Enhanced production of active species and NH_3 using non-equilibrium ferroelectric barrier discharge

Domain: physics
Published: 2025-12-13
Editorial outcome: major_revision

Abstract
Non-equilibrium plasma-assisted ammonia synthesis is investigated through enhanced active species production with ferroelectric discharge. Time-resolved in-situ diagnostics of femtosecond two-photon absorption laser-induced fluorescence, coherent anti-Stokes Raman scattering, and laser absorption spectroscopy, as well as optical emission spectroscopy, were conducted to probe the key intermediate species, such as H and N radicals as well as N2 (ν), ions, and NH3 to achieve better understanding of non-equilibrium energy transfer and ammonia formation. The results reveal that ferroelectric discharge improved ammonia yield by four times. Results also show that ferroelectrics not only enhanced ions (N2+) production, radicals (N, H) number density, but also increased the N2 vibrational temperature. Further plasma modeling identified the couplings between elevated radical and ion production and enhanced vibrational excitation reactions, e.g., N+H2 (ν)→NH+H, N2 (ν)+H→NNH, N2++H2→H+N2H+, and N2H++e→NH+N, facilitated by ferroelectric discharge. These findings provide critical insight into the mechanism of ferroelectric plasma catalysis and highlight their potential in advancing energy-efficient chemical synthesis.

Introduction
Non-equilibrium plasma catalysis powered by renewable electricity is emerging as a promising strategy for green and efficient manufacturing by enabling new reaction pathways compared to conventional high-temperature equilibrium processes. Plasma technologies have demonstrated great potential in fields such as catalysis1, material synthesis2, combustion3,4, etc. Non-equilibrium plasmas produce excited species, radicals, as well as space and surface charges, which lower kinetic barriers and facilitate chemical reactions across gas-liquid-solid interfaces—often at reduced temperatures5. Despite its advantages, low-temperature plasma manufacturing faces several challenges. Firstly, the complexity of plasma chemistry, characterized by numerous types of reactive species and competing reaction pathways, hinders the kinetic understanding of the mechanism of plasma-assisted chemical synthesis. Additionally, the conversion efficiency of low-temperature plasma processes remains significantly lower than that of the conventional high-temperature methods. For example, plasma-assisted catalysis produces only 15-30g of NH3 per kWh of energy input6, compared to 500 g-NH3/kWh for the Haber-Bosch process7. Therefore, a new method to control plasma generation and chemistry is needed.

In terms of plasma chemistry, vibrationally excited species, radicals, and ions are all believed to play critical roles in plasma-assisted ammonia synthesis, as supported by experimental and computational studies. Vibrationally excited nitrogen, N2 (ν), is expected to enhance the dissociative adsorption rate on catalyst surfaces, thereby generating more adsorbed nitrogen species compared to ground-state N2 8,9. Adamovich et al. further demonstrated that applying a sub-breakdown radio frequency (RF) waveform alongside nanosecond discharges increased the vibrational temperature of N2, correlating with higher ammonia yields10. Complementary to this, Koel and Sundaresan’s parametric analysis showed that copious amounts of N2 (ν) lead to markedly higher dissociative adsorption rates on catalytic metal surfaces11. On the other hand, although N and H radicals are present in relatively small quantities due to their high formation energy, their high reactivity enables them to directly participate in surface reactions, enhancing overall reaction rates and unlocking alternative pathways8. Bruggeman and Bhan12 highlighted the importance of radicals by demonstrating that surface reactions enable higher and more selective conversion to NH3 than gas-phase reactions alone and H is required to produce NH3. On the ionic side, Carrasco et al13. mapped the dominant ion-molecule channels in low-pressure H2/N2 plasmas and showed that reactions initiated by N2+ and H2+ (formed rapidly from H2+) efficiently supply NH/NH2 precursors that accelerate NH3 formation. However, simultaneous in-situ diagnostics of H, N, and N2 (ν) in non-equilibrium plasma synthesis of ammonia are rarely conducted.

To promote efficient plasma-surface interaction and control plasma chemistry, recent efforts have focused on integrating ferroelectric materials, which possess spontaneous electric polarization and strong surface charge production. Studies on ferroelectric packed-bed plasma-catalytic systems for ammonia synthesis have demonstrated both higher efficiency and improved yields14,15. However, the fundamental properties and kinetics of ferroelectric barrier discharges (FBD) remain insufficiently explored. Existing investigations have primarily focused on the electrical behavior16,17 and spatial discharge patterns18 within FBD plasmas, leaving a knowledge gap in understanding the connections between ferroelectric polarization and plasma chemistry. Gómez—Ramírez et al19. explored how ammonia synthesis efficiency and certain electronically excited plasma species—mainly N2*, N*, NH* and N2+* (* denote electronically excited states)—respond to applied voltage and frequency, electrode gap, and the type of ferroelectric material. However, due to the constraint of the packed bed geometry, their analysis primarily targeted the overall process performance without resolving the transient kinetics of radicals or vibrationally excited species. Notably, our previous study has reported that ferroelectric polarization-induced surface charges significantly enhance the electric field during N2 gas breakdown and prolong the afterglow period20, suggesting the potential for further improving plasma-assisted chemical manufacturing. However, although ferroelectric barrier discharges’ properties are significantly different from those of normal DBD, critical investigations into time-sensitive plasma chemistry, specifically regarding radicals and vibrational excited species for ammonia synthesis, are still lacking. These open questions continue to hinder the development of FBD plasma manufacturing.

This work advances the fundamental understanding of N2/H2 ferroelectric barrier discharges by using advanced time-resolved laser diagnostics to capture the instantaneous evolution of plasma chemistry of radicals and vibrationally excited states. Ferroelectric polarization and surface charge behavior are directly correlated with the production dynamics of key active species, including ground-state radicals, ions and vibrationally excited molecules. It is demonstrated that N2/H2 FBDs generate significantly higher surface charge densities—on the order of 10-1 µC cm-2—exceeding those of conventional dielectric barrier discharges by at least an order of magnitude. To examine the ion production in FBD and Al2O3 DBD, we performed optical emission spectroscopy (OES) measurements. To quantify radical productions, vibrational excitations and ammonia synthesis, we employed time-resolved in-situ diagnostics: femtosecond two-photon absorption laser-induced fluorescence (fs-TALIF) for N and H radicals, coherent anti-Stokes Raman scattering (CARS) for N2 (ν), and laser absorption spectroscopy (LAS) for NH3. It is found that the production of NH3 as well as N and H radicals and ions (N2+*), is significantly promoted. The high electric field induced by the high surface charge from the ferroelectrics promotes both N and H radical peak number densities by at least a factor of two. Additionally, results also show that the vibrational excitation of N2 is enhanced in FBD, and it shows the vibrational temperatures of 1595 K and 885 K for pure N2 and N2/H2 mixtures in FBD, while no detectable bands of ν≥1 could be seen in Al2O3 DBD. Parametric investigations of active species generation and NH3 production in FBD and Al2O3 DBD with different flow rates and N2/H2 ratios further confirm the generality of these trends. Further plasma kinetic modeling highlights the critical role of coupling reactions between radicals and vibrationally excited species—such as N+H2 (ν)→NH+H, N2 (ν)+H→NNH—in the reaction network. Ion chemistry featuring N2+, H2+ and N2H+ could also be a major contributor, with its prominence increasing at higher E/N as ionic pathways become more active. These findings reinforce the conclusion that the synergy among elevated radical and ion production, enhanced vibrational excitation, and potential plasma-surface interactions mediated by ferroelectric polarization fundamentally alters plasma kinetics and facilitates low-temperature plasma-driven chemical reactions. Our study delves into the plasma chemistry of ferroelectric barrier discharge, providing a deeper understanding of its underlying science, and facilitating its application in plasma-assisted processes.

Results
Surface charge generation using a lead zirconate titanate (PZT) barrier
As illustrated in Fig. 1a, a ferroelectric barrier discharge is established by incorporating a lead zirconate titanate (PZT) layer to induce rapid electric polarization and generate a large surface charge, therefore enabling control over plasma properties and manipulation of plasma chemistry. For comparison, a conventional dielectric barrier discharge is also constructed by replacing the PZT layer with an alumina (Al2O3) layer of identical dimensions. In both FBD and Al2O3 DBD configurations, the plasma is generated in a plate-to-plate arrangement between two parallel electrodes. Further details regarding the plasma cell design and operational conditions are provided in the Methods section and in our previous study20.

The ferroelectric lead zirconate titanate used in this study is a ceramic perovskite material that exhibits a tetragonal P4mm crystal structure (below its Curie temperature). This asymmetric crystal structure results in the displacements of positive and negative charge centers within the unit cell and equips PZT with inherent spontaneous polarization. In contrast, alumina (α-Al2O3) employed in the dielectric barrier discharge possesses a hexagonal corundum structure with the space group R3¯c (no. 167), leaving no spontaneous polarization. The X-ray diffraction patterns of the lead zirconate titanate plate and alumina plate used in this work confirm the high purity and crystallinity of the materials, as shown in Fig. 1(b) and (c). To ensure optimal ferroelectric performance in the FBD configuration, the PZT plate is supplied in a fully poled and application-ready state as explained in the Methods section.

To enable in-situ quantification and comparison of surface charge generation in ferroelectric barrier discharge and dielectric barrier discharge, we adopt the Sawyer-Tower method21. Further methodological details are provided in the Supporting Information Fig. S1 and in our previous work20. As illustrated in Fig. 1d–f, the ferroelectric PZT barrier accumulates significantly more surface charge than the dielectric alumina barrier across different gas mixtures. In pure N2 (Fig. 1d), the PZT induces a surface charge of 0.09 μC cm−2, whereas the Al2O3 DBD configuration yields a charge of two orders of magnitude lower, at ~10–4 μC cm−2. When 75% H2 is introduced into the gas mixture while maintaining constant pressure and total flow (Fig. 1e), the peak surface charge in the FBD increases to 0.15 μC cm−2. This enhancement is primarily attributed to the rise in electron temperature due to H2 addition22, which promotes the bombardment of energetic particles on the ferroelectric surface and consequently enhances secondary electron emission. The resulting elevated electron energy and density in FBD increase the likelihood of electron-molecule collisions, thereby generating more excited species (both electronic and vibrational) and ions compared to Al2O3 DBD. Additionally, differences in secondary electron emission can be influenced by the materials’ work functions: PZT has a slightly lower work function than alumina (4.5 eV vs. 4.7 eV)23,24. However, when switching to pure H2 (Fig. 1f), the peak surface charge drops to ~0.07 μC cm-2. This reduction is likely due to the non-monotonic behavior of secondary electron yield, which can decrease beyond a certain incident particle energy threshold25. In Al2O3 DBD, the peak surface charge in pure H2 (0.03 μC cm-2), as shown in Fig. 1(f), is noticeably higher than in pure N2 or N2/H2 mixture. This can be attributed to the distinct plasma properties of H2: its lower breakdown voltage and higher ion mobility facilitate more conductive discharge channels, which increase the displacement current and the total transferred charge per cycle26–28.

Furthermore, as shown in Fig. 1d–f and Supporting Information Figure S2, the breakdown voltage of the ferroelectric barrier discharge increases with higher N2 concentrations in the gas mixture, in accordance with Paschen’s law29. Notably, when H2 is present, the voltage-charge loop exhibits distortions at both the left and right turning points of the curve. These irregularities are attributed to a voltage drop at the moment of gas breakdown, as evident in Supporting Information Figure S2. This voltage drop arises from an overshoot in the electric field and current, as well as the initiation of micro-discharges during breakdown events30.

Intensified ionization: increased N2+*/N2* ratio in ferroelectric barrier discharge
In plasma-catalysis research, gas-phase ion chemistry plays a crucial role in reaction processes, not only by directly changing plasma properties but also via radical and intermediate species production. To compare the ion concentrations in FBD and Al2O3 DBD, OES measurements are performed, as shown in Fig. 2. In Fig. 2(a), the spectra display major nitrogen-related emission peaks corresponding to the second positive band N2 (C3Πu - B3Πg) and the first negative band N2+(B2Σu+ - X2Σg)31,32. In Fig. 2(b), the main observed features include the Balmer-α and Balmer-β atomic hydrogen lines33,34.

The results show that under identical gas compositions, the FBD consistently produces stronger emissions than Al2O3 DBD, including emissions from excited molecules and radicals, but more importantly from different ions. This enhancement is likely due to the higher local electric field and stronger electron acceleration capability in FBD, which leads to higher average electron energies and, consequently, increased electron-impact ionization cross-sections and frequencies. However, an interesting phenomenon was observed: in N2/H2 mixtures, the intensity ratio of N2+* to excited N2* is higher compared to pure N2. To illustrate this more clearly, the peak areas are integrated, as shown in Table 1. The numerical results are consistent with the spectral trends: FBD always gives higher intensities than Al2O3 DBD, and the addition of H2 markedly increases the N2+*/N2* ratio, with the effect being more pronounced in FBD. As shown in Supporting Information Figure S3 and Figure S4, even with different total flow rates (50 sccm and 100 sccm) and N2/H2 ratios (0%, 25%, 50%, 75% and 100% N2), the conclusion of enhanced emissions in FBD and increased N2+*/N2* with H2 still holds. This may be attributed to changes in the electron energy distribution function upon H2 addition35, which increases the fraction of high-energy electrons and thus enhances N2 ionization, while the presence of H2 competes for excitation of N2, reducing the relative population of N2* and leading to a higher N2+*/N2* ratio.

Enhanced production of N and H radicals in ferroelectric barrier discharge
Interest in understanding the role of radicals in plasma-assisted ammonia synthesis continues to increase36,37. Figure 3a presents the absolute number densities of N radicals measured by fs-TALIF across different gas compositions in both FBD and Al2O3 DBD plasmas over a single voltage cycle. As shown in Fig. 3a, the time when the peak N radical densities occur coincides with the time at which the applied voltage drops, indicating that most N radicals are generated during gas breakdown. This phenomenon can be attributed to the overshoot of the electric field of FBD at breakdown, which provides sufficient energy for electron-impact dissociation of N2 molecules20. Given that the electric field in FBD is substantially higher than in Al2O3 DBD20, it is expected that the N radical densities in FBD are significantly enhanced compared to Al2O3 DBD. In pure N2, the peak N number density in FBD reaches 1.2×1016 cm-3, nearly double that of Al2O3 DBD (6.8×1015 cm-3). In N2/H2 mixtures, this difference becomes even more pronounced, with FBD exhibiting a peak value of 1.1×1016 cm-3, which is an order of magnitude higher than that of Al2O3 DBD (1.4×1015 cm-3). Moreover, the addition of H2 affects the two discharges differently: in FBD, the N radical peak density remains relatively unchanged, whereas in Al2O3 DBD, it drops significantly. This difference could be attributed to two possible mechanisms: (i) electron-impact dissociation of N2: due to the strong electric field induced by the ferroelectrics in different gas mixtures, the electron number density in FBD could remain high. While in Al2O3 DBD the electric field and electron number densities are lower and a portion of the electron energy could be diverted to dissociation of H2 (e+H2→e+H+H) rather than generating N radicals which require higher energy thresholds38, or vibrational channels such as H2+N2(ν)→H2(ν)+N2 39. (ii) additional ion-mediated pathways involving hydrogen species in FBD (will be discussed further in kinetics modelling in the last): in FBD, the sustained high E/N drives strong ionization, yielding abundant N2+, H2+ and their protonated products (e.g., N2H+). Consequently, with H2 added, N radicals are also supplied by ion-mediated pathways, most notably dissociative recombination (NH2++e→NH+N), so the net N production remains relatively stable to H2 addition. In contrast, in the Al2O3 DBD, the lower E/N and electron density reduce both ionization and ion-molecule reaction rate, leaving a negligible role of ions on the N production.

Figure 3b shows the absolute number densities of H radicals in FBD and Al2O3 DBD plasmas under various gas compositions. Similar to the trend observed for N radicals, the generation of H radicals in FBD is significantly enhanced due to the higher electric field. In pure H2, the peak H radical density in FBD reaches 8.0×1016 cm−3, over six times greater than that in Al2O3 DBD (1.2×1016 cm−3). In N2/H2 mixtures, the FBD still maintains a notable advantage, with a peak value of 2.1×1017 cm−3, nearly double that of Al2O3 DBD (1.2×1017 cm−3). Interestingly, in both FBD and Al2O3 DBD, the H radical number density counterintuitively increases upon the moderate addition of N2 to H2. This unexpected behavior may be explained by additional H production pathways facilitated by nitrogen39, such as H2(ν)+N→NH+H, and H2+N2(*)→N2+H+H, where vibrationally and electronically excited species, as well as direct electron collision in an enhanced electric field contribute to enhanced hydrogen dissociation. In addition, in FBD, ion chemistry could provide complementary sources of H. Charge transfer (N2++H2→N2+H2+) builds the H2+ pool; subsequent reactions directly and indirectly produce H radical via H2++H2→H3++H, e+H3+→H+H2, and e+H3+→H+H+H (or H2+H). Recombination reaction of N2H+ with an electron also yields H. Because these ion-mediated pathways scale with ionization, they are far more prominent in the FBD than in the Al2O3 DBD and, together with the excited-species routes, rationalize both the higher H densities in FBD and the counterintuitive rise of H upon introducing N2. Therefore, in pure H2, the steady-state H radical density in Al2O3 DBD remains relatively low, despite the larger Q-Ucell figure area observed in Fig. 1f, without N2 to provide additional excitation channels or ionic pathways for H production.

As a complementary analysis, Fig. 3c, d present the time-averaged N and H radical number densities, respectively, obtained by integrating the transient curves in Fig. 3a, b over one voltage cycle and dividing by the cycle duration. In the N2/H2 mixture, the time-averaged nN in FBD (2.8×1015 cm−3) exceeds that in Al2O3 DBD (7.1×1013 cm−3) by over two orders of magnitude, while the average nH is almost two times higher (7.4×1016 cm−3 vs. 3.8×1016 cm−3). Importantly, the trends observed in these time-averaged values are consistent with those in the instantaneous profiles of Fig. 3a, b, reaffirming that both gas composition and discharge configuration have a strong and distinct influence on radical generation. Lastly, peak number densities of N and H radicals were measured across various N2/H2 ratios and total flow rates, as shown in Supporting Information Figure S5. FBD consistently yields more N and H than the Al2O3 DBD under all compositions and flow rates examined. The qualitative dependence on gas composition mirrors the trends discussed above and remains similar across different flow conditions. The only exception arises at very N2-rich mixtures (75% N2), where the H peak decreases, likely because reactive flux is diverted into N-containing pathways, and low availability of H2.

