while the raw EO modulation of each film is not identical,”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    Films cooled at 10 °C/min and 5 °C/min show a smaller region of c-axis oriented BaTiO3 than the 50 °C/min film.

    “However, the films cooled at 10 °C/ min and 5 °C/min show a smaller region of c-axis oriented BTO,”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Close to the interface the film is c-oriented, with 180° domains.

    “Close to the interface the film is c-oriented, with 180° domains.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    The dislocations appear as pairs, forming an angle of around 45° with each other.

    “Interestingly, the dislocations appear as pairs, forming an angle of around 45° with each other.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The domains manifested as patches, with some being continuous and some being about 50-100 nm in size.

    “We found that the domains manifested as patches, with some being continuous and some being ~50-100 nm in size.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The domains manifest as patches, with some being continuous and others around 50-100 nm in size.

    “The domains manifest as patches, with some being continuous and others around 50-100 nm in size.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    4D precession STEM showed that films cooled at different rates have similarly sized domains but different relaxation.

    “This compares favorably with the 4D precession STEM, which showed that films cooled at different rates have similarly sized domains but different relaxation.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The 4D STEM precession diffraction measurements are representative of the domain structure across the entire film.

  • May combine two claims.

    Findingown data

    The films showed noticeably varying XRD results, which indicate that films cooled slower have more a-axis oriented BTO versus fast cooled films, indicating more substantial relaxation.

    “The films showed noticeably varying XRD results, which indicate that films cooled slower have more a-axis oriented BTO versus fast cooled films, indicating more substantial relaxation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The films cooled at 5 °C/min and 10 °C/min have almost the same thickness of a-axis BTO while the film cooled at 50 °C/min has noticeably less, and have comparable raw modulation even though their relaxation is different.

    “The films cooled at 5 °C/min and 10 °C/min have almost the same thickness of a-axis BTO while the film cooled at 50 °C/min has noticeably less, and have comparable raw modulation even though their relaxation is different.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The effective Pockels response for these BTO films is very large and higher than other recently reported effective coefficients, which max out at about 525 pm/V.

    “First of all, we note that the effective Pockels response for these films is very large and even higher than other recently reported effective coefficients which max out at ~525 pm/V 4,23,45 , which we think is due to extensive relaxation while maintaining a high level of epitaxy when compared to our previous work 20 ].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [4] Eltes, F. et al. An integrated optical modulator operating at cryogenic temperatures. Nat. Mater. 19, 1164–1168 (2020). source

      Not checked in the free run.

    • cites [23] Abel, S. et al. A strong electro-optically active lead-free ferroelectric integrated on silicon. Nat. Commun. 4, 1671 (2013). source

      Not checked in the free run.

    • cites [45] Picavet, E. et al. Integration of solution processed BaTiO3 thin films with high pockels coefficient on photonic platforms. Adv. Funct. Mater. 34, 2403024 (2024). source

      Not checked in the free run.

  • May combine two claims.

    Findingnone given

    The raw modulation of the films is similar with films that have similar a-thicknesses of BTO, while the effective response is similar between all of the films.

    “The raw modulation of the films is similar with films that have similar a-thicknesses of BTO, while the effective response is similar between all of the films.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationown data

    Some other effect should be considered for thick BaTiO3 films grown on Si.

    “which leads us to believe that there is some other effect that should considered for thick BTO films grown on Si.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    One possible explanation for the opposite trend is that electromechanical boundary conditions begin to have a stronger effect on the cubic-to-tetragonal transition when BaTiO3 films surpass a certain thickness.

    “Because these films are sufficiently thicker than traditional BTO films grown by MBE 20,27,30 , one possible explanation is that the electromechanical boundary conditions begin to have a stronger effect on the cubic-to-tetragonal transition when BTO films surpass a certain thickness.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [20] Reynaud, M. et al. Microstructural analysis and electro-optic properties of thick epitaxial BaTiO3 films integrated on silicon (001). Phys. Rev. Mater. 6, 095201 (2022). source

      Not checked in the free run.

