ABSTRACT Van der Waals integration of freestanding perovskite-oxide membranes with two-dimensional semiconductors has emerged as a promising strategy for developing high-performance

electronics, such as field-effect transistors. In these innovative field-effect transistors, the oxide membranes have primarily functioned as dielectric layers, yet their great potential for

structural tunability remains largely untapped. Free of epitaxial constraints by the substrate, these freestanding membranes exhibit remarkable structural tunability, providing a unique

material system to achieve huge strain gradients and pronounced flexoelectric effects. Here, by harnessing the excellent structural tunability of PbTiO3 membranes and modulating the

of oxide membranes for utilization in advanced non-volatile electronics and highly sensitive pressure sensors. SIMILAR CONTENT BEING VIEWED BY OTHERS STRAIN-INDUCED ROOM-TEMPERATURE

FERROELECTRICITY IN SRTIO3 MEMBRANES Article Open access 19 June 2020 ULTRAHIGH-POWER-DENSITY FLEXIBLE PIEZOELECTRIC ENERGY HARVESTER BASED ON FREESTANDING FERROELECTRIC OXIDE THIN FILMS

Article Open access 03 April 2025 THE ROLE OF LATTICE DYNAMICS IN FERROELECTRIC SWITCHING Article Open access 02 March 2022 INTRODUCTION Recently, the rich properties and diverse

applications of freestanding oxide membranes have attracted great attention1,2,3. By breaking the chemical bond between films and substrates, oxide membranes exhibit great structural

tunablility, achieving huge strain and strain gradient far exceeding the range which can be reached in bulk materials and epitaxial films3,4,5,6,7. Additionally, the freestanding membranes

can also be freely transferred onto any desired substrates to construct novel interfaces and devices. For example, high-density polar nanodomains8, tunable ferroelectric domain walls9,

ferroelectric tunnel junctions10,11, were demonstrated by integrating ferroelectric membranes with silicon wafers. Excitingly, van der Waals integration of perovskite-oxide membranes and

two-dimensional semiconductors has become a promising strategy to construct high-performance field-effect transistors (FETs)12,13,14, showing a high on/off current ratio, a near-ideal

subthreshold swing value, and more. In these FETs, freestanding oxide membranes have primarily used as dielectric layers due to their excellent dielectric or ferroelectric properties12,13,

yet their remarkable structural tunability remains largely untapped. The great structural tunability in membranes should enable effective mechanical switching of the polarization and

ferroelectric domains via flexoelectric effect, providing promising routes to design novel mechanically-operated electronic devices. Flexoelectricity is an electromechanical coupling between

polarization and strain gradient, which enables the mechanical control of ferroelectric polarization. The flexoelectric effect finds wide applications in flexoelectronics15,16,17, sensing

and actuating18,19, data storage20,21, and energy harvesting22. Although flexoelectric effect is a weak effect of little practical significance in bulk materials, its role can be more

pronounced in thin films23,24,25, especially in freestanding oxide membranes and in van der Waals layered materials26,27,28 due to their remarkable structural tunability, superior elasticity

and flexibility2,3,5. By bending the membranes, giant strain gradients and flexoelectric response has been reported in BiFeO36,29 and ferroelectric 2D material CuInP2S626,27,28,30. However,

whether such pronounced flexoelectric effects can be utilized in realizing low-pressure-mechanical polarization switching and applied in designing non-volatile FeFETs remains to be

explored. In this work, benefiting from the excellent structural tunability of freestanding PbTiO3 membranes and the adjustment of underlying substrate’s elasticity, we achieved ultralow

pressure (down to 0.06 GPa) for mechanical polarization switching. Moreover, as an application demonstration, we developed a prototype non-volatile ferroelectric field-effect transistor