Enhanced production of vibrationally excited N2 in ferroelectric barrier discharge
Besides radicals such as N and H, vibrationally excited N2 has been attracting attention not only from its strong coupling with radical production, but also from its role in energy transfers in plasma-catalytic synthesis of NH3. The presence of vibrationally excited N2 can significantly influence key reaction pathways and enhance overall reaction efficiency. Therefore, quantitative measurements of vibrationally excited N2 temperatures are necessary for key reaction mechanisms and kinetic model validations in plasma-assisted ammonia synthesis.

With advances in laser sources and sensitive detectors, a wide range of laser diagnostics can now quantify vibrational temperatures in plasmas, including spontaneous Raman scattering40, mid-IR laser absorption spectroscopy41, and CARS42. Of these methods, CARS stands out as a powerful technique for plasma diagnostics, owing to its high spatial and temporal resolution. In addition, the coherent signal is less susceptible to plasma emission and improves the signal-to-noise ratio. These features make CARS particularly well-suited for in-situ vibrational and rotational temperatures measurements in plasmas.

To quantitatively measure the vibrational excitation of N2, we utilize a 3-beam fs/ps coherent anti-Stokes Raman scattering (CARS) system for vibrational and rotational temperature measurements43. Figure 4a shows the vibrational CARS spectra of N2 in both Al2O3 DBD and FBD plasmas under pure N2 and 25% N2/75% H2 gas mixtures. The central spectra represent averages over a complete applied voltage cycle (50 μs), while the time-resolved color-filled spectra on the left and right illustrate the temporal evolution of vibrational excitation. In pure N2 FBD, vibrational bands up to ν=2 are clearly observed, and the spectral profile remains relatively stable throughout the voltage cycle, suggesting consistent vibrational energy distribution. Upon the introduction of H2, the intensity of the N2 hot bands decreases, and a distinct temporal window (12-20 μs) emerges in which the population of vibrationally excited N2 (ν) drops significantly. This low vibrational temperature time window coincides with the peak H radical number densities observed in the 25% N2/75% H2 FBD case (as shown in Fig. 3a), implying that there is a strong energy transfer between vibrational N2 (ν) and H2 during this period, thereby reducing vibrational excitation of N2 molecules. In contrast, vibrational N2 (ν) levels of ν≥1 are barely detectable in Al2O3 DBD under both gas compositions, indicating that the population of vibrationally excited N2 (ν) is substantially lower in Al2O3 DBD than in FBD. This is likely due to the lower electron number density in dielectric barrier discharges, which limit the excitation of vibrational states compared to ferroelectric barrier discharges.

Based on the theory explained in Methods, vibrational temperatures of N2 are fitted from the collected spectra as shown in Supporting Information Figure S6. As shown in Fig. 4b, the average vibrational temperatures in FBD are 1595 K and 885 K for pure N2 and N2/H2 mixtures, respectively. These results indicate that the addition of H2 reduces the N2 vibrational temperature, likely due to the introduction of additional energy transfer pathways in the plasma. Furthermore, this observation is confirmed at different total flow rates and gas compositions as shown in Supporting Information Figure S7 and Figure S8. To rule out thermal heating as the source of elevated vibrational temperatures, pure-rotational N2 CARS spectra were collected, as shown in Fig. 4c, to assess the rotational temperature, which approximates the translational temperature. The rotational temperature is modelled by comparing the experimental spectra with theory through a least-squares fitting routine, as shown in Supporting Information Figure S9. As shown in Fig. 4d, the difference in rotational temperature between pure N2 and N2/H2 plasmas is minimal, below 5 K. Furthermore, the rotational temperature differences between FBD and Al2O3 DBD are also minor, within 20 K. These small variations confirm that vibrational excitation is not significantly influenced by gas heating, but rather governed by the plasma’s non-equilibrium excitation dynamics.

Promoted synthesis of NH3 in ferroelectric barrier discharge
Figure 5 compares the time-resolved NH3 production in FBD and DBD using a stoichiometric gas mixture of 25% N2 and 75% H2 at a constant flow rate and pressure of 10 Torr. The NH3 concentrations are measured via laser absorption spectroscopy. Two key observations emerge from the comparison: (i) the incorporation of a ferroelectric barrier significantly enhances the ammonia yield, reaching nearly four times the amount produced in Al2O3 DBD, and (ii) the time required to reach a steady-state NH3 concentration is extended in FBD. Specifically, the steady-state NH3 mole fraction increases from ~150 ppm in Al2O3 DBD to about 550 ppm in FBD. It is worth noting that this enhancement is not limited to this specific condition but is also observed across different total flow rates and mixture compositions, as shown in Supporting Information Figure S10. This enhancement is attributed to the increased production of reactive species—namely N radicals, H radicals, ions (e.g., N2+) and vibrationally excited N2 molecules—in the FBD system. Furthermore, the extended transient time to steady-state NH3 concentration, ~20 seconds in FBD compared to 9 seconds in Al2O3 DBD, suggests the involvement of surface reactions in addition to gas-phase plasma chemistry44. Although surface chemistry is not the primary focus of this study, this observation indicates a synergistic effect between plasma activation and the barrier surface, even in the absence of externally loaded catalysts such as Ni or Co15. Furthermore, to place our NH3 measurements in the context of the global effort to improve the energy efficiency of plasma-assisted ammonia synthesis45,46, they are benchmarked against representative studies as shown in Table 2. However, a strict like-for-like comparison is not intended: system in this work was purpose-built for time-resolved laser diagnostics, with a small discharge area, no catalyst packing, and a low operating pressure and temperature, prioritizing control and observability over throughput.

Gas phase mechanisms in ferroelectric barrier discharge
To gain further insight into the mechanisms underlying the enhanced production of active species and ammonia, plasma kinetic modeling was performed. The modeling results, summarized in Fig. 6, focus on the key gas-phase reaction pathways responsible for the generation of N and H radicals. In N2/H2 plasma, H radicals are primarily generated through direct electron impact dissociation and via collisional H2 quenching involving N2*. Similarly, N radicals are initially formed by electron impact dissociation of N2 and subsequently through radical reactions such as NH+H→N+H2. Consistent with findings from our previous work39, plasma reaction pathways involving vibrationally excited species - H2 (ν) and N2 (ν) - are identified as important contributors to the production and consumption of radicals, thereby influencing NH3 formation in both the gas phase and on catalyst surfaces. As shown in Fig. 6a and Fig. 6c, H2 (ν, ν) actively participates in radical chemistry, which serves not only as a dominant N radical consumption source, but also contributes significantly to H radical production, highlighting the critical role of H2 (ν) in driving gas-phase ammonia formation. Additionally, Fig. 6b and Fig. 6d illustrate that N2 (ν) contributes to the formation of NNH via N2 (ν)+H→NNH. NNH may then engage in surface-mediated reaction steps, facilitating NH3 production through interactions with catalytic sites47.

Besides the importance of vibrationally excited species, a comparison between Al2O3 DBD and FBD plasma kinetics reveals notable shifts in reaction pathways, particularly with respect to ion chemistry. In FBD, the higher reduced electric field20 lead to increased electron energy delivery, which significantly enhances the formation and participation of ions. As shown in Fig. 6d, ion-related pathways account for a significant fraction of H radical formation and removal. For instance, H2++H2→H3++H, H2++N2→H+N2H+, and N2++H2→H+N2H+ together contribute almost 35% of total H generation, a striking contrast to the negligible ion contribution observed in Al2O3 DBD. These pathways reflect the enhanced ionization environment facilitated by higher electron densities and energies in FBD. On the consumption side, H radicals are also actively depleted through charge-transfer or proton-transfer processes involving H+ and other ions. Together, these findings indicate that ionic reactions, both generative and consumptive, play dual roles in shaping the steady-state concentration of H radicals under high-E/N plasma regimes, making them indispensable components in the overall plasma chemical network.

For nitrogen-related chemistry, similar trends are observed. Ion-mediated reaction pathways become more prominent in FBD. For example, the dissociative recombination of N2H+ becomes a non-negligible contributor to N production in FBD, whereas it is nearly absent in Al2O3 DBD, as shown in Fig. 6c, a. This increase in ion participation again reflects the enhanced ionization and electron-impact reactivity under high electric field conditions.

Beyond N and H radicals, NH is also a key intermediate in ammonia synthesis, both in the gas phase and on catalytic surfaces. Path flux analysis of NH is presented in Supporting Information Figure S11. In FBD, the NH flux from N+H(+M)→NH(+M) reaction becomes more prominent, rising from 2.51% to 26.49%, and an additional NH source emerges via the electron-induced decomposition of N2H+, which is absent in Al2O3 DBD, as shown in Figure S11. Overall, the results indicate that FBD reshapes NH generation by enhancing N radical chemistry and introducing new ion-driven channels.

While N2 (ν) appears to play a less significant role in gas-phase radical production compared to H2 (ν), its potential for preferential adsorption on catalyst surfaces suggests a more influential role in surface reactions. For instance, N2 (ν) could lower the apparent barrier for N-N bond cleavage and shift optimal catalysts toward metals that bind N weaklier9. While surface reactions are not the primary focus of this study, surfaces could indeed influence the overall reaction pathways, particularly by serving as a third body (M) in three-body processes such as the hydrogenation of NH and NH2 radicals and changing the catalytic reaction pathways via surface nitridation48. In conventional gas-phase three-body reactions (e.g., NH+H+M→NH2+M in Fig. 6b and Fig. 6d), the third body stabilizes the product by dissipating excess energy. Analogously, solid surfaces can act as energy sinks, enabling recombination or hydrogenation reactions. The synergistic interactions between plasma-generated species and surface adsorption processes may play a non-negligible role, especially in enhancing the utilization of short-lived intermediates like NH and NH2. Therefore, further studies are necessary to explain the mechanisms by which ferroelectric materials influence surface catalytic behavior, and to better understand their synergistic contributions to NH3 synthesis.

To summarize, this work demonstrates that the incorporation of a ferroelectric barrier into a non-equilibrium N2/H2 plasma discharge significantly increases the production of active radicals, ions, vibrationally excited nitrogen, and NH3. Results show that the PZT ferroelectric barrier discharge generates surface charge densities at least an order of magnitude greater than the conventional Al2O3 dielectric barrier discharges. OES measurements show that more ions (e.g., N2+*) are generated in FBD. In-situ, time-resolved measurements using fs-TALIF reveal that the ferroelectric barrier leads to N and H radical number densities up to ten times higher than those in Al2O3 DBD. CARS measurements indicate a drastic enhancement of the vibrational excitation of N2 (ν) and the N2 vibrational temperature, with detectable populations up to ν=2 and vibrational temperatures of 1595 K and 885 K for pure N2 and N2/H2 mixtures. In addition, laser absorption measurements reveal that nearly four times higher NH3 was produced in FBD relative to Al2O3 DBD under identical operating conditions. Parametric investigations over a broad range of mixture compositions and flow residence time further confirm the generality of the observed enhancements of active species generation and NH3 production in FBD compared to Al2O3 DBD. Complementary plasma kinetic modeling further reveals the importance of coupling reactions between radicals and vibrational excitation such as H2 (ν)+N→NH+H, N2 (ν)+H→NNH, and ion chemistry featuring N2+, H2+ and N2H+, supporting the conclusion that the synergy among elevated radical and ion production, enhanced vibrational excitation, and possible plasma-surface interactions facilitated by ferroelectric polarization plays a key role in modifying plasma kinetics and enabling low-temperature plasma reactions. These findings provide not only critical insight into the mechanisms of ferroelectric plasma-enhanced NH3 production, but also clear guidance on controlling non-equilibrium surface charge production, plasma chemistry, and active species for efficient plasma catalysis with ferroelectric materials.

Methods
Plasma discharge configuration
The plasma was generated in a plate-to-plate configuration as shown in Fig. 1a. Both the ferroelectric lead zirconate titanate (Pb(ZrxTi1-x)O3) from Steiner & Martins, Inc., and the dielectric Al2O3 from McMaster-Carr were processed to the dimensions of 4.5 cm × 1.7 cm × 0.12 cm. These two electrodes were separated by a 5 mm gap and enclosed in a 110 mm-long, 24 mm × 11 mm rectangular quartz channel with a wall thickness of 2 mm. In all in-situ diagnostic experiments, both ferroelectric barrier discharge and dielectric barrier discharge were operated using an AC power supply (PVM500/DIDRIVE10, Amazing1) at a frequency of 20 kHz and an applied voltage of 2.6 kV (peak to peak). Nitrogen and hydrogen gases (99.9999%, Airgas USA, LLC) flowed into the quartz cell with a fixed residence time of 0.05 seconds (i.e., 100 sccm total flow rate unless otherwise labeled) between the electrodes at a pressure of 10 torr. For the N2/H2 mixture, the ratio between N2 and H2 is 1:3 (i.e., 25% N2 plus 75% H2) unless otherwise labeled.

To ensure optimal ferroelectric performance in the FBD configuration, the PZT plates are pre-poled prior to operation. According to the manufacturer and standard industrial practice, ferroelectric poling is performed along the thickness direction by applying a high DC electric field at elevated temperature. Standard poling protocols involve heating the ceramic to approximately 100–150 °C (below the Curie temperature 320 °C), immersing it in a dielectric medium such as silicone oil, and applying a DC electric field of 2–4 kV/mm for 10–30 minutes. The field is maintained during cooling to stabilize the spontaneous polarization along the applied axis, thereby ensuring long-range dipole alignment and stable macroscopic response. While the exact parameters are proprietary and not disclosed by the manufacturer, the product is supplied in a fully poled and application-ready state. In this work, all experiments were conducted using the same factory-poled ceramic plate, with no post-processing applied. This uniformity guarantees that all data reflect consistent material conditions and that observed performance trends derives solely from reactor design and operating parameters, not from variability in polarization state.

Electrical measurements
A reference capacitor, Cref = 10 nF (Digi-Key, 399-12395-ND), is placed in series with the plasma cell. The applied voltage Ucell and the voltage drop across the reference capacitor Uref are monitored using two high-voltage probes (Tektronix, P6015A) connected to a digital oscilloscope (Tektronix, TDS 2012B). The total current through the plasma, including any parallel parasitic components, is monitored using a current monitor (Pearson 6585). The equivalent circuit of the system and detailed explanation can be found in our previous work20.

Two-photon absorption laser-induced fluorescence (TALIF)
Figure 7a shows the experimental setup of in-situ femtosecond two-photon absorption laser-induced fluorescence (fs-TALIF) for detecting H and N radicals in a ferroelectric barrier discharge. This setup consists of a femtosecond (fs) laser system, an FBD plasma system, and an ICCD camera with a Nikon AF-S NIKKOR 50mm lens. The fs laser system consists of a Ti:sapphire oscillator, an ultrafast amplifier, and an optical parametric amplifier (OPA). The OPA (TOPAS NIRUVIS, Light Conversion) outputs UV fs laser pulses with a pulse energy of ~3.7 μJ for H and ~2.7 μJ for N at central wavelengths around 205.1 nm (theoretically at 205.08 nm) for H and 206.7 nm (theoretically at 206.65 nm) for N at 1 kHz via a series of nonlinear optical processes, including second-harmonic generation and sum-frequency generation. The fs laser beam is focused into a rectangular FBD plasma reactor, and excites the 1s 2S1/2→3d 2D3/2,5/2 transition of the H radical (or the 2p3 4S3/2→3p 4S3/2 transition of the N radical)49. The H fluorescence signal at 656 nm and N fluorescence signal at 745 nm are captured by an ICCD camera (PI-MAX 4). For H fluorescence, a bandpass filter with a full-width-at-half-maximum (FWHM) of 10 nm centered at 656 nm is applied in front of the camera lens to block any laser scatter and plasma emissions, while for N fluorescence, a bandpass filter centered at 745 nm with 10 nm FWHM is used. The intensified camera with a 110 ns gate is synchronized with the laser using control electronics to enable time-resolved measurement during a single voltage cycle.

Before using fs-TALIF to study the impact of the ferroelectric discharge on plasma chemistry, we validate the quadratic relationship between the signal and the laser pulse energy. As shown in Supporting Information Figure S12, we plotted the fs-TALIF signal as a function of the square of pulse energy. The fs-TALIF signal of N follows a quadratic relationship with the laser pulse energy under 2.9 μJ. The fs-TALIF signal of H also follows a quadratic relationship with the laser pulse energy under 4.1 μJ. These quadratic relationships validate that our fs-TALIF measurements have negligible photolytic and stimulated emission interferences.

To obtain the absolute concentrations of H and N radicals, the TALIF measurements are calibrated using the same pressure Kr-TALIF measurements, since H, N, and Kr have similar excitation wavelengths with minor changes39. The absolute density of the target species (denoted as Ni) is determined by comparing to the known number density of the calibration Kr (NKr) as follows50,

Ni = NKr (ηT)Kr a2!3Kr ∫0 I2(t)dtKr ν2 0i σ(2)i g(δν)i SDi
(ηT)i a2!3i ∫0 I2(t)dt i ν2 0Kr σ(2)Kr g(δν)Kr S DKr

where η is the quantum efficiency of the camera, T is the transmission of the signal collection optics at the fluorescence wavelength, a2!3 = A2!3 / (A2!3 + Q) is the fluorescence quantum yield where A2!3 is the spontaneous emission rate and Q is the collisional quenching rate, respectively, and τ is the natural lifetime of the species. In addition, kq is the quenching coefficient of the collisional partner with q taken to be the major species N2 and/or H2, and nq is the number density of the collisional partner calculated based on the ideal gas law with the approximate mole fractions. ∫0 I2(t)dt is proportional to the square of the used laser pulse energy, ν0 is the central wavelength of the excitation laser, σ(2) is the two-photon absorption cross section, g(δν) is the normalized two-photon absorption line profile, and SD is measured fluorescence signal. The above calibration parameters are listed in the Supporting Information Table S1.