    • cites [27] Vaithyanathan, V. et al. c-axis oriented epitaxial BaTiO3 films on (001). Si. J. Appl. Phys. 100, 024108 (2006). source

      Not checked in the free run.

    • cites [30] Dubourdieu, C. et al. Switching of ferroelectric polarization in epitaxial BaTiO3 films on silicon without a conducting bottom electrode. Nat. Nanotechnol. 8, 748 (2013). source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In prior work, BaTiO3 films grown by MBE with ~110 nm thickness cooled at 50 °C/min show an almost c-axis oriented out-of-plane lattice constant while still showing a large electro-optic response.

    “in our prior work we have seen that BTO films grown by MBE with ~110 nm thickness cooled at 50 °C/min show an almost c-axis oriented OOP lattice constant, while still showing a large electro-optic response 20 .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] Reynaud, M. et al. Microstructural analysis and electro-optic properties of thick epitaxial BaTiO3 films integrated on silicon (001). Phys. Rev. Mater. 6, 095201 (2022). source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    When grown on SrTiO3-buffered Si, BaTiO3 first assumes the c-axis orientation before gradually transitioning into the a-axis orientation.

    “When grown on STO-buffered Si, BTO will first assume the c-axis orientation (long axis perpendicular to the substrate) before gradually transitioning into the a-axis orientation (long axis parallel to the substrate).”
    Quote in the paperSubstantial claim0 of 4 sources checked
    • cites [20] Reynaud, M. et al. Microstructural analysis and electro-optic properties of thick epitaxial BaTiO3 films integrated on silicon (001). Phys. Rev. Mater. 6, 095201 (2022). source

      Not checked in the free run.

    • cites [25] Hsu, M.-H. M. et al. Controlled orientation of molecular-beam-epitaxial BaTiO3 on Si (001) using thickness engineering of BaTiO3 and SrTiO3 buffer layers. Appl. Phys. Express 10, 065501 (2017). source

      Not checked in the free run.

    • cites [27] Vaithyanathan, V. et al. c-axis oriented epitaxial BaTiO3 films on (001). Si. J. Appl. Phys. 100, 024108 (2006). source

      Not checked in the free run.

    • cites [30] Dubourdieu, C. et al. Switching of ferroelectric polarization in epitaxial BaTiO3 films on silicon without a conducting bottom electrode. Nat. Nanotechnol. 8, 748 (2013). source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    The large thermal expansion coefficient mismatch forces the film to be a-axis oriented, while lattice constant differences prefer a c-axis orientation.

    “The large thermal expansion coefficient mismatch forces the film to be a-axis oriented, while the lattice constant differences prefer a c-axis orientation.”
    • Also stated in: § Crystallographic analysis · hedged
      “As stated previously, the conventional thought for BTO on Si is that by cooling faster, the film will be forced into the a-axis orientation because of thermal expansion mismatch 27 .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [27] Vaithyanathan, V. et al. c-axis oriented epitaxial BaTiO3 films on (001). Si. J. Appl. Phys. 100, 024108 (2006). source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    The commonly accepted explanation for BaTiO3 reorientation is that two main contributions to strain in the film are thermal expansion mismatch between the layers and lattice constant difference between the layers.

    “The commonly accepted explanation for such reorientation is that there are two main contributions to strain in the BTO film, namely the thermal expansion mismatch between the different layers, along with the lattice constant difference between the layers 27 .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [27] Vaithyanathan, V. et al. c-axis oriented epitaxial BaTiO3 films on (001). Si. J. Appl. Phys. 100, 024108 (2006). source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The films start out moderately compressed at the growth temperature, undergo the paraelectric-to-ferroelectric transition at a temperature much higher than bulk stress-free BaTiO3 (~125 °C), and maintain a large in-plane polarized region close to the surface.

    “The films start out moderately compressed at the growth temperature, undergoes the paraelectric-to-ferroelectric transition at temperature much higher than bulk stress-free BTO (~125 °C), and maintains a large in-plane polarized region close to the surface.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationcitation

    Instead of thermal expansion mismatch and initial compressive strain being the primary cause for strain relaxation for films cooled slowly, electrostatic energy build-up causes a preference for the film to be polarized in-plane near the surface versus out-of-plane, which causes the film to fall in-plane more easily.