(FeFET) on silicon that can be operated mechanically and electrically for the first time. By constructing freestanding PbTiO3/MoS2 heterostructures, tip-pressure-induced flexoelectric effect

can switch the polarization state in PbTiO3 layer and thus further influence the transport behavior in the MoS2 channel. RESULTS DESIGN FOR LOW-PRESSURE-DRIVEN POLARIZATION SWITCHING To

achieve low-pressure-driven polarization switching, we propose to tune the energy barrier height and potential profile by utilizing the excellent structural tunability in freestanding

membranes and optimizing the elasticity of the underlying substrate. Our experimental design is illustrated in Fig. 1b. In case I, PTO membranes are epitaxially grown on STO substrates,

where the double well (blue line) in the energy profile becomes asymmetric (red line) when incorporating flexoelectricity into Landau free energy28. Thus, the upward polarization state is

destabilized and can be switched to the downward polarization state when the flexoelectric field is strong enough by applying large tip pressure to bend the film and substrate. In case II,

freestanding membranes are released from the original substrate and transferred onto a rigid oxide substrate. In this case, the in-plane lattice parameters (_a_ and _b_) are free to relax

since there is no chemical bonding between the membrane and substrate. As shown in the theoretical calculations (Fig. 1c), allowing relaxation of _a_ and _b_ lattice constants can apparently

lower the polarization switching energy barrier even fixing the switching path to be 180° polarization switching. Effective Hamiltonian calculations also show that this energy barrier can

be further lowered by allowing the polarization in freestanding membranes to tilt and flip to the in-plane direction as an intermediate step31, which means the 180° switching consists of two

90° rotations. In fact, similar two-step polarization switching has been commonly observed in many ferroelectrics, including BiFeO320, Pb(Zr0.2Ti0.8)O332, Pb(Zr0.1Ti0.9)O333, etc. In case

III, we further manipulate the substrate elasticity, by transferring PTO membranes on a softer substrate. Thus, the tip-pressure will cause more obvious deformation in membranes, which leads

to a larger strain gradient and a more pronounced flexoelectric effect. Although the energy barrier height is the same as it is in case II under homogenous strain (blue solid and dotted

lines), a larger strain gradient would cause a more inequivalent energy double-well (red solid and dotted lines), which maximizes the mechanical switching efficiency. Finite-element

simulation (Fig. 1d) shows that vertical flexoelectric field is widely distributed in nearly the entire region beneath the tip in case III, also indicating a more pronounced flexoelectric

effect when transferring membranes on soft substrate. During the FEM calculation, for the epitaxial PTO film (case I), the displacement continuity boundary was adopted due to the strong

covalent bonding in PTO/LNO interfacial layer. the Young’s modulus and the Poisson’s ratio of LNO were set as _E_LNO = 299 GPa34 and _ν_LNO = 0.2734, respectively. For freestanding PTO

membrane (cases II and III), the contact boundary and Coulomb friction model were adopted to simulate the possible sliding at interface. The underlying substrates in cases II and III are LNO

and Au, respectively. The Young’s modulus and the Poisson’s ratio of Au were set as _E_Au = 78 GPa35 and _ν_Au = 0.4235. Details of theoretical calculations can be found in Methods.

EXPERIMENTAL DEMONSTRATION OF ULTRALOW-PRESSURE-INDUCED POLARIZATION SWITCHING By using reactive molecular beam epitaxy, high-quality PTO films were epitaxially grown on (001) SrTiO3 (STO)

substrates with 8 nm thick LaNiO3 (LNO) as a bottom electrode denoted as Epi(27 nm)/LNO(8 nm)/STO. PTO membranes (12, 18, 27 nm) were grown on (001) SrTiO3 (STO) substrates with a Sr3Al2O6

(SAO) sacrificial layer. Subsequently, freestanding PTO membranes were prepared by dissolving SAO and then transferred onto LNO/STO substrates (denoted as FS | | LNO/STO), platinum-coated

silicon substrate (denoted as FS | |Pt/Si) and gold-coated silicon substrate (denoted as FS | |Au/Si). Schematic images of these samples are shown in Fig. 2a. The spring constant and inverse

optical lever sensitivity of AFM tip were calibrated using the force curve and thermal noise method for obtaining the accurate tip force28,36,37,38,39,40. More details about the membrane

growth, transfer, and characterizations can be found in the Methods and Fig. S2. Piezoresponse force microscopy (PFM) measurements demonstrate that both the epitaxial and freestanding PTO

membranes exhibit upward spontaneous polarization. The vertical-PFM (VPFM) phase images of Epi/LNO/STO and FS | |Au/Si are shown in Figs. S3d, h, and the polarization state of the region

polarized with −10 V sample bias is similar to that of the as-grown region, implying that the latter has an upward self-polarization41. During mechanical writing process, the downward