Coherent anti-Stokes Raman scattering (CARS)
Hybrid fs/ps coherent anti-Stokes Raman scattering (fs/ps CARS) is a nonlinear spectroscopic technique that provides spatially and temporally resolved vibrational and rotational temperature measurements in non-equilibrium plasmas. In hybrid fs/ps CARS, two broadband fs pulses (pump and Stokes) cover a broad range of Raman transitions in the target molecule. A narrowband ps probe pulse scatters off the excited Raman coherence and the CARS signal is generated through the nonlinear four-wave mixing process. The non-resonant background is minimized by introducing a time delay to the probe pulse. In our 3-beam hybrid fs/ps CARS system, the vibrational N2 Raman transitions are targeted by the 675 nm and 800 nm pulses. Due to the broadband nature of the fs pulses, the 800 nm pulse is able to effectively excite the pure-rotational N2 Raman coherence. The 400 nm probe pulse samples both the vibrational and pure-rotational Raman coherence simultaneously, and a bandpass filter is used to separate the probe pulse from the CARS signal. A grating-based spectrometer is used to differentiate the vibrational and pure-rotational CARS signal.

The CARS signal intensity is modeled as the square magnitude of the product between the probe electric field (Epr) and the combined resonant (Pres) and non-resonant (Pnres) polarizations43,

ICARS(t) ∝ |Epr(t) [Pres(t) + Pnres(t)]|2

where Pnres is modeled as the product between the pump electric field and the complex conjugate of the Stokes electric field (Es*). The resonant polarization can be expressed as43,51

Pres(t, τ12, τ23) = ℏ i 3 ∫01 ∫01 dt2 h RCARS(0, t2, 0) Es*(t+τ23-t2) Ep(t+τ23+τ12-t2) ei(ω1-ω2)t2

where τ12 is the time delay between the pump and Stokes beams, τ23 is the time delay between the Stokes and probe beams, and RCARS is the molecular response function. The N2 Q-branch vibrational molecular response function is defined as52,

RCARS(t) = ∑ν ∑J Iν,J;ν+1,J exp(-iω ν,J;ν+1,J - Γ ν,J;ν+1,J) t

where ω ν,J;v+1,J is the transition frequency, Γ ν,J;v+1,J is the Raman linewidth, ν is the vibrational quantum number, and J is the rotational quantum number. The Boltzmann-weighted Raman transition intensity Iν,J;ν+1,J is defined as53,

Iν,J;ν+1,J ∝ ΔNν,J;ν+1,J (ν+1) [a02 δ JJ0 F a(J) + 4 4 5 b JJ0 (γ0)2 Fγ(J)]

where a0 and γ0 are the Raman polarizability tensor invariants, F(J) is the Herman-Wallis factor, and b JJ0 is the Placzek-Teller coefficient. It is worth noting that the Raman transition intensity scales with ν+1. The S-branch pure-rotational molecular response function is defined in a similar way.

The vibrational and rotational temperatures are calculated from the experimental spectra by comparing with theory through least-squares curve fitting. First, 1000 laser shots were background-subtracted and averaged. The averaged spectrum was then divided by the non-resonant argon spectrum to correct for the Raman excitation efficiency at different wavelengths. The spectrometer grating and the camera’s quantum efficiency were also considered during data processing. For the spectral fitting process, a total of 7 parameters are determined with room temperature reference spectra. These parameters are: probe time delay, probe linewidth, non-resonant background scalar, non-resonant background phase shift, instrument width, and vertical and horizontal shift. After the 7 parameters are known, they are fixed in the simulation. The rotational temperature is then floated and the best-fit values are calculated from the N2 pure-rotational spectra, as shown in Supporting Information Figure S4. After the rotational temperature is known, we fix the rotational temperature and calculate the vibrational temperature from the Q-branch N2 vibrational spectra.

Figure 7c shows the experimental setup of the 3-beam fs/ps coherent anti-Stokes Raman scattering (CARS) system for detecting N2 (ν). The Ti:Sapphire amplifier (Astrella, Coherent Inc.) outputs 100 fs pulses centered near 800 nm at 1 kHz. The output pulse energy is ≈7 mJ and is divided into three legs. One leg (≈4 mJ) is used to pump the optical parametric amplifier (TOPAS NIRUVIS, Light Conversion), which is centered at 675 nm to target the Q-branch N2 Raman transitions43. Another 1 mJ is served as the Stokes beam, and the rest of the 2 mJ is used to generate the 400 nm narrowband probe pulse. A second harmonic bandwidth compressor (SHBC) is used to convert the 100 fs beam into a ps-duration probe beam. Two delay lines with linear translational stages are used to achieve optimal timing between the pump, Stokes and probe pulses. Following the planar BOXCARS phase matching scheme43, a 250 mm lens is used to focus the three input beams. In this phase matching scheme, the vibrational CARS signal partially overlaps with the pure-rotational CARS signal, which is generated at the same location as the probe pulse on the collimating lens. The vibrational CARS signal is generated by the pump and Stokes pair, while the pure-rotational signal is generated by the Stokes beam. A 2.5 ps probe time delay is used for the vibrational CARS spectra, while an 8.5 ps probe delay is applied to suppress the non-resonant background of the pure-rotational CARS signal. The CARS signal is focused with a 75 mm lens into a spectrometer (2400 l/mm grating) and sampled by an intensified CCD (ICCD) camera. The spectrometer is centered at 367.50 nm and 393.47 nm for vibrational and pure-rotational CARS, respectively. The vibrational CARS signal can be easily separated from the pure-rotational CARS signal by tuning the spectrometer grating. The camera is synchronized with the fs laser and AC power supply with a delay generator (SRS DG645). For each condition, 50 frames are saved on average, with 20 exposures of 350 ns per frame.

NH3 measurements
Figure 7(b) shows the experimental setup of laser absorption for time-dependent ammonia measurements. The Ti:Sapphire amplifier (Astrella, Coherent Inc.) outputs 100 fs pulses centered near 800 nm at 1 kHz. The optical parametric amplifier (TOPAS NIRUVIS, Light Conversion) is used to generate 201 nm pulses via a series of nonlinear optical processes, including second-harmonic generation and sum-frequency generation, with a pulse energy of ~6 μJ to target the A e1 A 00 X e1 A 0 2 1 transition of the ammonia ν2 bending mode54. Two mirrors are used to perform 5-pass absorption measurements through the plasma cell with an optical length of 22.5*5=112.5 cm. The signal is focused with a 125 mm lens into a spectrometer and sampled by an intensified CCD (ICCD) camera. The camera is synchronized with the fs laser and AC power supply with a delay generator (SRS DG645). A gate width of 130 ns is used for the camera. The baseline of the no-plasma condition is used to calculate ammonia concentration based on the Beer-Lambert law: ln(I0/I) = σLn, where I0 and I are light intensities after the passage of the cell with and without plasma, σ is the ammonia absorption cross-section, L is the optical length, and n is the ammonia number density55.

Optical emission spectroscopy (OES)
The emission spectra from the plasma discharge are acquired by using a miniature spectrometer (Ocean Optics, USB2000+) via an optical fiber placed right at the side of the quartz cell wall, with an acquisition time of 1 s. The spectra are background-subtracted.

Plasma kinetic modeling
The path flux analysis in this study is conducted using a hybrid ZDPlasKin-CHEMKIN model developed at Princeton University56–58. This model couples the plasma kinetics solver ZDPlasKin59 with the combustion kinetics solver CHEMKIN60 through a time-splitting scheme. Electron impact reaction rate constants and transport parameters are computed using the Boltzmann equation solver BOLSIG+61, which is integrated into ZDPlasKin. This in-house model has been extensively validated against experimental data in previous studies39,56,62,63, with the governing equations detailed in ref. 56. The recently developed N2/H2 plasma chemistry for NH3 synthesis57,63,64 is used in this work. This kinetic model has been rigorously validated against experimental measurements of temperature and the number densities of radicals and excited species. It comprises two components: a plasma kinetic sub-mechanism, which includes electrons, ions, and electronically/vibrationally excited species; and a gas-phase sub-mechanism, which accounts for ground-state species. The model includes 50 species, 494 reactions in the plasma kinetic mechanism, and 51 reactions in the gas-phase mechanism. The plasma kinetics sub-mechanism captures key processes such as electron impact vibrational and electronic excitation, dissociation, ionization, attachment, quenching, energy transfer, charge exchange, and both ion-ion and electron-ion recombination. All reactions related to the path flux analysis of N, H, and NH species are listed in the Supporting Information Tables S2–S4.