    “This would mean that instead of thermal expansion mismatch and initial compressive strain on the BTO being the primary cause for strain relaxation for films cooled slowly, the electrostatic energy build-up causes a preference for the film to be polarized in-plane near the surface versus out-of-plane, which causes the film to fall in-plane more easily 39,41 .”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [39] Li, W., Landis, C. M. & Demkov, A. A. Evolution of epitaxial BaTiO3 on SrTiO3-buffered Si: Phase field analysis. J. Appl. Phys. 132, 213103 (2022). source

      Not checked in the free run.

    • cites [41] Lines, M. E. & Glass, A. M. Principles and applications of ferroelectrics and related materials (Oxford University Press, 2001). source

      Not checked in the free run.

  • May combine two claims.

    Study design and conductown data

    The ratio of x-spacing to y-spacing can be used to map the orientation of orthogonal a-domains, as confirmed by atomic-scale polarization analysis and nano-scale GPA analysis.

    “The ratio of x-spacing to y-spacing can be used to map the orientation of the orthogonal adomains, as confirmed by our atomic-scale polarization analysis (Supplementary Note 3, Supplementary Fig. S1) as well as nano-scale GPA analysis (Supplementary Note 3, Supplementary Fig. S2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The crystallographic domain size is more dependent on defect density, which is similar between the films.

    “The film's orientation was studied using 4D STEM precession diffraction, and we found that the crystallographic domain size does not vary strongly with different cooling rates, and is more dependent on defect density which is similar between the films.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The 4D STEM precession diffraction measurements are representative of the domain structure across the entire film.

  • May combine two claims.

    Study design and conductown data

    To ensure that results are due to varying the heating and cooling rate and not due to film quality, the authors closely monitored RHEED images to ensure no phase segregation was seen due to stoichiometry deviating from a 1:1 Ba:Ti ratio and used XPS to confirm stoichiometry at 50, 100 and 150 nm thicknesses for BTO.

    “To ensure that any results are due to varying the heating and cooling rate and not due to film quality, we closely monitored the RHEED images of the films to ensure that no phase segregation was seen due to the stoichiometry deviating away from a 1:1 Ba:Ti ratio and used XPS to confirm the stoichiometry at 50, 100 and 150 nm thicknesses for BTO.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The raw modulation is not dependent on the domain size, only on the thickness of a-axis oriented BTO.

    “This implies that the raw modulation is not dependent on the domain size, only on the thickness of a-axis oriented BTO.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The 4D STEM precession diffraction measurements are representative of the domain structure across the entire film.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Study design and conductnone given

    The mechanical boundary conditions in a plan-view lamella may not be the same as in the original film on substrate, and the quantitative strain observed may be different.

    “It should be noted that the mechanical boundary conditions in a plan-view lamella may not be the same as in the original film on substrate and it is likely that the quantitative strain observed may be different.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

    Interpretationnone given

    The opposite result may be due to the electro-static boundary conditions having a more noticeable effect in the strain relaxation dynamics.

    “We think this may be due to the electro-static boundary conditions having a more noticeable effect in the strain relaxation dynamics.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    Both positive and negative DC biases were measured to account for possible variations in the electro-optic signal when applying fields in opposite directions as a result of possible polarization pinning.

    “Both positive and negative DC biases were measured to account for possible variations in the EO signal when applying the fields in opposite directions as a result of possible polarization pinning 30 .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [30] Dubourdieu, C. et al. Switching of ferroelectric polarization in epitaxial BaTiO3 films on silicon without a conducting bottom electrode. Nat. Nanotechnol. 8, 748 (2013). source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    The electro-optic response of the films is very large, likely due to the sufficient relaxation of the films.

    “The electro-optic response of the films is very large, likely due to the sufficient relaxation of the films.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    RHEED images and XPS results confirm high quality stoichiometry and epitaxy of the films.