polarization grows gradually at the expense of the upward one with the increasing flexoelectric field with larger mechanical load pressure (Figs. 2b and S4). Here, the scanning mode is used

in our experiments to induce polarization switching by AFM tip. The percentage of the switching area as a function of the tip pressure is shown in Fig. 2c. The threshold tip pressure _P_th

becomes lower in FS||LNO/STO sample (1.83 GPa) than that in Epi/LNO/STO sample (2.14 GPa), which demonstrates that the “freestanding” state indeed lowers the switching barrier since it

enables greater freedom in lattice deformation. As illustrated in Fig. 1, in freestanding membranes, the relaxation of in-plane lattice parameters (_a_ and _b_) can lower the switching

barrier and this energy barrier can be further decreased when polarization is tilted and flipped to in-plane direction as an intermediate step. The two-step switching is confirmed by LPFM

amplitude measurements as shown in Fig. S1. The LPFM amplitude of the data taken under the intermediate pressure shows the maximum value, indicating the polarization is lying along the

in-plane directions. In contrast, the initial (_P_up) and final (_P_down) states exhibit much weaker LPFM amplitudes, which is consistent with the two-step model. Next, we investigate the

effect of substrate elasticity on tip-induced polarization switching. For freestanding membranes transferred to different target substrates, _P_th is significantly different with the lowest

value (0.54 GPa) found in FS||Au/Si sample. Substrate elasticity is a contributing factor to this phenomenon, as the Young’s modulus of LNO, platinum, and gold are 29934, 16842, and 78 

GPa35, respectively. This demonstrates that mechanical polarization switching is more efficient when transferring membranes onto a substrate with the lowest Young’s modulus, which means that

modulating the underlying substrate’s elasticity can enhance the flexoelectric field significantly. To exclude the potential contribution of metal work function43,44,45, we performed

contrast experiments by inserting monolayer MoS2 into the oxide/metal interfaces. As shown in Fig. S5, _P_th in FS | |Au(Pt)/Si and FS | |MoS2/Au(Pt)/Si are the same, thus the existence of

MoS2 barely influences mechanical polarization switching behavior. In addition, the gold thickness dependence of the threshold tip pressure in FS | |Au/Si samples is obviously shown in Fig. 

2d. _P_th decreases with increasing gold thickness and finally reaches its minimum for _d_Au = 100 nm. This is because the overall substrate elasticity decreases with the increasing

thickness of gold coating layer (the Young’s modulus of silicon is 160 GPa46, which is larger than gold) and the Young’s modulus for Au film decreased with increasing film thickness47. This

phenomenon further proves that mechanical writing pressure is affected by the substrate elastic properties other than metal work function. Besides, we also investigated the effect of probe

size on mechanical writing behavior (Fig. S6). Fig. S6a, b show that the _P_th is 2.96 GPa when AFM tip radius is 10 nm, which is much higher than that written by an AFM tip with 25 nm

radius (0.54 GPa). This is mainly due to the highly localized flexoelectric field when the tip radius is 10 nm, which may fail to switch the polarization completely along the thickness

direction of the film, as constrained by the long-range Coulomb interactions between electric dipoles48. Our FEM simulations (Figs. S6c, d) also prove that vertical flexoelectric field is

confined within a small spatial region along the thickness direction (Rtip = 10 nm), however, it is widely distributed into nearly the entire region when the tip radius is 25 nm. We compare

the _P_th in our samples with other ferroelectric perovskite oxide membranes from previous works (Figs. 3a and S7), showing that the required tip pressure is getting lower as the membrane

thickness decreases. Notably, an ultralow switching pressure down to 0.06 GPa is achieved in 12 nm freestanding PTO membranes transferred on gold (100 nm)-coated silicon, which is the lowest

value ever reported36,38,49,50,51,52,53,54, even lower than those with thinner thickness. From the view of device applications, high-quality ultrathin membranes are technically demanding in

fabrication and integration32, thus it will be more attractive to achieve mechanical domain switching in relatively thicker membranes. However, for epitaxial films constrained by hard

substrates, it is challenging to mechanically switch the polarization in thicker films due to the contribution of tip-induced flexoelectricity decreases substantially when the film thickness

is above ~25 nm32,33,38,55. Here, we successfully achieve low switching pressure (0.54 GPa) in 27 nm freestanding PTO membranes transferred on gold (100 nm)-coated silicon (FS(27 