To simulate the AC dielectric barrier discharge plasma, the methodology developed by van’t Veer et al37. is implemented within the hybrid ZDPlasKin-CHEMKIN framework. Given the filamentary nature of AC plasmas, the model represents micro-discharges by applying periodic triangular pulses of power density. The experimentally measured plasma power is distributed across these pulses, with the peak power, pulsed duration, and frequency fitted to experimental data. In this study, 50 triangular pulses, each with a duration of 400 ns at a discharge frequency of 119 kHz, are applied over the full residence time.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The article presents a rapid directional electrodynamic decomposition (DED) method for stripping freestanding oxide membranes using a conductive LaNiO₃ sacrificial layer. Compared to traditional soaking methods, DED improves the release rate by two orders of magnitude (up to 600 mm²/min), enables wafer-scale (up to 12-inch) crack-free film transfer, and maintains the structural and functional integrity of perovskite-based membranes, facilitating their use in flexible electronics and industrial semiconductor integration. The following questions and suggestions should be addressed prior to publication in Nature Communications:\n(1) The mechanism of “directional electrodynamic decomposition” (DED) is introduced but lacks a detailed theoretical foundation or comparison with established electrochemical etching models.\n(2) The manuscript emphasizes the increased etching rate but provides limited comparison of overall performance metrics with other freestanding film fabrication methods. : How does DED quantitatively compare with other state-of-the-art methods beyond stripping rate (e.g., in terms of power consumption, reproducibility, and membrane quality)?\n(3) The claim of “crack-free” and “flat” membranes is qualitative. More quantitative defect density or surface roughness analysis could substantiate these claims. : Is there quantification of defects, wrinkles, or residual stress in the stripped membranes (e.g., via TEM, AFM, or Raman mapping)?\n(4) While structural characterization is thorough, electrical performance (e.g., breakdown voltage, leakage current) post-DED is not well covered, especially for large-area samples. How are the electrical or ferroelectric properties of the membranes preserved post-release?\n(5) Potential contamination or electrochemical degradation byproducts are not discussed. Are there any secondary reactions or by-products (e.g., La ions in solution) that could impact membrane integrity or recyclability of the substrate?\n(6) While a large-scale film is shown, there’s limited data on spatial homogeneity or yield statistics. Was uniformity (thickness, crystallinity) across the 12-inch film evaluated comprehensively (e.g., mapping or statistical analysis)?\n(7) The manuscript mentions reuse but lacks experimental data on reusability or long-term process stability. : How many times can the process be repeated on the same substrate without loss of performance?\n(8) What is the detailed electrochemical decomposition pathway of LaNiO₃ in acetic acid under an electric field? Are intermediate phases formed during the DED process (e.g., La-based complexes)? If so, how do they affect the film or etching dynamics?\n(9) Does the current density uniform across the entire sample during DED? Were 3D electric field and current flow simulations performed to support the directional aspect of DED?\n(10) How do local variations affect the etch rate or membrane quality? Are there voltage or current thresholds where electrolysis of the solution or breakdown of target layer occurs?\n(11) Are local strain variations mapped (e.g., via TEM or synchrotron microdiffraction) before and after stripping to understand relaxation behavior? Is the observed enhancement in Bader charge supported by in situ experimental validation, such as electrochemical impedance spectroscopy (EIS) or Raman under bias?", "reviewer_2": "This manuscript by Li et al. reports a novel technique for preparing freestanding membranes of perovskite-type dielectric materials with preferential crystal orientation, named DED. I, the reviewer, recognized that the technique proposed in the present manuscript is unique and will be useful for manufacturing thin-film devices coupled with freestanding membranes and versatile substrates or wafers of non-perovskite type materials. However, I also felt that the manuscript tends to report the experimental results of DED, but insufficient explanation for its basic mechanism. Also, I hardly found any applicability for the research concept of using PZ films (60 nm thick) as a target of DED, as well as the quality or physical properties of the resulting thin-film devices.\nIn the present state, I that we cannot accept the manuscript for the publication of the present manuscript on Nature Communications as it is because it has never provided reasonable evidence (both of experimentally and theoretically) sufficient for certifying the author’s proposal. If the authors would like to release their achievement, fundamental revision with extreme reconstruction will be required for data, explanation, and discussion in the present manuscript, where the submission to any other journal (e.g., Scientific Reports) can be one realistic choice for some situations.\n“Comments on DED”\n- Concept as well as experimental results are significantly interesting. However, there is almost no explanation for basic mechanism of the chemical reaction. chemical formulae should be proposed in the main document, at least, to clarify the reaction scheme in the actual system.\n- The reaction scheme described in Fig. 1d and 1e are totally not valid. If the anode (i.e., positively-charged electrode) oxidize the H2O to form H+, it requires threshold voltage (theoretically > 1.23 V, practically > 2 V) and significant reaction won’t occur under lower voltage (e.g., 0.1 V in Fig. 2a). Moreover, if the reaction scheme is true, the reaction will occur without weak acid (i.e., acetic acid) because H+ will deliver from H2O independent of the concentration of acids. Reference experiment without weak acid should be performed to certify the reaction scheme, as well as verification experiments to confirm the threshold voltage of redox reactions.\n- For confirming the versatility of DED, it should be applied for piezoelectric (or dielectric) membranes with various thickness.\n“Comments on PZ”\n- At first, I understand that we will not fabricate PZ films by following the instruction in the supporting information (1.2 PbZrO3). Please read the description again carefully to check typographical or technical errors included in the explanation.\n- Totally I could not find any applicability or reasonability for introducing PZ in this research: Pb(Zr,Ti)O3 or PbTiO3 should be utilized as ferroelectric layers if we aim to focus on piezoelectric devices, in general. Research plan using PZ rather than PZT and PT is significantly unreasonable and unrealistic from the viewpoint of device fabrication.\n- Even if the author would like to realize ferroelectric (or non-antiferroelectric) PZ films in DED process, the experimental results shown in the manuscript did not work efficiently for supporting the author’s concept. P-E loops (in Fig. 4e and 4g) are so-called “leaky” which includes high-level current conduction, that prevent the measurement of adequate switching current to identify their character (ferroelectric or antiferroelectric); the identification of FE and AF shall be based on the shape of saturated P-E loop, not only on the switching current.\n- Thicknesses of the ferroelectric layer (60 nm) is generally unreasonable for piezoelectric application. It can be a major reason for insufficient quality of the PZ films which causes leakage current conduction. Thicker layers above 100 nm should be considered for the application of piezoelectric sensors or actuators.\n- If the authors would like to discuss the ferroelectricity of PZ from theoretical viewpoint, detailed explanation and discussion should be shown in the main document, not only in the supporting information. I hardly agree with the author’s claim for the crystal symmetry which is explained by data in Figs. 4b and 4c because of the lack of explanation and discussion, as well as poor resolution of figure images.\n- PFM data is not sufficient for certifying the piezoelectric character of the resulting films. The measurement of strain – electric field (S-E) curves is favorable to confirming that it will not be electrostrictive strain or not, and then to determine the piezoelectric constants for evaluating the device performance.\n- Performance of the piezoelectric membrane is significantly important when it is compared with the competitive devices, i.e., piezoelectric sensors using ferroelectric polymers such as a PVDF which can be formed by low-temperature deposition process: the device concept shall be reconsidered if the performance of PZ membrane is comparable or inferior to the polymer-based ferroelectrics.\n- I am wondering that the description of “distinct 180°. domain switching (Fig. 4f)” is adequate or not from the viewpoint of domain engineering, which is related to the existence or non-existence of tilted domain structure (e.g., 109° and 71° domains for epitaxial BFO films). Detailed discussion based on the crystal symmetry of PZ (as well as its crystal orientation or domain structure) should be included.\n- Again, it looks significantly hard to accept the concept for applying PZ in the present manuscript because it does not support the author’s proposal.\n“Comments on other materials”\n- It looks unfair that the ferroelectric properties of BFO membrane was evaluated only by SGH data. P-E measurement shall be performed as similarly to other materials because it includes the evaluation for the quality of BFO membranes (e.g., microstructural cracks or defects which is hardly evaluated by SGH manner).\n- Dielectric constant of STO films (k = 67.1, in Extended Data Fig. 15b) is significantly lower than conventional data (typically k > 100). Quality of STO membranes should be evaluated, as well as BFO membranes.\n“Comments on manuscript document”\n- The present manuscript still includes typographical errors or misinformation in the main document as well as supporting information. Document check (spelling & grammar) in a more careful manner will be required.", "reviewer_3": "The authors describe a novel methodology for creating freestanding crystalline membranes that utilizes electrochemically drive decomposition of sacrificial etching layers with higher electrical conductivity than the desired membrane layers. This directional electrodynamic decomposition (DED) method shows improvement over other chemical etch release processes in the etch rates that can be achieved, the thickness of sacrificial layers that can be used, and the flatness of the resulting membranes. The authors present examples of successful membrane separation, post-separation characterization to verify membrane quality, and an etching mechanism that is supported by DFT calculations. This work represents a remarkable technical achievement that will be of interest throughout the oxide semiconductor community and industry.\nThe authors describe some limitations to the materials for which this technique can be applied including chemical compatibility and lattice matching. However the applicability of the technique is driven in part by the difference in conductivity between the membrane layer and the sacrificial layer (here LaNiO3). The manuscript would benefit from a quantitative discussion of difference in conductivity of the layers needed for the DED method to be effective and/or some commentary on how the etch processes parameters may need to be adjusted as the conductivity of the layers approach one another.\nThis reviewer believes this work should be published with a few additional comments about the applicability and limitations of the DED method."}, "author_response": "Dear Reviewers,\nThe authors highly appreciate the reviewing and the reviewers’ comments on our\nmanuscript entitled “Efficient electrodynamic stripping for 12-inch wafer-scale\nfreestanding ferroelectric membranes” (NCOMMS-25-33496-T). The comments and\nsuggestions are all valuable and very helpful for revising and improving the quality of\nthe manuscript. We have revised the manuscript point by point according to the\ncomments of the reviewers. The revised text was marked as a blue highlighted font in\nthe manuscript or supporting information. We believe that the present revised\nmanuscript is more coherent and articulate after the revisions. The detailed corrections\nare listed as follows.\nReviewer #1 (Remarks to the Author):\nThe article presents a rapid directional electrodynamic decomposition (DED)\nmethod for stripping freestanding oxide membranes using a conductive LaNiO\n3\nsacrificial layer. Compared to traditional soaking methods, DED improves the release\nrate by two orders of magnitude (up to 600 mm2/min), enables wafer-scale (up to 12-\ninch) crack-free film transfer, and maintains the structural and functional integrity of\nperovskite-based membranes, facilitating their use in flexible electronics and industrial\nsemiconductor integration. The following questions and suggestions should be\naddressed prior to publication in Nature Communications:\nResponse: Thank you very much for appreciating the content of our manuscript, and\nyour constructive suggestions have been a great help in improving our content. More\ndetails have been supplemented and answered one by one in the following replies.\n1. The mechanism of “directional electrodynamic decomposition” (DED) is\nintroduced but lacks a detailed theoretical foundation or comparison with established\nelectrochemical etching models.\nResponse: Thank you very much for your helpful suggestion. In fact, DED process was\nconsidered as an electrodynamic decomposition process. The electric field accelerates\nthe LaNiO +6H+ = La3++Ni3++3H O chemical reactions, which is a slow spontaneous\n3 2\ndecomposition process during the immersion process. The electric field has driven a\nsignificant increase in the preparation efficiency of functional oxide freestanding\nmembranes, but no new redox reaction was generated. Under the action of electric field,\nthe CH COOH electrolyte obtains the power to overcome the interface friction, and can\n3\nmove rapidly and directionally, and decompose the sacrificial layer quickly, which\n1\neffectively improve the characteristics of the solid-liquid interface and overcome the\nresistance caused by surface tension. In this process, the decomposition of water into\nhydrogen and oxygen will act as an additional electrolytic reaction. In addition, first-\nprinciples calculations indicate that the electric field will enhance the affinity of the\nacetate molecule and the La ions (Fig. 3a). This indicates that La3+ is mainly involved\nin the decomposition reaction, and it is difficult to lose electrons and participate in redox\nreaction. This further ruled out the occurrence of electrochemical etching. Considering\nthe reviewer’s suggestion, we have highlighted this part in the revised manuscript.\nLine 136-148 in the revised manuscript: “The current will preferentially flow from\nthe acetic acid electrolyte to the sacrificial layer as they are both conductive. Meanwhile,\nunder the action of electric field, the electrolyte obtains the power to overcome the\ninterface friction, and can move rapidly and directionally, and decompose the sacrificial\nlayer quickly, which effectively improve the characteristics of the solid-liquid interface\nand overcome the resistance caused by surface tension (Fig. 1e). The\nLaNiO +6CH COOH = La(CH COO) + Ni(CH COO) +3H O chemical reactions will\n3 3 3 3 3 3 2\ntake place, subsequently, the salt substances will re-dissolve in the solution. The electric\nfield only accelerates the reaction rate without generating new redox reactions. The\ndecomposition of water into hydrogen and oxygen will act an additional reaction. There\nis a side reaction in the positive electrode, which will produce hydrogen ions, conducive\nto accelerating the decomposition of the sacrificial layer. And there are no solid by-\nproducts.”\nLine 149-151 in the revised manuscript: “Before DED, through exploration we\nfound that the weak acid can dissolve LNO, and a slow spontaneous decomposition\nprocess of LaNiO +6H+ = La3++Ni3++3H O chemical reactions will act during the\n3 2\nimmersion process.”\nLine 265-266 in the revised manuscript: “In addition, these findings supported the\nelectrocatalysis of electric field acceleration.”\n2. The manuscript emphasizes the increased etching rate but provides limited\ncomparison of overall performance metrics with other freestanding film fabrication\nmethods: How does DED quantitatively compare with other state-of-the-art methods\nbeyond stripping rate (e.g., in terms of power consumption, reproducibility, and\nmembrane quality)?\nResponse: Thank you for your valuable suggestion. On the one hand, the reviewer may\nmainly focus on the preparation process of the layered materials such as graphene. A\nsimple “tugging” operation can yield high-quality flexible two-dimensional materials\n[Science 2004, 306(5696): 666-669; Sci. Adv. 2020, 6(44): eabc6601]. However, this\n2\nmethod is not applicable to a series of high-performance oxide freestanding membranes.\nOn the other hand, currently, the soaking method is the most common approach [Nat.\nMater. 2016, 15(12): 1255-1260; Science 2024, 383(6681): 388-394; Adv. Mater. 2024,\n36(15): 2307682]. In this field, the method of using decomposable sacrificial layers is\nstill employed as the key approach for fabricating freestanding single-crystal oxide\nfunctional membranes. Although Zhang et al. claimed that the weak coupling of Pb\nhybrid bonds could enable the separation of Pb-based perovskite films, the application\nscope of this method is rather limited [Nature 641, 98-105 (2025)]. The decomposition\nrate is the main bottleneck for obtaining large-area and high-quality freestanding oxide\nfilms through the soaking method. In this work, the DED process means that through a\nspecific electric field or device design, the ions in the electrolyte move in a\npredetermined direction, to achieve the decomposition reaction of the sacrificial layer.\nIt is worth noting that the decomposition of the sacrificial layer is necessary. Our aim\nis to prepare high-performance oxide freestanding membranes. This is different from\nthe flexible two-dimensional materials prepared by utilizing surface tension, as well as\nthe freestanding films obtained through immersion methods.\nFirstly, the release rate has been improved from 5 mm2/min of the traditional\nsoaking to 600 mm2/min of the DED method, which is two orders of magnitude\nimprovement, and not limited by thickness and area size. Although applying an electric\nfield below 25 V increases the energy consumption, the preparation efficiency is en-\nhanced by approximately 120 times. Secondly, this ultra-fast release rate prevents the\nfilm from bulging and thus ensures a smooth and flat surface (Fig. 2c). And the quality\nof the freestanding film (crack density is lower than 2.28×10-3 μm/μm2, see Question 3\nfor details) and the number of times the substrate (more than 20 times, see Question 5\nfor details) can be used are significantly improved. Lastly, we obtained a series of\nfreestanding single-crystal oxide functional membranes with outstanding performance,\nsuch as PbZrO , BiFeO , and SrTiO . Considering the reviewer’s suggestion, we have\n3 3 3\nstrengthened the domain limitations of this technology. Although applying an electric\nfield below 25 V increases the energy consumption, the preparation efficiency is en-\nhanced by approximately 120 times.\nLine 1 in the revised manuscript: “Efficient electrodynamic stripping for 12-\ninch wafer-scale freestanding ferroelectric oxide membranes”.\nLine 50-51 in the revised manuscript: “Key words: Freestanding, Oxide\nmembrane, Ferroelectric, Directional electrodynamic decomposition”\n3. The claim of “crack-free” and “flat” membranes is qualitative. More\nquantitative defect density or surface roughness analysis could substantiate these claims:\n(e.g., via TEM, AFM, or Raman mapping)?\nResponse: Thank you for your valuable suggestion. As you said, we do indeed need to\nfurther quantify the crack density in the film to ensure that the description in the\nmanuscript is reasonable. We have used the scanning electron microscope (SEM) to\ninvestigate the surface cracks of the freestanding PbZrO membranes. In fact, we did\n3\nnot observe any cracks within the millimeter scale (Fig. R1a). However, there are still\nsome cracks in the films with 10×10 mm2 size (Fig. R1b). We calculated the crack\ndensity to be about 2.28×10-3 μm/μm2 based on the highest crack areas in it (Fig. R1c).\nThis value is lower than the crack density found in the freestanding membranes\nobtained by T-Sr Al O with about 5.90×10-2 μm/μm2 (Figure S23-S28 in Science)\n4 2 7\n[Science 2024, 383(6681): 388-394]. The cracks in our work originated from the\nmechanical stress damage during the transfer process, rather than the stress relaxation\nduring the decomposition of the sacrificial layer. During the sacrificial layer\ndecomposition process, all of our freestanding thin films exhibited the phenomenon of\n“crack-free and flat”, which was precisely the result of the DED technology (Fig. 2d).\nWhen the freestanding thin films were transferred onto the PDMS, a few cracks will be\ngenerated. When transferred again onto the Si substrate, enhanced cracks will be\ngenerated. After Raman mapping analysis, we were delighted to find that the transferred\nPZO thin film exhibits highly uniform stress distribution across different regions (Fig.