    “RHEED images and XPS results of the film confirming high quality stoichiometry and epitaxy can be found in Supplementary Note 1.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The effective Pockels response of the films is almost the same even with differing lattice constants and thus relaxation, and after sufficient a-to-c relaxation has occurred the films will give similar electro-optic responses.

    “This implies the effective Pockels response of the films is almost the same even with differing lattice constants and thus relaxation, and that after sufficient a-to c-relaxation has occurred the films will give similar electro-optic responses.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The a-axis equivalent thickness δ/2 adequately accounts for the contribution of a-axis oriented BTO to the measured raw modulation.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Each data point is a result of at least 30 measurements.

    “Each data point is a result of at least 30 measurements.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The Pockels response is either not dependent or not strongly dependent on the relaxation after a sufficient thickness.

    “showing the Pockels response is either not dependent or not strongly dependent on the relaxation after a sufficient thickness”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The effective Pockels response is either not dependent or only weakly dependent on the relaxation of the BTO beyond a certain point for sufficiently thick films.

    “This indicates that the effective Pockels response is either not dependent or only weakly dependent on the relaxation of the BTO beyond a certain point for sufficiently thick films 24 .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [24] Kormondy, K. J. et al. Microstructure and ferroelectricity of BaTiO3 thin films on Si for integrated photonics. Nanotechnology 28, 075706 (2017). source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    The BaTiO3 films were poled using ±30 V DC (3×10^6 V/m) bias for 2 min, well beyond the coercive field seen for other thick BaTiO3 films.

    “To perform the measurements, the BTO is first poled using a ±30 V DC (3 ×10 6 V/m) bias for 2 min, well beyond the coercive field seen for other thick BTO films 23 .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [23] Abel, S. et al. A strong electro-optically active lead-free ferroelectric integrated on silicon. Nat. Commun. 4, 1671 (2013). source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Electro-optic modulation has been shown to depend on input angle, and θi = 0° is the angular input corresponding to maximum electro-optic modulation for 4 mm BaTiO3 barring misalignments.

    “EO modulation has been shown to depend on the input angle, and this angle has been shown to be the angular input corresponding to maximum electro-optic modulation for 4 mm BTO barring any misalignments of the optical setup or sample mounting 23,44 .”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [23] Abel, S. et al. A strong electro-optically active lead-free ferroelectric integrated on silicon. Nat. Commun. 4, 1671 (2013). source

      Not checked in the free run.

    • cites [44] Posadas, A. B. et al. Thick BaTiO3 epitaxial films integrated on Si by RF sputtering for electro-optic modulators in Si photonics. ACS Appl. Mater. Interfaces 13, 51230–51244 (2021). source

      Not checked in the free run.

35 of 35

  • The paper relies on this without support.

    Control of the crystallographic domain structure of high-quality epitaxial BaTiO3 films remains a challenge.

    “However, control of the crystallographic domain structure of high-quality epitaxial BaTiO3 films still remains a challenge.”

  • The paper relies on this without support.

    Currently, there have not been any thorough studies relating the heating and cooling rates during growth to the crystallographic and electro-optic properties of BaTiO3 films.

    “Currently, however, there have not been any thorough studies relating the heating and cooling rates during the growth of these films to the crystallographic and EO properties of the films.”

  • The paper relies on this without support.

    The a-axis equivalent thickness δ/2 adequately accounts for the contribution of a-axis oriented BTO to the measured raw modulation.

    “When the raw modulation is converted to effective Pockels coefficients after accounting for a-axis equivalent thickness, the values are much closer.”

  • The paper relies on this without support.

    The 4D STEM precession diffraction measurements are representative of the domain structure across the entire film.

    “This compares favorably with the 4D precession STEM, which showed that films cooled at different rates have similarly sized domains but different relaxation.”
4 of 4

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • BaTiO3 has a transparency window from 460 to 6300 nm, high refractive index, and can be epitaxially integrated on silicon-on-insulator substrates.

    “Similarly to LN, due to its transparency window that is wide, from 460 to 6300 nm, BTO becomes another candidate for communication technology. Waveguides are a possible application of this ferroelectric material, due to its high refractive index value as well as its epitaxial integration on siliconon-insulator substrates [204-208].”