nm)||Au(100 nm)/Si), showing three times smaller than that in epitaxial membrane with the same thickness. Reversible polarization switching can be achieved by mechanical writing and

electrical erasing in FS(27 nm)||Au(100 nm)/Si, as shown in Fig. 3b. The initial downward polarization state (the yellow region) can be switched to the upward state (the violet region) by

applying the negative voltage of −8 V (Fig. 3b, left). Next, this upward polarization poled by electric field can be mechanically written to the downward state (the yellow region) (Fig. 3b,

middle). Then, to test the repeatability, a negative voltage (−8 V) reverses the polarization to upward again (the violet region)(Fig. 3b right). Moreover, the mechanical polarization

switching region is stable and it barely evolves over time (Fig. S8). Scanning kelvin probe force microscopy (SKPFM) is performed to investigate the surface potential of polarization poled

by electricity and loading force (Fig. 3c). Section profiles of the SKPFM images demonstrate that the surface potential of electrically poled region (Δ_E_1) is higher than that by tip

pressure (Δ_E_2), indicating charge injection is inevitable during the electrical switching process36,53. FLEXOELECTRICITY-TUNED FERROELECTRIC FIELD-EFFECT TRANSISTORS Next, we explore

transferrable PTO membranes as a mechanically-tuned ferroelectric gate dielectric for two-dimensional (2D) field-effect transistors, as a preliminary attempt. In ferroelectric field-effect

transistors (FeFETs), the ferroelectric polarization state can be tuned by tip pressure via flexoelectricity and detected by the conductance of the channel material. Meanwhile, 2D materials

such as MoS2 have been widely used as channel materials due to their atomic thickness, absence of dangling bonds, and potentially high mobility56,57. Thus, integrating PTO with MoS2 offers a

promising route for realizing low-power, high-speed operation and reconfigurable functionalities devices. To fabricate MoS2 transistors with PTO bottom-gate dielectrics, we sequentially

transferred PTO, MoS2, and hBN on Au/SiO2/Si substrates (Figs. 4a, b and S9). PTO membrane with a thickness of 27 nm was transferred onto an Au/SiO2/Si substrate. A monolayer MoS2 thin film

grown by chemical vapor deposition (CVD) was then transferred on the top of the freestanding PTO membrane. The shape of the MoS2 channel was then defined by electron beam lithography (EBL)

and subsequent reactive ion etching (RIE). Next, source and drain electrodes (Ti/Au) were deposited at the end of MoS2 channels. Finally, devices were encapsulated by hBN to avoid sample

degradation and more importantly, it can protect MoS2 from damage during mechanically writing. In our experiments, we can effectively avoid electron doping during the fabricating process of

MoS2 transistors. The method of releasing monolayer MoS2 from a sapphire is shown in Fig. S10. Schematic of a bottom-gate MoS2 FET and optical images of the device can be seen in Fig. 4a, b,

respectively. PFM results (Fig. 4c) indicate that the PTO polarization state can be mechanically switched by AFM tip even across hBN and MoS2 layers. Vertical PFM signal of PTO region

covered by MoS2 is obviously weaker than that without MoS2 capping layer (Fig. S11), due to the screening effect of semiconductor MoS258. In addition, a relatively thick hBN layer (13 nm) on

the top of MoS2 also weakens the flexoelectric effect. These might be the reasons for incomplete polarization reversal. In flexoelectricity-tuned MoS2 transistors, the n-type MoS2 channel’s

charge state is controlled by an underlying PTO membrane. Tip-induced flexoelectricity can switch the polarization state of the underlying PTO membrane and then a scanning of the drain

current (_I_D) can read the state of the polarization since different states are associated with distinct transport behaviors. Specifically, the initial polarization state of PTO region

under the channel area is uniformly points upward, which accumulates electrons into MoS2 and the _I_D is in a high current state (‘on’ state). Mechanically switching the polarization of PTO

to _P_down state depletes electrons from MoS2, leading to a low current state of _I_D (‘off’ state). Fig. 4d shows the room temperature drain current (_I_D) vs voltage (_V_DS) relations of

the device, which are obtained when the PTO membrane at initial _P_up state and after mechanical writing to _P_down states at zero back-gate voltage (_V_GS = 0 V), respectively. At _V_DS = 