\nR2). This excellent property undoubtedly lays a solid foundation for its future wide-\nranging applications. Considering the reviewer’s suggestion, we have added this part in\nthe revised manuscript.\nFigure R1. SEM images of the freestanding PbZrO membranes. (a) SEM images with\n3\n2.0×1.5 mm2 of the freestanding PbZrO membranes.(b) Large size SEM image of the\n3\nfreestanding PbZrO membranes. (c) SEM image with cracks for the freestanding PbZrO\n3 3\n4\nmembranes.\nFigure R2. Raman mapping of the PbZrO thin film transferred onto the Si/Pt substrate.\nreduction of the thickness of the sacrificial layer, the target layer of PZO films presents\ncrack-free and wrinkle-free at the millimeter size (Extended Data Fig. 6).”\nPage 11 in the revised supporting information: “\nExtended Data Fig. 6 SEM images of the freestanding PZO membranes. (a) SEM\nimages with 2.0×1.5 mm2 of the freestanding PZO membranes. (b) Large size SEM\nimage of the freestanding PZO membranes. (c) SEM image with cracks for the\nfreestanding PZO membranes.\nWe have used SEM to investigate the surface cracks of the freestanding PZO\nmembranes. In fact, we did not observe any cracks within the millimeter scale\n(Extended Data Fig. 6a). However, there are still some cracks in the films with 10×10\nmm2 size (Extended Data Fig. 6b). We calculated the crack density to be about 2.28×10-\n3 μm/μm2 based on the highest crack areas in it (Extended Data Fig. 6c). This value is\nlower than the crack density found in the freestanding membranes obtained by T-\nSr Al O with about 5.90×10-2 μm/μm2 (Figure S23-S28 in Science) 4. The cracks in\n4 2 7\nour work originated from the mechanical stress damage during the transfer process,\nrather than the stress relaxation during the decomposition of the sacrificial layer. During\nthe sacrificial layer decomposition process, all of our freestanding thin films exhibited\nthe phenomenon of “crack-free and flat”, which was precisely the result of the DED\ntechnology (Fig. 2d).”\n4. While structural characterization is thorough, electrical performance (e.g.,\nbreakdown voltage, leakage current) post-DED is not well covered, especially for large-\narea samples. How are the electrical or ferroelectric properties of the membranes\npreserved post-release?\nResponse: Thank you for your helpful suggestion. As you said, the electrical properties\nof thin films are indeed the key issue before and after the thin films is stripped. In fact,\nwe have already tested the piezoelectric properties of the 3-inch freestanding thin film\n(Extended Data Fig. 22 - Extended Data Fig. 24). The results show that the freestanding\n5\nthin film possesses uniform piezoelectric properties, directly supporting the generation\nof high-quality freestanding thin films through DED method. We have added the\nleakage current curves of the 12-inch polycrystalline freestanding PbZrO thin film\n3\n(Figure. R3), which is almost the same as that of the PbZrO thin films with about 1×10-\n3\n2 μA/cm2 before stripping. Meanwhile, all the positions did not exhibit any breakdown\nphenomenon under 10 V, indicating that they have the outstanding and uniform\nbreakdown resistance. This indicates that during the formation process of large-area\nfreestanding thin films, the thin films still maintain excellent ferroelectric structural\nproperties.\nFigure R3. Leakage current curves of the 12-inch PZO freestanding thin films before and\nafter stripping.\nLine 458-460 in the revised manuscript: “The electrical property (leakage current)\nof the 12-inch freestanding PZO film also remains at the magnitude of about 10-2\nμA/cm2 of the value before stripping (Extended Data Fig. 28).”\nPage 24 in the revised supporting information: “Extended Data Fig. 28 Leakage\ncurrent curves of the 12-inch PZO freestanding thin films before and after\nstripping. ”\n5. Potential contamination or electrochemical degradation byproducts are not\ndiscussed. Are there any secondary reactions or by-products (e.g., La ions in solution)\nthat could impact membrane integrity or recyclability of the substrate?\nLaNiO in a weak acid solution is the LaNiO +6H+ = La3++Ni3++3H O, which is a slow\n3 3 2\nspontaneous decomposition process during the immersion process. And the electric\nfield accelerates the LaNiO +6H+ = La3++Ni3++3H O chemical reactions. It can be seen\n3 2\nfrom the reaction equation that there are by-products of La3+ and Ni3+ in solution, but\nthere are no solid by-products. There is only 2H O = 2H ↑+O ↑ side reaction under the\n2 2 2\ninfluence of the electric field. We further focused on the reproducibility of the substrate\nand the solution usage. We conducted 20 experiments using the same substrate in the\nsame solution for preparing the freestanding PbZrO membranes. The results show that\n3\nthese ion by-products and chemical side reactions do not have a significant impact on\nthe experimental results, and the substrates (Fig. R4) and the prepared membranes (Fig.\nR5) still maintain the high quality. Considering the reviewer’s suggestion, we have\nadded this part in the revised manuscript.\nFigure R4. Structure characterizations of the STO substrates used 20 times. (a) XRD patterns\nof the STO substrates and the substrates used 20 times. (b) XRD patterns of the STO/LNO/PZO\nand the substrates used 20 times. (c) Corresponding optical microscopic images of the STO\nsubstrate before (I) and after being used 20 times (II).\nFigure R5. Structure characterizations of the PZO thin films on the new STO substrates or\nthe STO substrates used 20 times. (a) XRD patterns of the PZO thin films on the new STO\nsubstrates or the STO substrates used 20 times. (b) Corresponding optical microscopic images of\nthe PZO thin films on the new STO substrates (I) or the STO substrates used 20 times (II).\nreaction rate without generating new redox reactions. The decomposition of water into\nhydrogen and oxygen will act an additional reaction. There is a side reaction in the\npositive electrode, which will produce hydrogen ions, conducive to accelerating the\ndecomposition of the sacrificial layer. And there are no solid by-products.”\n6. While a large-scale film is shown, there’s limited data on spatial homogeneity\nor yield statistics. Was uniformity (thickness, crystallinity) across the 12-inch film\nevaluated comprehensively (e.g., mapping or statistical analysis)?\nResponse: Thank you for your helpful suggestion. We apologize for the issue regarding\nthe uniformity testing of the 12-inch freestanding film. We have examined the\nuniformity of the 12-inch freestanding film. The XRD results from 9 random areas\nindicate that the intensity and width of the diffraction peaks at all positions are similar,\nrevealing that the thickness and crystallinity have not changed significantly and are\nrelatively uniform (Fig. R6). In addition, the 12-inch freestanding film was remarkably\nintact and flat by the optical microscopic image, although minor bubbles were observed\n(Extended Data Fig. 26d). This may be attributed to the uneven PDMS paste process,\nwhich could be removed in the further optimized process. Furthermore, the leakage\ncurrent in the random regions remained at the same level (similar to that of the film\nbefore stripping), which further demonstrated the uniformity of the freestanding film.\nThe detailed information about the leakage current can be found in the response to\nQuestion 4.\nFigure R6. Structure characterizations of the freestanding 12-inch film. (a) Optical photos of\nthe 12-inch sample preparation process and optical photo of the complete 12-inch freestanding\nPZO film. (b) XRD patterns of the freestanding 12-inch film from 9 random areas.\nLine 455-458 in the revised manuscript: “The XRD results from 9 random areas\nindicate that the freestanding film have outstanding uniformity and homogeneity, as\n8\ntheir diffraction intensities are comparable (Extended Data Fig. 27).”\nPage 24 in the revised supporting information: “Extended Data Fig. 27 Structure\ncharacterizations of the freestanding 12-inch film. (a) Optical photos of the 12-inch\nsample preparation process and optical photo of the complete 12-inch freestanding\nPZO film. (b) XRD patterns of the freestanding 12-inch film from 9 random areas.”\n7. The manuscript mentions reuse but lacks experimental data on reusability or\nlong-term process stability: How many times can the process be repeated on the same\nsubstrate without loss of performance?\nResponse: Thank you for your helpful question. Just as we responded in Question 5,\nwe used a new SrTiO substrate to investigate the reproducibility of the preparation\n3\nprocess. After 20 repetitions of the experiment, both the substrate and the fabricated\nfilm exhibited uniform properties. Therefore, according to our method, the substrate\nhas at least 20 cycles of recyclability. The number of recyclable cycles for the substrate\nwith the HCl-etched La Sr MnO sacrificial layer is only one due to the insoluble\n0.7 0.3 3\nMnO particles [Annalen der Physik 534, 2200084 (2022)]. While for the substrate with\n2\nthe water-soluble c-S A O , the number of recyclable cycles without secondary\n3 2 6\ntreatment is less than 5 times [Adv. Mater. 36, 2402419 (2024); Adv. Mater. Inter. 10,\n2202111 (2023)]. This is the advantage of the rapid decomposition brought about by\nDED, which significantly reduces the contact time between the substrate and the\ncorrosive acid solution. We measured the ferroelectric hysteresis loops of freestanding\nfilms that are stripped off from the substrate after 20 uses (Fig. R7). The results showed\nthat the ferroelectric property of the freestanding film did not deteriorate due to the\nrepeated use of the substrate.\nFigure R7. Ferroelectric hysteresis loops of freestanding PZO thin films. (a) Freestanding film\nobtained from the new substrates. (b) Freestanding film obtained from the substrates used 20\ntimes.\nLine 415-417 in the revised manuscript: “Such substrate can be repeated dozens\nof times (Extended Data Fig. 20), which is the critical advance for industrial\n9\nproductivity. This phenomenon is not limited to LAO substrates and STO substrates\nalso exhibit the same repeatability.”\nPage 20 in the revised supporting information: “\nExtended Data Fig. 20 Repeated tests on the same substrate. (a) XRD patterns of\nthe STO substrates and the substrates used 20 times. (b) XRD patterns of the\nSTO/LNO/PZO and the substrates used 20 times. (c) XRD patterns of the PZO thin\nfilms on the new STO substrates or the STO substrates used 20 times. (d)\nCorresponding optical microscopic images of the new STO substrate (I), the STO\nsubstrate used 20 times (II), the PZO thin films on the new STO substrates (III), and\nthe STO substrates used 20 times (IV). (e) Ferroelectric hysteresis loop offreestanding\nfilm obtained from the new substrates. (f) Ferroelectric hysteresis loop of freestanding\nfilm obtained from the substrates used 20 times.\n8. What is the detailed electrochemical decomposition pathway of LaNiO in\n3\nacetic acid under an electric field? Are intermediate phases formed during the DED\nprocess (e.g., La-based complexes)? If so, how do they affect the film or etching\ndynamics?\nResponse: Thank you for your valuable question. We believe that the decomposition\nreaction of the LaNiO sacrificial layer under the influence of an electric field is the\n3\nsame as that when it is immersed in acetic acid solution, that is, LaNiO +6CH COOH\n3 3\n= La(CH COO) +Ni(CH COO) +3H O. Among them, due to the effect of the electric\n3 3 3 3 2\nfield, there might be some [La(CH COO) ]3-n complex products, but these products are\n3 n\nall easily soluble in water [Chem. Geol. 1998, 151(1-4): 349-372]. We conduct Raman\nmeasurements on water, saturated La(CH COO) solution, saturated Ni(CH COO)\n3 3 3 3\nsolution, 10% CH COOH solution, the solution obtained after the decomposition of\n3\n3 3\nDED (Fig. R8). The solutions obtained after LaNiO decomposition were used for a\n3\nlong time, and at least 25 decomposition experiments were conducted, respectively.\nTherefore, the concentrations of all the products in the solution are sufficient to reflect\nthe experimental results. The results show that the solution obtained after LaNiO\n3\ndecomposition is almost identical to a 10% CH COOH solution. And no white\n3\nprecipitates were produced (e.g., La(OH) ). Their Raman spectra do not show the\n3\nmetal-CH COO- characteristic peaks at about 929.0 cm-1, which indicates that there are\n3\nno metal-CH COO- complex products present in the solution after the LNO\n3\ndecomposition. Therefore, we believe that although a small amount of the [La(CH\nn\nsolution. This will not have any impact on the target layer, and our characterization of\nthe structure and electrical properties also confirms this (Fig. 4). Considering the\nreviewer’s suggestion, we have added this part in the revised supporting information.\nFigure R8. Raman spectra of different solutions used in the experiment.\nPage 4 in the revised supporting information: “Although a small amount of the\n[La(CH COO) ]3-n complex products might be produced, it will quickly dissolve in the\n3 n\naqueous solution 36. This will not have any impact on the target layer, and our\ncharacterization of the structure and electrical properties also confirms this point.”\n36. S. Deberdt, S. Castet, J.-L. Dandurand, J.-C. Harrichoury, I. Louiset, Experimental\nstudy of La(OH) and Gd(OH) solubilities (25 to 150° C), and La-acetate\n3 3\ncomplexing (25 to 80° C).Chem. Geol. 151, 349-372 (1998). doi: 10.1016/S0009-\n2541(98)00089-8\n9. Does the current density uniform across the entire sample during DED?\nWere\n3D electric field and current flow simulations performed to support the directional\naspect of DED?\nResponse: Thank you for your beneficial question. As you stated, investigating whether\n11\nthe current density in the sacrificial layer is uniform in different directions is a key point\nthat supports DED method. We are very sorry that we did not discuss this aspect. The\ncurrent density in the sample can be considered to be positively correlated with the\ndecomposition rate. As shown in Figures 1g and 2c, we found that the current parallel\nto the decomposition direction along the sample boundary was basically consistent.\nAmong them, the velocities at the two edges were slightly slower (red dotted line in\nFig. R9), which might be due to the boundary effect (for spin-coated samples, the edges\nare thicker, so the current is smaller). However, except for the smaller current at the\nedges, it does not affect the directional control during the decomposition process\n(Extended Data Fig. 4). Considering the reviewer’s suggestion, we have added this part\nin the revised supporting information.\nFigure R9.Optical micrographs of sacrificial layers decomposition via DED\nLine 172-174 in the revised manuscript: “The directional decomposition process\nof the sacrificial layer has a uniform current density, enabling the freestanding\npreparation of thin films with different orientations.”\nPage 10 in the revised supporting information: “The current density in the sample\ncan be considered to be positively correlated with the decomposition rate. As shown in\nFigures 1g and 2c, we found that the current parallel to the decomposition direction\nalong the sample boundary was basically consistent. Among them, the velocities at the\ntwo edges were slightly slower, which might be due to the boundary effect (for spin-\ncoated samples, the edges are thicker, so the current is smaller). However, except for\nthe smaller current at the edges, it does not affect the directional control during the\ndecomposition process.”\n10. How do local variations affect the etch rate or membrane quality? Are there\nvoltage or current thresholds where electrolysis of the solution or breakdown of target\nlayer occurs?\nof the discussion on the voltage threshold. The local variations will not affect the quality\nof the freestanding thin films or the decomposition rate. In our work, the target layers\nprepared by both the magnetron sputtering method (BiFeO , Extended Data Fig. 15)\n3\nand the chemical solution deposition (PbZrO or SrTiO , Fig. 4 or Extended Data Fig.\n3 3\n16) can all achieve high-quality exfoliation, and the decomposition rate of the LNO\nsacrificial layer is comparable. However, we use different voltages to achieve the\nstripping of different target layers, such as 1 V for BiFeO and 25 V for PbZrO . This\n3 3\nis because high voltage can cause damage to the insulating target films that are low.\nWhen preparing the freestanding BiFeO thin films using a voltage of 25 V, the target\n3 3 3\nbe fabricated at 25 V. For the BiFeO target layer, its voltage threshold should be 5 V.\nbut slower at lower voltages. The minimum decomposition voltage, which is also the\nthreshold voltage, is between 100 pV and 10 pV (Fig. R10).The LNO sacrificial layer\nremains stable for 200 s at 10 pV and will not be electric-decomposed when the voltage\nis below 100 pV. When the voltage is 100 pV, the resistance of the LNO sacrificial layer\ndecreased rapidly within 30 s and did not fully decompose until 600 s later. Considering\nthe reviewer’s suggestion, we have added this part in the revised Methods section.\nFigure R10. Determining voltage threshold of the LNO sacrificial layer of 2 nm through the\ncurrent-time curve.\nPage 4 in the revised supporting information: “Acetic acid solution (10%) was\nselected as the dissolve solution, and the decomposition time was tested respectively at\nthe range with 0.1 A and the voltage with 0.1 V, 2 V, 5 V, 10 V and 25 V, respectively.\nThe voltage thresholds of different target layers may be related to their insulation\nproperties, such as 25 V for PZO and 5 V for BFO. The voltage threshold of the LNO\n13\nsacrificial layer of 2 nm is determined to be between 10 and 100 pV.”\n11. Are local strain variations mapped (e.g., via TEM or synchrotron\nmicrodiffraction) before and after stripping to understand relaxation behavior? Is the\nobserved enhancement in Bader charge supported by in situ experimental validation,\nsuch as electrochemical impedance spectroscopy (EIS) or Raman under bias?\nResponse: Thank you for your valuable suggestion. In fact, the synchrotron-based\nRSM has already exhibited a slight relaxation phenomenon for the target films (Fig.\n4aIII, Extended Data Fig. 12aIII, and Extended Data Fig. 12bIII). We have conducted\nHAADF-STEM mapping on the PZO films before and after stripping, and analyzed the\nlocal strain variations of these films using geometric phase analysis (GPA), a method\nthat combines real-space and fourier-space information to estimate the spatial\ndistribution of strains (Fig. R11). The results show that the PZO thin film before\nstripping experience a greater tensile strain along the in-plane direction, which indicates\nthe slight strain relaxation. And the strains experienced before and after the stripping\nprocess are relatively uniform, and no concentrated defect areas with concentrated\nstrains are found. Considering the reviewer’s suggestion, we have added this part in the\nrevised supporting information. In addition, Bader charge analysis is a charge\noccupancy analysis method based on quantum chemical calculations. Its core lies in\ndetermining the charge distribution of atoms in molecules or crystals through\ntheoretical calculations (such as density functional theory). Essentially, it is the result\nof theoretical simulation rather than a physical quantity directly measured through\nexperiments. Although the electrochemical impedance spectroscopy or Raman under\nbias can to some extent reflect the charge changes in the sample, it is very difficult to\nmake a one-to-one correspondence with the Bader charge of a certain element [Phys.\nRev. B 2011, 83(6): 064107]. In future research, we will continue to explore how to\nestablish a connection between the Bader charge in theoretical calculations and\nexperimental aspects.Once again, we would like to thank the reviewer #1 for the helpful\nquestions, which have enabled us to think further. In this work, we quantitatively\ndemonstrate that the charge transfer between La ions and acetate molecule is enhanced\nin the presence of an electric field, which indicates the internal reason for the\naccelerated decomposition rate.\nbefore and after stripping. (a) Before stripping. (b) After stripping.\nLine 367-369 in the revised manuscript: “This alteration may arise from structural\ndistortion following strain release, a finding that aligns with the results of RSM and\ngeometric phase analysis (GPA) (Extended Data Fig. 17).”\nPage 4-5 in the revised supporting information: “Bader charge analysis is a charge\noccupancy analysis method based on quantum chemical calculations. Its core lies in\ndetermining the charge distribution of atoms in molecules or crystals through\ntheoretical calculations (such as DFT). Essentially, it is the result of theoretical\nsimulation rather than a physical quantity directly measured through experiments.”\nPage 17 in the revised supporting information: “Extended Data Fig. 17 HAADF-\nSTEM images and corresponding GAP analysis of the PZO thin films before and\nafter stripping. (a) Before stripping. (b) After stripping.The results show that the PZO\nthin film before stripping experience a greater tensile strain along the in-plane direction,\nwhich indicates the slight strain relaxation. And the strains experienced before and after\nthe stripping process are relatively uniform, and no concentrated defect areas with\nconcentrated strains are found.”\nReviewer #2 (Remarks to the Author):\nThis manuscript by Li et al. reports a novel technique for preparing freestanding\nmembranes of perovskite-type dielectric materials with preferential crystal orientation,\nnamed DED. I, the reviewer, recognized that the technique proposed in the present\nmanuscript is unique and will be useful for manufacturing thin-film devices coupled\nwith freestanding membranes and versatile substrates or wafers of non-perovskite type\nmaterials. However, I also felt that the manuscript tends to report the experimental\nresults of DED, but insufficient explanation for its basic mechanism. Also, I hardly\nfound any applicability for the research concept of using PZ films (60 nm thick) as a\n15\ntarget of DED, as well as the quality or physical properties of the resulting thin-film\ndevices.