    From Metal Oxide Thin Films for Advanced Photonic Applications (2026) · cites this paper as [204]

    The introduction describes BaTiO3 waveguides and says a SrTiO3 buffer allows BaTiO3 to grow epitaxially on silicon (page unavailable). It does not give a 460–6300 nm transparency window or characterize BaTiO3 as having a high refractive index. Although the References list a study of modulators on silicon-on-insulator substrates, this paper reports epitaxial films on Si (001), not epitaxial integration on silicon-on-insulator. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • BaTiO3 has a Pockels coefficient larger than 1000 pm/V, the highest compared to other stoichiometric complex oxides.

    “Barium titanate (BaTiO3 or BaO × TiO2 or BT) is a lead-free ferroelectric material, which in recent years has had a growing range of applications, especially in the photonic field [180,202], and more specifically in nonlinear optics due to its Pockels coefficient being larger than 1000 pm/V [203], the highest in comparison to other stoichiometric complex oxides [204,205].”

    From Metal Oxide Thin Films for Advanced Photonic Applications (2026) · cites this paper as [204]

    The introduction describes BaTiO3 as having an exceptionally large electro-optic response compared with LiNbO3, but cites a reported tensor component of about 923 pm/V, not more than 1000 pm/V. The paper reports effective coefficients above 550 pm/V for its own films and does not establish that BaTiO3 has the highest coefficient among stoichiometric complex oxides (introduction; Electro-optic measurements; page numbers unavailable). (LLM, conf=0.84)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Shear strain map is assigned to two different figures

    Minor

    The discussion locates the GPA shear strain map in Fig. 4g, while the figure caption identifies it as Fig. 3g. The supplied Fig. 4 caption lists only panels a-d.

  • Relaxation direction reverses within the paper

    Minor

    The text describes thick films as relaxing from c-axis to a-axis orientation, but later calls the process a-to-c relaxation.

2 of 2

The citation lists haven’t been fetched yet

References 43 · Cited by 14

Research works printed but not linked: 3

  1. Speck, J. S. & Pompe, W. Domain configurations due to multiple misfit relaxation mechanisms in epitaxial ferroelectric thin films. I. Theory J. Appl. Phys. 76, 466–476 (1994).
  2. Yariv, A. & Yeh, P. Optical waves in crystals Ch. 7 (Wiley Interscience, 1984).
  3. Reynaud, M. Orientation and polarization control of BaTiO₃ films for applications in Si-integrated photonics. PhD thesis, University of Texas at Austin (2023).

Authors
Reynaud, M., Waqar, M., Du, C., Posadas, A. B., Pan, X., & Demkov, A. A.
Affiliations
  • The University of Texas at Austin (US)
  • University of California, Irvine (US)
Corresponding author
Demkov, Alexander A.
ORCID
Venue
Communications Materials
Publisher
Springer Science and Business Media LLC
Published
2025-08-06
Volume
6
Issue
1
ISSN
2662-4443 (ISSN-L)
DOI
10.1038/s43246-025-00908-x
OpenAlex
W4413011640
Semantic Scholar
281351f87130d29f443add38bbbb0fd84e2324fe
Cited by
14
References
43
Citations by year
2026: 12 · 2025: 2
FWCI
2.98
Type
journal article
Language
en
Open access
Licence
Locations
  • Communications Materials (publishedVersion, cc-by-nc-nd)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • Multidisciplinary University Research Initiative (FA9550-22-1-0307)
  • Air Force Office of Scientific Research (FA9550-, FA9550-22-1-0307, FA9550-18-1-0053.)
Topics
  • Physical Sciences › Materials Science › Materials Chemistry › Ferroelectric and Piezoelectric Materials
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Photorefractive and Nonlinear Optics
  • Physical Sciences › Materials Science › Electronic, Optical and Magnetic Materials › Multiferroics and related materials
Keywords
BaTiO3 thin films, electro-optic response, Pockels effect, lattice relaxation, epitaxial growth, strain relaxation, molecular beam epitaxy, domain size control

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