\nIn the present state, I that we cannot accept the manuscript for the publication of\nthe present manuscript on Nature Communications as it is because it has never provided\nreasonable evidence (both of experimentally and theoretically) sufficient for certifying\nthe author’s proposal. If the authors would like to release their achievement,\nfundamental revision with extreme reconstruction will be required for data, explanation,\nand discussion in the present manuscript, where the submission to any other journal\n(e.g., Scientific Reports) can be one realistic choice for some situations.\nResponse: Thank you for your comments. Your constructive suggestions have been\nvery helpful in improving our content. We have provided additional experimental data\nto support each of the points used to modify your proposal. Furthermore, we need to\nclarify some points for the reference of the editor and other reviewers.\nFirstly, we are grateful to the reviewer #2 for recognizing the novelty and\nuniqueness of the DED technology. Secondly, the freestanding PbZrO films with 60\n3\nnm are merely one example of the high-quality freestanding films obtained through\nDED method. The main theme of this article is to obtain large-area, multi-type and\nmulti-functional freestanding oxide films with crack-free and wrinkle-free through\nadvanced DED technology. Lastly, we envision the possibility of achieving the\nstripping of all ferroelectric oxide functional films by regulating the resistivity between\ndifferent layers and using different decomposition solutions.\n1. Comments on DED\n(1) Concept as well as experimental results are significantly interesting. However,\nthere is almost no explanation for basic mechanism of the chemical reaction. chemical\nformulae should be proposed in the main document, at least, to clarify the reaction\nscheme in the actual system.\nResponse: Thank you for your valuable suggestion. We are very sorry that we did not\ninclude the chemical reaction equations in the manuscript text. The electric field\naccelerates the LaNiO +6CH COOH = La(CH COO) +Ni(CH COO) +3H O chemical\n3 3 3 3 3 3 2\nreactions, which is a slow spontaneous decomposition process during the immersion\nprocess. The electric field has driven a significant increase in the preparation efficiency\nof functional oxide freestanding membranes, but no new redox reaction was generated.\nUnder the action of electric field, the CH COOH electrolyte obtains the power to\n3\novercome the interface friction, and can move rapidly and directionally, and decompose\nthe sacrificial layer quickly, which effectively improve the characteristics of the solid-\nliquid interface and overcome the resistance caused by surface tension. In this process,\n16\nthe decomposition of water into hydrogen and oxygen will act as an additional\nelectrolytic reaction (2H O(l)→2H (g)+O (g)). In addition, first-principles calculations\n2 2 2\nindicate that the electric field will enhance the affinity of the acetate molecule and the\nLa ions (Fig. 3a). This indicates that La3+ is mainly involved in the decomposition\nreaction, and it is difficult to lose electrons and participate in redox reaction. The salt\ncompounds produced by this reaction will quickly dissolve back into the water, which\nis the main reason why we omitted the acetate ion in the chemical reaction equation of\nfigure 1e originally. However, after re-evaluation, we conclude that the acetate ion\ncannot be omitted. According to the DFT, it can be known that under the influence of\nthe electric field, there is electron transfer and combination between the acetate ion and\nthe La ion (Fig. 3c). This indicates that the formation of acetate lanthanum is a\nnecessary process. Considering the reviewer’s suggestion, we have re-updated the\nchemical reaction equation and included it in the text of the manuscript.\nLine 142-148 in the revised manuscript: “The LaNiO +6CH COOH =\n3 3\nLa(CH COO) + Ni(CH COO) +3H O chemical reactions will take place, subsequently,\n3 3 3 3 2\nthe salt substances will re-dissolve in the solution. The electric field only accelerates\nthe reaction rate without generating new redox reactions. The decomposition of water\ninto hydrogen and oxygen will act an additional reaction. There is a side reaction in the\npositive electrode, which will produce hydrogen ions, conducive to accelerating the\ndecomposition of the sacrificial layer. And there are no solid by-products.”\nLine 181-185 in the revised manuscript: “\n(d) Schematic illustration of the DED process of the LNO sacrificial layer. The DED\nsetup utilized in this study comprises a power supply and a carbon electrode paired with\na positive PDMS/film/LNO/substrate assembly. (e) Schematic depiction of the DED\nmechanism for the LNO sacrificial layer.”\n(2) The reaction scheme described in Fig. 1d and 1e are totally not valid. If the\nanode (i.e., positively-charged electrode) oxidize the H O to form H+, it requires\n2\nthreshold voltage (theoretically > 1.23 V, practically > 2 V) and significant reaction\nwon’t occur under lower voltage (e.g., 0.1 V in Fig. 2a). Moreover, if the reaction\nscheme is true, the reaction will occur without weak acid (i.e., acetic acid) because H+\n17\nwill deliver from H O independent of the concentration of acids. Reference experiment\n2\nwithout weak acid should be performed to certify the reaction scheme, as well as\nverification experiments to confirm the threshold voltage of redox reactions.\nResponse: Thank you for your helpful question. Your question has enabled us to further\nreflect on the DED method itself. Firstly, it is necessary to clarify that we believe there\nare two reactions in the DED process, namely LaNiO +6CH COOH = La(CH COO)\n3 3 3 3\nelectrification\n+Ni(CH COO) +3H O (I) and 2H O H ↑+O ↑(II). Among them, the\n3 3 2 2 2 2\nreaction I is the main reaction. According to the first-principles calculation, LNO\ntransfers 0.8270 electrons to the acetic acid radical when there is no electric field, and\n0.8712 electrons to the acetic acid radical when there is an electric field (Fig. 3c). The\nelectric field increases the transfer of electrons from La atoms to the acetate molecule.\nThis suggests that the electric field can facilitate the exchange between LNO and acid\nions in the solvent, thereby accelerating the decomposition process of LNO. Therefore,\nthe electric field accelerates the LaNiO +6H+ = La3++Ni3++3H O chemical reactions,\n3 2\nwhich is a slow spontaneous decomposition process during the immersion process. The\nformation of acetate lanthanum is a necessary process and the chemical reaction will\ncorrect to reaction I from LaNiO +6H+ = La3++Ni3++3H O. Subsequently, the salt\n3 2\nsubstances (La(CH COO) or Ni(CH COO) ) will re-dissolve in the solution. In\n3 3 3 3\naddition, the reaction II is a secondary reaction and occurs only at higher voltages (Fig.\nR12). We used pure water to decompose the LaNiO sacrificial layer. When the electric\n3\nfield voltage is 2 V, the sacrificial layer does not decompose. When the electric field\nvoltage is 25 V, the sacrificial layer undergoes a decomposition reaction, but the\ndecomposition rate is much lower than that of the decomposition using acetic acid\nsolution. This is in perfect agreement with the description provided by the reviewer,\nnamely that when using pure water, the threshold for the reaction to occur should be\nhigher than 2 V. And the sacrifice layer may undergo decomposition at 3 V.However,\nexcessively high voltage can cause damage to the target layer, which is due to the\nbreakdown of the electric field. This is also the reason why we use a 1 V electric field\nvoltage to obtain the freestanding BiFeO membranes.\n3\nSecondly, we have found that the decomposition reaction of the sacrificial layer\ncan also be carried out using a salt solution (Fig. R13a). This is because a small amount\nof hydrolysis occurs in the acetate ions within the solution. Under the influence of an\nelectric field, the exchange of acetate ions in the acid and the electrons of the LaNiO\n3\nsacrificial layer is enhanced, which further promotes the occurrence of hydrolysis.\nUnder an electric field voltage of 10 V, the sacrificial layer that did not cover the target\nlayer completely decomposed after 50 s. Lastly, we obtained the voltage threshold of\nthe LNO sacrificial layer through the current-time curves, which is 100 pV (Fig. R13b).\nThe LNO sacrificial layer will not be electric-decomposed when the voltage is below\n100 pV. When the voltage is 100 pV, the resistance of the LNO sacrificial layer\ndecreased rapidly within 30 s and did not fully decompose until 600 s later. At this point,\nreaction I is the dominant one because the voltage is much lower than 2 V. Considering\nthe reviewer’s suggestion, we have added this part in the revised manuscript and revised\nsupporting information.\nFigure R13. (a) Decomposition reaction using CH COONa solution in DED process. (b)\nPage 4 in the revised supporting information: “Acetic acid solution (10%) was\nselected as the dissolve solution, and the decomposition time was tested respectively at\n19\nthe range with 0.1 A and the voltage with 0.1 V, 2 V, 5 V, 10 V and 25 V, respectively.\nThe voltage thresholds of different target layers may be related to their insulation\nproperties, such as 25 V for PZO and 5 V for BFO. The voltage threshold of the LNO\nsacrificial layer of 2 nm is determined to be between 10 and 100 pV. ”\nLine Page 7 in the revised supporting information: “\n3. Outlook for DED\nApart from acetic acid solution, we can also use acetic acid salt solution\n(CH COONa solution) or water in the DED method to decompose the LNO sacrificial\n3\nlayer.”\n(3) For confirming the versatility of DED, it should be applied for piezoelectric\n(or dielectric) membranes with various thickness.\nResponse: Thank you for your helpful question. Just as you have described the\nunderlying meaning, the universality of the DED method is of great importance. In fact,\nwe have already obtained different target layers with different thickness using DED\nmethod, such as PbZrO (60 nm, Fig. 4), BiFeO (120 nm, Extended Data Fig. 15)\n3 3\nand\nSrTiO (140 nm, Extended Data Fig. 16). In addition, we re-prepared freestanding\n3 3\nverify the universality of the DED method (Fig. R14). Similar to the 3-inch LaAlO\n3\nsubstrate, the out-of-plane crystal surface of PbZrO on the LaAlO substrate exhibit\n3 3\n(240) and (004) planes due to the different matching methods [Phys. Rev. B 88, 180102\n(2013)]. All the suspended PbZrO membranes with thicknesses of 20 nm, 60 nm, 120\n3\nnm and 180 nm are successfully prepared.\nFigure R14. XRD patterns of PZO membranes with different thicknesses\nLine 340-341 in the revised manuscript: “The PZO freestanding membrane\nexhibits flat and unbroken (Fig. 4a-IV, V) and the thickness can be controlled (Extended\nData Fig. 14).”\npatterns of PZO membranes with different thicknesses.”\n2. Comments on PZ\n(1) At first, I understand that we will not fabricate PZ films by following the\ninstruction in the supporting information (1.2 PbZrO ). Please read the description\n3\nagain carefully to check typographical or technical errors included in the explanation.\nResponse: We are very sorry for the mistake in the description of the preparation of\nPbZrO film. We have now revised this part.\n1.2 PbZrO\n3 2\nnitrate pentahydrate (Zr(NO ) ·5H O, aladdin, 99.9%) is dissolved in 2-\n3 4 2\nMethoxyethanol (C H O , aladdin, 99.5%), There was 10% too much lead. Then, the\n3 8 2\nmixed solvent was heated and stirred on a 75 ℃ hot platform for 2 hours to obtain a\ntransparent precursor solution. Finally, the solvent is left to stand at room temperature\nfor filtration.”\n(2) Totally I could not find any applicability or reasonability for introducing PZ in\nthis research: Pb(Zr,Ti)O or PbTiO should be utilized as ferroelectric layers if we aim\n3 3\nto focus on piezoelectric devices, in general. Research plan using PZ rather than PZT\nand PT is significantly unreasonable and unrealistic from the viewpoint of device\nfabrication.\nResponse: Thank you for your comment. However, we have different opinions. Firstly,\nPbTiO and Pb(Zr,Ti)O , PbZrO are all excellent ferroelectric or antiferroelectric\n3 3 3\nmaterials. Although typical antiferroelectric PbZrO has poor piezoelectric properties,\n3\nthere have been many recent reports on the ferroelectric phase transition and high\npiezoelectricity of PbZrO [Appl. Phys. Rev. 10, 021405 (2023); Small 21, 2410260\n3\n(2025); Nat. Commun. 16, 4263 (2025)], which has expanded its application scope. And\nour results show that the separated PbZrO has a tendency to undergo ferroelectric\n3\ntransformation, indicating that it is a coexistence of ferroelectric and antiferroelectric\nphases. This is an important mechanism for generating highpiezoelectricity. Secondly,\nthe freestanding PbZrO membranes exhibits excellent flexibility and bending strain\n3\n[Nat. Commun. 15, 4414 (2024)], which supports its applications in flexible\nantiferroelectric or ferroelectric fields. In any case, it is unreasonable to evaluate the\nPbZrO material as impractical in ferroelectric or piezoelectric research. Lastly, what\n3\nwe need to further emphasize is that PbZrO is only used as an example of the DED\n3\nmethod. This paper is not limited to PbZrO materials. We have developed a new\n3\n21\nmethod, DED, which can be used to produce a variety of flexible electronic materials\nin multiple functions and across various fields, such as PbZrO , BiFeO , SrTiO and\n3 3 3\nYMnO .They cover a wide range of 3.69 - 4.21 Å in terms of lattice structure as well\n3\nas the fields of ferromagnetism, ferroelectric and dielectrics. In addition, a record-\nbreaking 12-inch polycrystalline membrane has been developed through DED method\nto address the requirements of industrial-scale semiconductor manufacturing. In fact,\nusing the DED method, we can also achieve the preparation of freestanding\nPbZr Ti O (PZT) films (Fig. R15).\n0.52 0.48 3\nFigure R15. XRD patterns of PZT films before and after stripping.\n(3) Even if the author would like to realize ferroelectric (or non-antiferroelectric)\nPZ films in DED process, the experimental results shown in the manuscript did not\nwork efficiently for supporting the author’s concept. P-E loops (in Fig. 4e and 4g) are\nso-called “leaky” which includes high-level current conduction, that prevent the\nmeasurement of adequate switching current to identify their character (ferroelectric or\nantiferroelectric); the identification of FE and AF shall be based on the shape of\nsaturated P-E loop, not only on the switching current.\nResponse: Thank you for your comment. Our aim is not to obtain freestanding PbZrO\n3\nmembranes with ferroelectric properties through DED method, but rather that the\nfreestanding PbZrO membranes obtained through DED exhibit more outstanding\n3\nferroelectric properties than those before stripping.\nFor this phenomenon, we conducted an in-depth analysis using methods such as\nHAADF-STEM, ferroelectric loops and PFM. The “leakage” type ferroelectric\nhysteresis loop mentioned by the Reviewer #2 was not presented in Fig. 4e and 4g. A\nhigh-level current conduction means resistance behavior [Adv. Theory Simul. 3,\n2000106 (2020)], so a circular ferroelectric hysteresis loop can be integrated, while the\ncurrent loop presents an ohmic form. Overall, the ferroelectric hysteresis loops and the\nswitching current indicate that the leakage current in this case is not very significant. It\n22\nis worth noting that the ferroelectric hysteresis loops are the integral of the switching\ncurrent loops over the duration of the applied voltage (P = I(t) dt).This means that\nA\nwhen the current reaches its peak, the polarization is at its lo∫cal minimum value at that\npoint, so, the double ferroelectric hysteresis loops were observed in the antiferroelectric\nmaterials with four switching current peaks. In conclusion, the double ferroelectric\nhysteresis loop is determined by the number of switching current peaks. Therefore, it is\nreasonable to judge the FE/AFE behavior based on the number of switching current\npeaks.\nThere current have been reports on the antiferroelectric-to-ferroelectric transition\nin the PbZrO system. Zhang et al. claimed that by introducing uniform local disorder,\n3\nthe antiferroelectric hysteresis loop transformed into a ferroelectric hysteresis loop\n[Acta Mater. 294, 121085 (2025)]. Jiang et al. showed the ferrielectric-like dipole\nconfiguration but distinct from antiferroelectricity [Nano Lett.23, 1522-1529 (2023)].\nAll of these demonstrate the process of the four-switching peaks transforming into\ndouble-switching peaks.\nIn fact, this process has already been observed during our measurement process\n(Fig. R16). Before the stripping process, the PbZrO thin films still maintained the\n3\nantiferroelectricity of four-switching peaks (Fig. R16a). Its ferroelectric hysteresis\nloops do not show a distinct double hysteresis loop. This may be because it contains the\ncoexistence of some ferroelectric nano-domains. We believe that before stripping, the\nferroelectric/anti-ferroelectric order in the PbZrO film was already coupled and existed,\n3\nsupporting incomplete ferroelectric behavior. After stripping, the PbZrO thin films\n3\nexhibit the phenomenon of peak merging, especially under the high electric fields (Fig.\nR16b). This is sufficient to demonstrate the transformation from anti-ferroelectric\ndomains to ferroelectric domains. Hence, the ferroelectric phase takes the dominant\nposition, and STEM, FFT, and PFM all confirm this, supporting the rationality of our\njudgment. Considering the reviewer’s comment, we have already cited the references.\nFigure R16. Switching current loops of PZO thin films before and after stripping\nthe switching current curve confirm the antiferroelectric property of the as-grown film\n34, 35.”\n34.Y. Zhang, X. Zhang, Z. Zheng, J. Xie, J. Lou, J. Qin, et al. Artificial ferroelectric-\nlike hysteresis in antiferroelectrics with non-uniform disorder. Acta Mater. 294,\n121085 (2025). doi: 10.1016/j.actamat.2025.121085\n35.R.-J. Jiang, Y. Cao, W.-R. Geng, M.-X. Zhu, Y.-L. Tang, Y.-L. Zhu, Y. Wang, F. Gong,\nS.-Z. Liu, Y.-T. Chen, J. Liu, N. Liu, J.-H. Wang, X.-D. Lv, S.-J. Chen, X.-L. Ma,\nAtomic insight into the successive antiferroelectric–ferroelectric phase transition in\nantiferroelectric oxides. Nano Lett.23, 1522-1529 (2023). doi: 10.1021/acs.nanolett.\n2c04972\n(4) Thicknesses of the ferroelectric layer (60 nm) is generally unreasonable for\npiezoelectric application. It can be a major reason for insufficient quality of the PZ films\nwhich causes leakage current conduction. Thicker layers above 100 nm should be\nconsidered for the application of piezoelectric sensors or actuators.\nResponse: Thank you for your comment. We have not found any reports indicating that\nthe 60 nm ferroelectric film lacks good applicability. In fact, not only the thin films with\n60 nm, but also thinner films have interesting applications. For example, the pure\nantiferroelectric phase has been stabilized in a PbZrO film with a thickness of 9 nm\n3\n[Nat Commun 16, 6536 (2025)], the BiFeO film with a thickness of 30 nm due to the\n3\nsubstrate strain has the highest remanent polarization value [Phys. Rev. Lett. 107,\n147602 (2011)], in single-layer BiFeO , which breaks through the critical size effect,\n3\nan astonishingly stable ferroelectricity has been introduced [Nature 570, 87-90 (2019)],\nand giant electromechanical effect and piezoelectric response have been found in\nHf Zr O films with 55 nm [ACS Appl. Mater. Interfaces 16, 975-984 (2023)]. These\n0.5 0.5 2\nresults indicate that not only thick films but also other thickness have ferroelectric and\npiezoelectric applications. In conclusion, it is sufficient to ensure that the present film\nhas a high-quality level to limit the generation of leakage current.\nIn addition, in the ferroelectric hysteresis loops we obtained, there is no high\nleakage current as described by Reviewer #2. The leakage currents of the PbZrO thin\n3\nfilms before and after stripping are less than 1×10-8 A/cm2 (Fig. R17). The traditional\npiezoelectric applications may require a thicker structure. However, in the flexible\npiezoelectric devices after peeling, thinner films are more easily bent, which is\nbeneficial for generating piezoelectric and flexoelectric effects. Moreover, our results\nalso show that it has a good discrimination in the arm bending test, which can be used\nfor bending sensing tests. Therefore, the thinner film has unique advantages in\n24\nflexibility, high sensitivity, high flexibility and fast response. Finally, it is important to\nnote that the 60 nm freestanding PbZrO film is merely an example in our work. We\n3\ncan fabricate various types, different thicknesses and a wide range of perovskite\nmembranes using the DED method. We also prepared films with a thickness of 100 nm\nand above (Extended Data Fig. 15 and Extended Data Fig. 16). In future research, we\nwill conduct a comparison of the piezoelectric properties.\nFigure R17. Leakage current test of PZO thin films. (a) Leakage current curve of PZO thin\nfilms before stripping. (b) Leakage current curve of PZO thin films after stripping.\n(5) If the authors would like to discuss the ferroelectricity of PZ from theoretical\nviewpoint, detailed explanation and discussion should be shown in the main document,\nnot only in the supporting information. I hardly agree with the author’s claim for the\ncrystal symmetry which is explained by data in Figs. 4b and 4c because of the lack of\nexplanation and discussion, as well as poor resolution of figure images.\nResponse: Thank you for your comment. We do not quite understand the question\nraised by Reviewer #2. Because the ferroelectric/antiferroelectric structural transition\nof PbZrO has been fully covered in the main text rather than being presented as\n3\nsupporting information. Moreover, the description of poor image resolution is\nsubjective. It is worth noting that we have indeed observed a structural transition from\na 1/4 super-diffraction point to a 1/3 super-diffraction point (Fig. 4b-III and Fig. 4c-III).\nThis structural transformation has also been studied in recent research [Nat. Commun.\n15, 3438 (2024); Nature 637, 1104-1110 (2025); Nat Commun15, 4414 (2024)],\nindicating that PbZrO undergoes a transition from typical antiferroelectric domains to\n3\nferroelectric-like domains. We calculated the out-of-plane lattice constants, and found\nthat the initial PbZrO film has a period of 4 pseudo-cubic cells while the stripped film\n3\nhas a period of 3 pseudo-cubic cells, which further confirmed the structural phase\ntransition (Fig. 4b-IV and 4c-IV). Furthermore, we made a local magnification of\nfigures 4b-II and 4c-II. It can be observed that the polarization direction of the initial\nPbZrO film is , while that of the stripped PbZrO film is , which further\n3 3\n25\nindicates that the crystal symmetry has changed (Fig. R18).\nFigure R18. Atomic vector displacement diagram. (a) Initial films. (b) Freestanding films.\n(6) PFM data is not sufficient for certifying the piezoelectric character of the\nresulting films. The measurement of strain - electric field (S-E) curves is favorable to\nconfirming that it will not be electrostrictive strain or not, and then to determine the\npiezoelectric constants for evaluating the device performance.\nResponse: Thank you for your comment. We have provided the local phase loops (Fig.\nR19a) and butterfly curves (Fig. R19b) of the freestanding PbZrO films by PFM.\nconsecutive cycles of cyclic electric fields, the ferroelectric switching (about 180\ndegrees) and piezoelectric deformation (about 0.6 nm) of the freestanding PbZrO films\n3\nremain almost unchanged. This result indicates that it has an outstanding piezoelectric\nproperty. Furthermore, the static piezoelectric coefficient of the freestanding PbZrO\n3\nfilms is calculated to be about 80 pm/V (Fig. R19c), which is comparable to the BFO\nfilm with 180 nm. [J. Appl. Phys.110, 084102 (2011)]. Although this value is relatively\nlow, we still obtain a considerable response value in the application even in the within\nthe 3-inch freestanding film (Fig. 5e).\nWe believe that the macroscopic signals (a wide range of signal recognition from\n3 mV to 24 mV) of the array can more clearly represent the piezoelectric properties of\nthe freestanding PbZrO films and its applicability of deformation sensor applicability.\nsupporting information for verifying the piezoelectric property of the freestanding film.\nIn addition, we need to reemphasize that our work does not specifically refer to\npiezoelectric freestanding PbZrO films. This is merely one of the various materials that\n3\nwill be available in the future. We cannot list all the results together.\nphase loops. (b) Localbutterfly curves. (c) Piezoelectric coefficient-voltage loop.\nLine 436-437 in the revised manuscript: “In addition, the above results are also\nconfirmed by local piezoelectric signals (Extended Data Fig. 25).”\nPage 23 in the revised supporting information: “\nExtended Data Fig. 20 Local ferroelectricity and piezoelectricity of freestanding\nPZO films. (a) Local phase loops. (b) Local butterfly curves. (c) Piezoelectric\ncoefficient-voltage loop.”\n(7) Performance of the piezoelectric membrane is significantly important when it\nis compared with the competitive devices, i.e., piezoelectric sensors using ferroelectric\npolymers such as a PVDF which can be formed by low-temperature deposition process:\nthe device concept shall be reconsidered if the performance of PZ membrane is\ncomparable or inferior to the polymer-based ferroelectrics.\nResponse: Thank you for your comment. As you said, the PVDF polymer material has\ngood piezoelectric properties. Especially when combined with the ferroelectric BaTiO ,\n3\nit can exhibit unparalleled piezoelectricity [ACS Appl. Mater. Interfaces 14, 17849-\n17857 (2022);Adv. Funct. Mater. 32, 2108496 (2022)].However, in previous studies,\nit was difficult to obtain a completely freestanding oxide functional film with wrinkle-\nfree and crack-free with through the water-soluble Sr Al O sacrificial layer [Nature\n3 2 6\nMater15, 1255-1260 (2016); Nature 570, 87-90 (2019); Adv. Sci. 11, 2307571 (2024)].\nAlthough the findings of T-Sr Al O have to some extent addressed this issue [Science\n4 2 7\n383, 388-394 (2024)], the results in subsequent studies do not seem to be particularly\nsignificant [Adv. Mater. 36, 2307682 (2024); Adv. Mater. 36, 2402916 (2024)]. Here,\nwe have developed a new approach, the DED method, for obtaining large-area, high-\nquality freestanding oxide functional films. The maximum area can reach 12-inches,\nand the ultra-high decomposition speed effectively solves the problem of damage to the\ntarget layer.This is precisely the main argument of this article. The concerns raised by\nthe reviewer #2 should no longer be about the mutual comparison of individual\nmaterials, but rather about further integration and development. Furthermore, it seems\nthat oxide functional films, such as NaNbO films [Science 369, 292-297 (2020);\n(2018)]. This is less than the piezoelectric signal with 24 mV shown by our PbZrO\n3\nfilms (Extended Data Fig. 22). In fact, we have already been conducting relevant\nresearch and making preparations for the giant piezoelectric freestanding films. The\nfreestanding PbZrO film is just one example in our work. Even its sensor application\n3\nis only one aspect. We believe that the preparation of large-area, multi-functional\nfreestanding oxide films with various properties will provide support for sensors, chip\nintegration and flexible materials.\n(8) I am wondering that the description of “distinct 180°. domain switching (Fig.\n4f)” is adequate or not from the viewpoint of domain engineering, which is related to\nthe existence or non-existence of tilted domain structure (e.g., 109° and 71° domains\nfor epitaxial BFO films). Detailed discussion based on the crystal symmetry of PZ (as\nwell as its crystal orientation or domain structure) should be included.\nResponse: Thank you for your comment. As far as we know, the description of 180°\ndomain switching is reasonable, and it depends on the phase structure of the material.\nFor the BiFeO -based materials of the rhombic phase, 109° or 71° domains are the main\n3\ndirections for domain switching [Appl. Phys. Lett. 119, 132901 (2021)]. And for the\ncubic (pseudo-cubic), tetragonal, and orthorhombic phase, 90° or 180° domains are the\nmain directions for domain switching [Nano Lett. 15, 6506-6513 (2015); J. Appl. Phys.\n128, 184103 (2020)]. Although Gao et al. believe that the ferroelectric behavior of\nPbZrO stems from the orthorhombic-to-tetragonal phase transition in the Pb-rich\n3\nsystem [Chem. Mater. 29, 6544-6551 (2017)], the low formation energy ferroelectric\northorhombic phase has also been proposed and is being studied [Phys. Rev. B\n105,125409 (2022)]. Taking into account the actual PFM data of the local box-in-box\nphase images (Fig. 4f) and local phase loops (Fig. R19a) support, we believe that the\nfreestanding PbZrO film is an orthorhombic ferroelectric phase. Therefore, we have\n3\ndecided to retain the original description. Considering the reviewer’s suggestion, we\nhave cited this new reference.\nLine 378-379 in the revised manuscript: “In contrast, the freestanding PZO film\nexhibits distinct 180° domain switching (Fig. 4f) 33, indicative of a transition towards\nferroelectric properties.”\n33.R. G. Burkovsky, G. A. Lityagin, A. E. Ganzha, A. F. Vakulenko, R. Gao, A.\nDasgupta, B. Xu, A. V. Filimonov, L. W. Martin, Field-induced heterophase state in\nPbZrO thin films. Phys. Rev. B 105, 125409 (2022). doi: 10.1103/PhysRevB.\n3\n105.125409\n(9) Again, it looks significantly hard to accept the concept for applying PZ in the\n28\npresent manuscript because it does not support the author’s proposal.\nResponse: Thank you for your comment. Here, it should be emphasized that the\nanalysis of the PZO film's properties is entirely reasonable, and the flexible\npiezoelectric performance can also be applied. The signals already have\ndistinguishability. Our data have already demonstrated the outstanding piezoelectric\nproperties of freestanding PbZrO films, but this is not all. Furthermore, we will once\n3\nagain emphasize the main idea of this paper, which is to propose a new sacrificial layer\nof LaNiO and its DED method. Based on this sacrificial layer and the DED method, a\n3\nvariety of multifunctional and multi-scale freestanding oxide functional films have been\nrealized. The freestanding PbZrO film that the Reviewer #2 was concerned about is\n3\njust one example. In fact, we have already been able to fabricate freestanding films\nusing materials, such as PbZrO , PbTiO , PbZr Ti O , BiFeO , SrTiO , YMnO ,\n3 3 0.52 0.48 3 3 3 3\nLa Sr MnO , SrRuO , and BiSmFe O (BSFO), among others. We have extended\n0.7 0.3 3 3 2 6\nour method to another system. We have successfully prepared the freestanding films of\nBiSmFe O double-perovskites and we have developed by DED method (Fig. R20) [Sci.\n2 6\nAdv. 11, eads4925 (2025)], ensuring the structural stability of the orthorhombic double-\nperovskites. Further development of semiconductor device fabrication and large-scale\nproduction will facilitate the industrialization of freestanding oxide films.\nFigure Redacted\nFigure R20. Schematic diagram of freestanding BSFO double-perovskite film\n3. Comments on other materials\n(1) It looks unfair that the ferroelectric properties of BFO membrane was evaluated\nonly by SGH data. P-E measurement shall be performed as similarly to other materials\nbecause it includes the evaluation for the quality of BFO membranes (e.g.,\nmicrostructural cracks or defects which is hardly evaluated by SGH manner).\nResponse: Thank you for your comment. In fact, it is reasonable to indicate the\nferroelectric enhancement of the freestanding BFO film through SHG. The SHG\nintensity (I) is related to the light-induced nonlinear polarization (P) in the following\nway: I∝|P|2 [Nat. Commun. 14, 2274 (2023)]. In our work, the SHG intensity has\nincreased by approximately double (Extended Data Fig. 18a), which clearly indicates\nthe enhancement of ferroelectricity in the freestanding BiFeO film. Taking into account\n3\nthe Reviewer #2 doubts about the quality of the freestanding BFO films. We have\npresented the leakage current curves and ferroelectric hysteresis loops of freestanding\nBFO films. The leakage current of the BFO film before and after the stripping process\nis almost the same, which clearly indicates that the freestanding film has high quality\n(Fig. R21a-b). The ferroelectric hysteresis loops also show an about twofold increase\n29\nin the remanent polarization, supporting the SHG results (Fig. R21c-d). Considering\nthe reviewer’s suggestion, we have added this part in the revised manuscript.\nFigure R21. Leakage current curves and ferroelectric hysteresis loops of BFO film before\nand after stripping. (a, b) Leakage current curves. (c, d) Ferroelectric hysteresis loops.\nLine 391-393 in the revised manuscript: “Furthermore, the BFO freestanding film\nexhibits enhanced ferroelectric properties and structural transformation after transfer\nand the STO film shows high flatness, crystallinity, and excellent dielectric\nperformance (Extended Data Fig. 18-19).”\nPage 6 in the revised supporting information: “The SHG intensity (I) is related to\nthe light-induced nonlinear polarization (P) in the following way: I∝ |P|239.”\nPage 18-19 in the revised supporting information: “\nExtended Data Fig. 19 Leakage current curves and ferroelectric hysteresis loops\nof BFO film before and after stripping. (a, b) Leakage current curves. (c, d)\nFerroelectric hysteresis loops.\nThe leakage current of the BFO film before and after the stripping process is almost the\nsame, which clearly indicates that the freestanding film has high quality (Extended Data\nFig. 19a-b). The ferroelectric hysteresis loops also show an about twofold increase in\nthe remanent polarization, supporting the SHG results (Extended Data Fig. 19c-d).\n39.S. Xu, J. Wang, P. Chen, K. Jin, C. Ma, S. Wu, E. Guo, C. Ge, C. Wang, X. Xu, H.\nYao, J. Wang, D. Xie, X. Wang, K. Chang, X. Bai, G. Yang Magnetoelectric coupling\nin multiferroics probed by optical second harmonic generation. Nat. Commun. 14,\n30\n2274 (2023). doi: 10.1038/s41467-023-38055-x\n(2) Dielectric constant of STO films (k = 67.1, in Extended Data Fig. 15b) is\nsignificantly lower than conventional data (typically k > 100). Quality of STO\nmembranes should be evaluated, as well as BFO membranes.\nResponse: Thank you for your comment.As pointed out by Reviewer #2, the dielectric\nconstant of SrTiO usually exceeding 100 should refer to the bulk SrTiO [J. Appl. Phys.\n3 3\n43, 2124 (1972)]. However, in the SrTiO thin film, its dielectric constant (maybe lower\n3\nthan 60) is simultaneously influenced by defects, the preparation method, and the\nmeasurement method [Appl. Phys. Lett. 91, 062910 (2007)]. The effective dielectric\nconstant is precisely the crucial evidence that demonstrates its function [Nature 443,\n679-682 (2006)]. As far as we know, the effective dielectric constant of the SrTiO film\n3\nis at most about 100, and the breakdown field is 7 MV/cm [Nature 605, 262-267 (2022)].\nIt is only manifested in the freestanding SrTiO films. In our work, the dielectric\n3\nconstant we have presented is the effective dielectric constant, as it takes into account\nthe combined effect of all the layers in the SrTiO and its devices. Moreover, a\n3\nbreakdown field of about 15 MV/cm represents the current highest standard, which\nfurther confirms the high quality of the SrTiO films. The high breakdown strength of\n3\ndielectric materials are the essential performance parameters that are related to the\ndevice power consumption and reliability [Nat. Electron. 2, 563-571 (2019)]. These\nresults all support what we have emphasized, that the freestanding films obtained\nthrough the DED method possess high quality and applicability in the field of electronic\ndevices and their storage.\n4. Comments on manuscript document\nThe present manuscript still includes typographical errors or misinformation in the\nmain document as well as supporting information. Document check (spelling &\ngrammar) in a more careful manner will be required.\nResponse: Thank you for pointing out the grammar and typographical errors. And we\nare very sorry for our grammar errors and unreadable description, and we have rectified\nthese mistakes in the revised manuscript and marked them in blue. For example:\nLine 45-46 in the revised manuscript: “The strain-relaxed PbZrO membranes\n3\nexhibit the hysteresis loop of the antiferroelectric transition to ferroelectric.”\nLine 72-74 in the revised manuscript: “The etching process would generate narrow\ngaps, typically ranging nanometers, which are significantly smaller than the micron-\nscale wetting angle of the decomposition solution.”\nLine 157-158 in the revised manuscript: “The decomposition rate was evaluated\nby monitoring the intensity of the characteristic absorption peak of the sacrificial layer.”\nbetween the magnitude of the applied voltage and the decomposition rate of the\nsacrificial layer. This observation underscores the facilitative role of the electric field\nand holds significant potential for enabling the future efficient fabrication of large-scale\nfreestanding oxide membranes.”\nReviewer #3 (Remarks to the Author):\nThe authors describe a novel methodology for creating freestanding crystalline\nmembranes that utilizes electrochemically drive decomposition of sacrificial etching\nlayers with higher electrical conductivity than the desired membrane layers. This\ndirectional electrodynamic decomposition (DED) method shows improvement over\nother chemical etch release processes in the etch rates that can be achieved, the\nthickness of sacrificial layers that can be used, and the flatness of the resulting\nmembranes. The authors present examples of successful membrane separation, post-\nseparation characterization to verify membrane quality, and an etching mechanism that\nis supported by DFT calculations. This work represents a remarkable technical\nachievement that will be of interest throughout the oxide semiconductor community\nand industry.\nResponse: Thank you very much for appreciating the content of our manuscript, and\nyour constructive suggestions have been a great help in improving our content.\n1. The authors describe some limitations to the materials for which this technique\ncan be applied including chemical compatibility and lattice matching. However, the\napplicability of the technique is driven in part by the difference in conductivity between\nthe membrane layer and the sacrificial layer (here LaNiO ). The manuscript would\n3\nbenefit from a quantitative discussion of difference in conductivity of the layers needed\nfor the DED method to be effective and/or some commentary on how the etch processes\nparameters may need to be adjusted as the conductivity of the layers approach one\nanother.\nResponse: Thank you for your valuable suggestion. As you said, the applicability of\nthe technique is driven in part by the difference in conductivity between the membrane\nlayer and the sacrificial layer. This is precisely one of the tasks we are currently\nundertaking, which is to make the conductive materials La Sr MnO or SrRuO\n0.7 0.3 3 3\nflexible and capable of being stripped off (Fig. R22a). In fact, these materials were\npreviously used as sacrificial layers [Nature 626, 529-534 (2024); Sci. Adv. 7, eabh1284\n(2021)]. In our work, they can not only serve as sacrificial layers but also can be stripped\ndue to the difference in resistivity. These findings undoubtedly expand the application\nscope of DED method, supporting their application of electron spin [Nat. Commun. 15,\n32\n5975 (2024); Phys. Rev. Lett.96, 145504 (2006)]. In addition, when the insulation\nproperties of the target layer and the sacrificial layer become consistent, using different\nsolution can be employed to adjust their stripping properties. For instance, the use of\nNaCl solution enables the exfoliation of LaNiO by employing the La Sr MnO\n3 0.7 0.3 3\nsacrificial layer, which is due to the occurrence of the MnO +H O+4NaCl→\n2 2\nMnCl +Cl +4NaOH (power-on conditions) reaction resulting in the different\n2 2\ndecomposition rate (Fig. R22b) [Annalen der Physik 534, 2200084 (2022)].\nFigure Redacted\nFigure R22.Progress of the stripping experiments of other systems. (a) XRD patterns of\nfreestanding LSMO films before and after stripping. (b) Electrodynamic decomposition of LNO\nand LSMO sacrificial layers in NaCl solution at a working voltage of 10 V.\nWe have presented all the materials described in the manuscript as well as some\nof the resistance values of the prospective materials for reference (Table R1). Under the\nconditions described in the manuscript (10% acetic acid solution and LaNiO sacrificial\n3\nlayer), they all achieved complete stripping due to the high resistance (greater than 100\nOhm). Considering the reviewer’s suggestion, we have added this part in the revised\nmanuscript.\nTable R1. Materials described in the work as well as some of the resistance values of the\nprospective materials.\nLine 345-347 in the revised manuscript: “The stripping of the target layer is\nachievable so long as its resistance exceeds that of the LNO sacrificial layer.”\nPage 26 in the revised supporting information: “\nExtended Data Table 2 Materials described in the work as well as some of the\nresistance values of the prospective materials.\nUnder the conditions described in the manuscript (10% acetic acid solution and\nLNO sacrificial layer), they all achieved complete stripping due to the high resistance.\n45.T. Hara, T. Ishiguro, K. Shinozaki. Oxygen-concentration-dependent electrical\n33\nresistances of SrTiO -based thin films. Jpn. J. Appl. Phys. 49, 041104 (2010). doi:\n3\n10.1143/JJAP.49.041104\n46.S. Sugumaran, T. A. Divya, R. K. Sivaraman, C. S. Bellan, K. C. Sekhar, M. F.\nJamlos, Structure, morphology and I-V characteristics of thermally evaporated\nLaAlO nanostructured thin films. J. Mater. Sci.-Mater. El. 33, 9085-9100 (2022).\n3\ndoi: 10.1007/s10854-021-07139-z\n47.A. Bogusz, D. Bürger, I. Skorupa, O. G. Schmidt, H. Schmidt, Bipolar resistive\nswitching in YMnO /Nb:SrTiO pn-heterojunctions. Nanotechnology 27, 455201\n3 3\n(2016). doi: 10.1088/0957-4484/27/45/455201\n48. H. Li, J. Tu, G. Xi, X. Liu, X. Liu, S. Du, D. Lu, D. Zu, Y. Zhang, Q. Wang, D.\nZheng, X. Zhang, J. Tian, L. Zhang, Large ferroelectricity in Hf Ce O\n0.85 0.15 2-δ\npolycrystalline thin films via lattice expansion. Inorg. Chem. Front. 11, 7535-7544\n(2024). doi: 10.1039/D4QI01558D\n2. This reviewer believes this work should be published with a few additional\ncomments about the applicability and limitations of the DED method.\nResponse: We sincerely appreciate your recognition of this study and are very grateful\nfor your valuable comments and suggestions regarding the applicability and limitations\nof the DED method. Below is a detailed response to the questions you raised:\nYour comment on applicability has prompted us to conduct further reflection.\nAlthough we can obtain a series of high-quality freestanding oxide functional films via\nthe DED method, this method still has certain limitations: 1. The sacrificial layer needs\nto be conductive in order to generate energy consumption. 2.The insulation layer of the\ntarget layer needs to be higher than the sacrificial layer. 3.The target layer needs to be\nrelatively stable.\nTaking the LNO sacrificial layer in an acetic acid (10%) decomposition solution\nas an example, the target layer to be stripped must meet one of the following conditions:\n1. The target layer has higher electrical insulation than LNO. 2. The target layer itself\nhas extremely high chemical stability. Alternatively, the decomposition solution can be\nreplaced with other types of solutions, which requires further relevant research.\nMoreover, compared with the traditional chemical soaking method, DED method\noffers several advantages: 1. It is fast and enables large-area stripping; 2. It is\ncontrollable, with the stripping direction, voltage, and current all adjustable for different\nsacrificial and target layers; 3. By selecting the appropriate electrolyte solution, it can\nbe adapted to various scenarios. For instance: 1. the use of NaCl solution enables the\nexfoliation of LaNiO by employing the La Sr MnO sacrificial layer. 2. La-Ni-based\n3 0.7 0.3 3\nmaterials are excellent superconducting materials [Nature 634, 579-584 (2024);\ndoi.org/10.1038/d41586-025-00450-3], but their poor insulation makes exfoliation\n34\ndifficult. This issue can be addressed by selecting an appropriate solution.\nLine Page 7 in the revised supporting information: “\n3. Outlook for DED\nTaking the LNO sacrificial layer as an example, the target layer to be exfoliated\nmust meet one of the following conditions (restriction):\n1. It has higher insulation than LNO.\n2. It itself exhibits extremely high chemical stability.\nCompared with the traditional chemical soaking method, DED method offers\nseveral advantages:\n1. It is fast and enables large-area stripping.\n2. It is controllable, with the stripping direction, voltage, and current all adjustable\nfor different sacrificial and target layers.\n3. By selecting the appropriate electrolyte solution, it can be adapted to various\nscenarios. For instance: 1. the use of NaCl solution enables the exfoliation of LNO by\nemploying the La Sr MnO sacrificial layer. 2. La-Ni-based materials are excellent\n0.7 0.3 3\nsuperconducting materials, but their poor insulation makes exfoliation difficult. This\nissue can be addressed by selecting an appropriate solution. Apart from acetic acid\nsolution, we can also use acetic acid salt solution (CH COONa solution) or water in the\nMany thanks,\nWith best regards,\nSincerely yours.\nLinxing Zhang, Xianran Xing\nUniversity of Science and Technology Beijing\nBeijing 100083, China\nE-mail address: linxingzhang@ustb.edu.cn, xing@ustb.edu.cn\n35"}, {"round": 2, "reviewer_comments": {"reviewer_1": "I recommend that the revised manuscript, “Efficient electrodynamic stripping for 12-inch wafer-scale freestanding ferroelectric oxide membranes,” be accepted for publication in Nature Communications, as the authors have addressed all substantive comments.", "reviewer_2": "I appreciate for enormous comments and data from the authors which will be of significant help for explaining the importance of the present research more intensively. Here I prepared some additional comments (below) which have been considered after reading the revised manuscript with comments on author's response. Some major issues, mainly related to DED mechanism and piezoelectric materials (PZ), shall be revised for publication.\n[As for the response on \"1. Comments on DED\"]\nResponse 1-(1) and 1-(2):\nOK. We thank that the authors provide additional data and explanation to clarify the reaction schemes for chemical decomposition of LaNiO3 sacrificial layers and H2O media under voltage application.\nLaNiO3 + 6 CH3COOH = La(CH3COO)3 + Ni(CH3COO)3 + 3 H2O\nIf the authors would utilize the formula (above) as an irreversible reaction, we recommend replacing the \"= (equals)\" symbol to \"→ (single arrow, to left)\" symbol, similarly to the scheme of water splitting in Fig. 1. Or, if as a reversible reaction, replace to \"? (double allows, to left and right)\" The symbol \"=\" is basically utilized only for the thermodynamical equation.\nAnd then, we appreciate if you clarify the state of matter for respective chemical species (i.e., ions or molecules), e.g.\nLaNiO3 (s) + 6 CH3COOH aq → La3+ aq + Ni3+ aq + 3 CH3COO- aq + 3 H2O (l),\nor any other candidates like\nLaNiO3 (s) + 6 CH3COOH aq → La(CH3COO)3 (s or aq ) + Ni(CH3COO)3 (s or aq) + 3 H2O (l).\nResponse 1-(3):\nOK. New additional data for the XRD results on different thickness is just suitable for our request to confirm the versatility of DED.\n[As for the response on \"2. Comments on PZ\"]\nResponse 2-(1):\nOK. We expect that the procedure is valid to prepare the chemical solution for PZ coating.\nResponse 2-(5):\nOK. I appreciate for additive data of magnified image with color guidance (circles and arrows). I have missed some essential information for the crystal symmetry in the previous version.\nResponse 2-(6):\nOK. Additional data in Fig. R19 is more favorable for explaining the piezoelectric character of the resulting film.\nResponse 2-(7):\nThe opinion (i.e., comments of \"Response:\" from the authors) shall be reflected clearly to the main document of the revised manuscript.\nResponse 2-(8):\nOK.\nResponse 2-(2),(3),(4),(9)\nI understand the author's viewpoint that the freestanding is just one example and then the author’s group aim to extend their research to other materials. And then, I confirmed the piezoelectric property of the resulting PZ film (60 nm).\nIn Response 2-(4), the authors might be confused for the difference in \"piezoelectric\" application and \"ferroelectric\" application. Some major factors for the piezoelectric application are ruled by the layer thickness of membrane (e.g., maximum displacement, which often determines the net length for the displacement in the piezoelectric membrane or the sensor resolution against variable forces on piezoelectric pressure meters)[Nguyen et al., Scientific Reports, 7. 12915 (2017), etc.], as well as by the size effects that mainly affect on the ultra-thin films typically below ~1000 nm.[Kerry et el., Phys. Rev. Mater., 4, 024407 (2020)./Nguyen et al., Sens. Actuators A Phys., 199, 98 (2013). /Marauska et al., Mycrosyst. Technol. 18, 787 (2012)./etc.]\nThe BFO film shown in the reference [Ji et al., Nature, 570, 87 (2019).] will not utilized for practical piezoelectric sensors directly because it accepts the net displacement only up to ~50 pm. Giant electromechanical effect by HZO membrane [Guvelna et al., ACS Appl. Mater. Interfaces, 16, 975 (2024)] were accomplished by the coupling of the unique piezoelectric effect in HZO (i.e., the inverse size effects) and the asymmetric shape of the membrane, where the situation is significantly apart from the author's works.\nWe ask additional data on piezoelectric response (same as for Fig. R19) for a series of PZ films with different thickness (i.e., samples in Fig. R14) to clarify the validity of the film thickness.\n[As for the response on \"3. Comments on other materials\"]\nResponse 3-(1):\nOK. Additional data (i.e., I-V and P-E curves) will prove satisfactory for discussion the ferroelectricity of the resulting films.\nResponse 3-(2):\nThe opinion (i.e., comments of \"Response:\" from the authors) shall be reflected clearly to the main document of the revised manuscript.\n[As for the response on \"4. Comments on manuscript document\"]\nOK.\nEOT", "reviewer_3": "The authors have addressed all this reviewer's concerns in their revisions. I recommend the manuscript for publication."}, "author_response": "Response Letter\nDear Reviewers,\nThe authors highly appreciate the reviewing and the reviewers’ comments on our\nmanuscript entitled “Efficient electrodynamic stripping for 12-inch wafer-scale\nfreestanding ferroelectric oxide membranes” (NCOMMS-25-33496A). The comments\nand suggestions are all valuable and very helpful for revising and improving the quality\nof the manuscript. We have revised the manuscript point by point according to the\ncomments of the reviewers. The revised text was marked as a blue highlighted font in\nthe manuscript or supporting information. We believe that the present revised\nmanuscript is more coherent and articulate after the revisions. The detailed corrections\nare listed as follows.\nReviewer #1 (Remarks to the Author):\nI recommend that the revised manuscript, “Efficient electrodynamic stripping for\n12-inch wafer-scale freestanding ferroelectric oxide membranes,” be accepted for\npublication in Nature Communications, as the authors have addressed all substantive\ncomments.\nResponse: We thank the Reviewer for acknowledging the significance of this work.\nReviewer #2 (Remarks to the Author):\nI appreciate for enormous comments and data from the authors which will be of\nsignificant help for explaining the importance of the present research more intensively.\nHere I prepared some additional comments (below) which have been considered after\nreading the revised manuscript with comments on author’s response. Some major issues,\nmainly related to DED mechanism and piezoelectric materials (PZ), shall be revised for\npublication.\nResponse: Thank you very much for appreciating the content of our manuscript, and\nyour constructive suggestions have been a great help in improving our content. More\ndetails have been supplemented and answered one by one in the following replies.\n[As for the response on “1. Comments on DED”]\nResponse 1-(1) and 1-(2):\n1. OK. We thank that the authors provide additional data and explanation to clarify\nthe reaction schemes for chemical decomposition of LaNiO sacrificial layers and H O\n3 2\nmedia under voltage application.\nLaNiO + 6CH COOH = La(CH COO) + Ni(CH COO) + 3H O\n3 3 3 3 3 3 2\nIf the authors would utilize the formula (above) as an irreversible reaction, we\n1\nrecommend replacing the “= (equals)” symbol to “→ (single arrow, to left)” symbol,\nsimilarly to the scheme of water splitting in Fig. 1. Or, if as a reversible reaction, replace\nto “⇌ (double allows, to left and right)” The symbol “=” is basically utilized only for\nthe thermodynamical equation.\nAnd then, we appreciate if you clarify the state of matter for respective chemical species\n(i.e., ions or molecules), e.g.\nLaNiO (s) + 6CH COOH (aq) → La3+ (aq) + Ni3+ (aq) + 3CH COO- (aq) + 3H O (l)\n3 3 3 2\nor any other candidates like\nLaNiO (s) + 6CH COOH (aq) → La(CH COO) (s or aq) + Ni(CH COO) (s or aq)\n3 3 3 3 3 3\n+ 3H O (l)\nmore than willing to accept this, and it was something that was lacking in our previous\nmanuscript version. The electric field accelerates the LaNiO (s)+6CH COOH (aq) →\n3 3\nLa(CH COO) (s or aq)+Ni(CH COO) (s or aq)+3H O (l) chemical reactions, which\n3 3 3 3 2\nis a slow spontaneous decomposition process during the immersion process. Just as we\ndescribed in our previous response, the formation of salt (La(CH COO) or\n3 3\nNi(CH COO) ) is inevitable and we should view it as a two-step process consisting of\n3 3\nreaction and dissolution. Therefore, we did not cancel out the acetate ions before and\nafter the reaction in the equation, and we also took into account the existence states of\neach substance. Considering the reviewer’s suggestion, we have made adjustments to\nthis part in the revised manuscript.\nLine 143-145 in the revised manuscript: “The LaNiO (s)+6CH COOH (aq) →\n3 3\nLa(CH COO) (s or aq)+Ni(CH COO) (s or aq)+3H O (l) chemical reactions will take\n3 3 3 3 2\nplace, subsequently, the salt substances will re-dissolve in the solution.\nResponse 1-(3):\n2. OK. New additional data for the XRD results on different thickness is just\nsuitable for our request to confirm the versatility of DED.\nResponse: Thank you for your efforts in enriching our manuscript’s dataset.\n[As for the response on “2. Comments on PZ”]\nResponse 2-(1):\n3. OK. We expect that the procedure is valid to prepare the chemical solution for\nPZ coating.\nResponse: Thank you for your acceptance of our revisions in this section.\nResponse 2-(5):\n4. OK. I appreciate for additive data of magnified image with color guidance\n(circles and arrows). I have missed some essential information for the crystal symmetry\n2\nin the previous version.\nResponse: Thank you for your acceptance of our revisions of additive data of magnified\nimage with color guidance (circles and arrows).\nResponse 2-(6):\n5. OK. Additional data in Fig. R19 is more favorable for explaining the\npiezoelectric character of the resulting film.\nResponse: Thank you for your acceptance of the additional data we provided regarding\nthe local piezoelectric properties of freestanding PbZrO films, including the local\n3\nphase loops and butterfly curves.\nResponse 2-(7):\n6. The opinion (i.e., comments of “Response:” from the authors) shall be reflected\nclearly to the main document of the revised manuscript.\nResponse: Thank you for your suggestion. We have included some of the responses in\nthe main text. The main content is about the comparison of the piezoelectric properties\nof PVDF and freestanding PbZrO films.\nproduced a robust 24 mV signal, while the edge area generated a significantly weaker\n5 mV signal. These values are superior to the piezoelectric signal of about 4.29 mV/%\nshown in the polyvinylidene fluoride 49.”\n49. C.-M. Wu, M.-H. Chou, W.-Y. Zeng, Piezoelectric response of aligned electrospun\npolyvinylidene fluoride/carbon nanotube nanofibrous membranes. Nanomaterials 8,\n420 (2018). doi.org/10.3390/nano8060420\nResponse 2-(8):\n7. OK.\nResponse: Thank you for your acceptance of our description regarding ferroelectric\ndomains.\nResponse 2-(2),(3),(4),(9)\n8. I understand the author’s viewpoint that the freestanding is just one example\nand then the author’s group aim to extend their research to other materials. And then,\nI confirmed the piezoelectric property of the resulting PZ film (60 nm).\nIn Response 2-(4), the authors might be confused for the difference in\n“piezoelectric” application and “ferroelectric” application. Some major factors for the\npiezoelectric application are ruled by the layer thickness of membrane (e.g., maximum\ndisplacement, which often determines the net length for the displacement in the\npiezoelectric membrane or the sensor resolution against variable forces on piezoelectric\n3\npressure meters) [Nguyen et al., Scientific Reports, 7. 12915 (2017), etc.], as well as by\nthe size effects that mainly affect on the ultra-thin films typically below ~1000 nm.\n[Kerry et el., Phys. Rev. Mater., 4, 024407 (2020). Nguyen et al., Sens. Actuators A\nPhys., 199, 98 (2013). Marauska et al., Mycrosyst. Technol. 18, 787 (2012). etc.]\nThe BFO film shown in the reference [Ji et al., Nature, 570, 87 (2019)] will not\nutilized for practical piezoelectric sensors directly because it accepts the net\ndisplacement only up to ~50 pm. Giant electromechanical effect by HZO membrane\n[Guvelna et al., ACS Appl. Mater. Interfaces, 16, 975 (2024)] were accomplished by the\ncoupling of the unique piezoelectric effect in HZO (i.e., the inverse size effects) and the\nasymmetric shape of the membrane, where the situation is significantly apart from the\nauthor’s works.\nWe ask additional data on piezoelectric response (same as for Fig. R19) for a series\nof PZ films with different thickness (i.e., samples in Fig. R14) to clarify the validity of\nthe film thickness.\nResponse: Thank you for your comment and suggestion. First, we wish to convey our\nappreciation to the reviewers for their endorsement of the core innovation of our work,\na novel method (denoted as DED) for the preparation of freestanding oxide films.\nThrough this DED method, a range of applicable freestanding oxide films can be\nobtained, featuring various types, multifunctional characteristics, and large dimensions.\nA portion of the research on this method has been presented in this paper.\nSecond, we understand the limitations imposed by the maximum displacement and\nsize effects pointed out by the reviewers regarding the application of thinner films.\nHowever, the transformation of the phase structure and the regulation of the micro-area\nstructure also have a significant impact on the piezoelectric properties of the\npiezoelectric/ ferroelectric film [Nat. Mater. (2025), doi.org/10.1038/s41563-025-\n02354-z; Nature 633(8031), 798-803 (2024)]. This is precisely the viewpoint we put\nforward in the paper, that is, the series of phase transition processes that occur when the\nPZO film is peeled off is the reason why the film exhibits significant piezoelectricity\n(Fig. 4). In our future work, we will conduct further in-depth research on the\npiezoelectric properties of ferroelectric films.\nLastly, we provide data on the local piezoelectric properties of PZO freestanding\nfilms across different thicknesses (Fig. R1). Consistent with the reviewers’ viewpoint,\nfilm piezoelectricity decreases as thickness reduces. Nevertheless, all PZO freestanding\nfilms across thicknesses showed distinct piezoelectric signals, peaking at ~ 80 pm/V\n(0.08 nm/V). Even at a thickness of 20 nm, a static piezoelectric constant of ~ 40 pm/V\n(0.04 nm/V) was retained. Notably, the piezoelectric signals for all film with different\nthicknesses were obtained from freestanding films exfoliated from LaAlO substrates,\n3\n4\nwhich is consistent with the process employed to fabricate the three-inch piezoelectric\nsensor. Considering the reviewer’s suggestion, we have added this part in the revised\nmanuscript and revised supporting information.\nFigure R1. local piezoelectric properties of PZO freestanding films across different thicknesses\nLine 430-433 in the revised manuscript: “The above results are also confirmed by\nlocal piezoelectric signals (Extended Data Fig. 25). Although the piezoelectric\nproperties of the films are limited by the maximum displacement and size effect 53,54,\nthe piezoelectric responses of freestanding PZO films of different thicknesses have been\nconfirmed by PFM (Extended Data Figure 26).”\n53. M. D. Nguyen, E. P. Houwman, G. Rijnders. Large piezoelectric strain with ultra-\nlow strain hysteresis in highly c-axis oriented Pb(Zr Ti )O films with columnar\n0.52 0.48 3\ngrowth on amorphous glass substrates. Sci. Rep. 7, 12915 (2017). doi.org/10.1038/\ns41598-017-13425-w\n54. M. D. Nguyen, M. Dekkers, E. Houwman, R. Steenwelle, X. Wan, A. Roelofs, T.\nSchmitz-Kempen, G. Rijnders, Misfit strain dependence of ferroelectric and\npiezoelectric properties of clamped (001) epitaxial Pb(Zr ,Ti )O thin films.\n0.52 0.48 3\nAppl. Phys. Lett. 99, 252904 (2011). doi.org/10.1063/1.3669527\n[As for the response on “3. Comments on other materials”]\nResponse 3-(1):\n9. OK. Additional data (i.e., I-V and P-E curves) will prove satisfactory for\ndiscussion the ferroelectricity of the resulting films.\nResponse: Thank you for your acceptance of the data we added regarding the\nferroelectric properties of the BiFeO film before and after stripping process.\n10. The opinion (i.e., comments of “Response:” from the authors) shall be\nreflected clearly to the main document of the revised manuscript.\nResponse: Thank you for your suggestion. We have placed the discussion on the\neffective dielectric constant of SrTiO in the revised supporting information.\nfilm exhibits an exceptionally high breakdown resistance field of 15 MV/cm and a high\ndielectric constant of 67.1 (Extended Data Fig. 18b). These properties render the\nfreestanding STO film well-suited for applications in electronic devices. In the STO\nfilm, its dielectric constant is simultaneously influenced by defects, the preparation\nmethod, and the measurement method 50. The effective dielectric constant is precisely\nthe crucial evidence that demonstrates its function. The effective dielectric constant of\nthe STO film is at most about 100, and the breakdown field is 7 MV/cm 51. It is only\nmanifested in the freestanding STO films. In our work, the dielectric constant we have\npresented is the effective dielectric constant, as it takes into account the combined effect\nof all the layers in the STO and its devices. Moreover, a breakdown field of about 15\nMV/cm represents the current highest standard, which further confirms the high quality\nof the STO films. The high breakdown strength of dielectric materials are the essential\nperformance parameters that are related to the device power consumption and reliability\n52.”\n50. J.-H. Ahn, J.-Y. Kim, S.-W. Kang, J.-H. Kim, J.-S. Roh, Increment of dielectric\nproperties of SrTiO thin films by SrO interlayer on Ru bottom electrodes. Appl.\n51. J.-K. Huang, Y. Wan, J. Shi, J. Zhang, Z. Wang, W. Wang, N. Yang, Y. Liu, C.-H.\nLin, X. Guan, L. Hu, Z.-L. Yang, B.-C. Huang, Y.-P. Chiu, J. Yang, V. Tung, D. Wang,\nmembranes as insulators for two-dimensional transistors. Nature 605, 262-267\n(2022). doi.org/10.1038/s41586-022-04588-2\n52. W. Li, J. Zhou, S. Cai, Z. Yu, J. Zhang, N. Fang, T. Li, Y. Wu, T. Chen, X. Xie, H.\nMa, K. Yan, N. Dai, X. Wu, H. Zhao, Z. Wang, D. He, L. Pan, Y. Shi, P. Wang, W.\nChen, K. Nagashio, X. Duan, X. Wang, Uniform and ultrathin high-κ gate dielectrics\nfor two-dimensional electronic devices. Nat. Electron. 2, 563-571 (2019). doi.org/10.\n1038/s41928-019-0334-y\n[As for the response on “4. Comments on manuscript document”]\n11. OK.\nResponse: Thank you for your approval of the grammatical and layout errors we have\ncorrected.\nReviewer #3 (Remarks to the Author):\nThe authors have addressed all this reviewer’s concerns in their revisions. I\nrecommend the manuscript for publication.\nResponse: Thank you for your recognition to our work.\n7"}, {"round": 3, "reviewer_comments": {"reviewer_2": "I recognized that the concept and the contents have been improved significantly on the revised manuscript by kindly providing the additional data and discussion and then that the manuscript can be accepted for publication on the journal. We appreciate the valuable efforts by the author's for answering the questions and requests from the reviewers."}, "author_response": ""}]

Decision letter