0.1 V, _I_D is suppressed, changing from 53 pA in the _P_up state to 3.5 pA in the _P_down state, indicating that mechanically-tuned on/off state is achieved effectively in our prototype

FeFET device. DISCUSSION While ultralow pressure mechanical polarization switching has been realized and flexoelectricity-tuned FeFET has been demonstrated, there are still some challenges

to be solved in the near future. At present, for the prototype flexoelectricity-tuned FeFETs, a relatively high mechanical pressure (1.8 GPa) is needed. This is because an encapsulating hBN

with a thickness of up to 13 nm is required to protect the underlying MoS2 due to the poor mechanical durability of the monolayer MoS259. Replacing MoS2 with other suitable 2D channel

materials that have better mechanical properties should lower the required pressure and will be explored in the future. Moreover, reversible polarization switching still relies on a

combination of a mechanical and an electrical switching process so far. Reversible mechanical switching60 has been demonstrated in epitaxial membranes by manipulating the competition between

the flexoelectric field and effective dipolar field delicately61. Following the same mechanism, using a bilayer membrane as the ferroelectric layer, reversible mechanical polarization

switching should be applied in membrane-based FeFETs. In summary, we report an ultralow-pressure-driven polarization switching in freestanding PTO membranes. Without epitaxial constraints,

the greater freedom in lattice deformation lowers the energy barrier for polarization switching. Besides, tip-pressure can be further reduced by tuning the substrate elasticity. Finally, a

prototype non-volatile flexoelectricity-tuned FeFET has been fabricated by integrating PTO with MoS2 and the ‘on’ and ‘off’ states can be controlled by mechanical switching polarization of

the freestanding PTO membrane. Mechanical switching with ultralow pressure can effectively avoid sample damage, and benefit low-energy-consumption and high-sensitivity devices. Our work

demonstrates great potential in combining ferroelectric memebranes with 2D materials for novel electronic applications, and paves the way for stress-modulated devices with low

energy-consumption or high sensitivity. METHODS DENSITY FUNCTIONAL THEORY (DFT) CALCULATIONS The nudged elastic band (NEB) method62,63 is used to estimate the ferroelectric switching energy

barrier, which is implemented in the Vienna ab initio simulation package code64,65. The projected augmented wave method66,67 and the Perdew-Burke-Ernzerhof revised for solids exchange

correlation68 are used in the calculations. The plane-wave cutoff energy is 520 eV and the k-mesh is 9 × 9 × 8. The geometry structure is relaxed until the force on each atom is less than

0.01 eV Å−1, and the energy convergence criterion is 10−7 eV. As for PTO epitaxially grown on STO substrate, PTO in-plane lattice parameters are fixed (_a_ = _b_ = 3.877 Å) and out-of-plane

lattice parameter (_c_) is free to relax. In freestanding membranes, the lattice constants of _a_, _b_, and _c_ are all allowed to relax. THE FLEXOELECTRIC CALCULATIONS The strain and strain

gradient distributions in PTO films were calculated using finite element method (FEM). The model of an AFM tip in contact with a 12 nm-thick PTO film on 100 nm-thick substrates was built

for FEM calculations. The radius of AFM tip was set as 25 nm. A vertical force of 2 μN was applied on the top surface of tip. Different mechanical boundary conditions at interface were

adopted in the epitaxial and freestanding films. For the epitaxial films, the displacement continuity boundary was adopted due to the strong covalent bonding in PTO/LNO interfacial layer.

For the freestanding films on different metal-coated substrates, the contact boundary and Coulomb friction model were adopted to simulate the possible sliding at interface. The Young’s

modulus and Poisson’s ratio of PTO, LNO, Au were set as _E_PTO = 142 GPa69, _E_LNO = 299 GPa34, _E_Au = 78 GPa35, _ν_PTO = 0.2969, _ν_LNO = 0.2734, _ν_Au = 0.4235, respectively. The vertical

flexoelectric field can be calculated as $${E}_{flexo}={f}_{3333}{\varepsilon }_{zz,z}+{f}_{3113}({\varepsilon }_{rr,z}+{\varepsilon }_{\theta \theta,z})+{f}_{3131}{\varepsilon }_{rz,r},$$

(1) where the transverse, longitudinal and shear flexoelectric coupling coefficients were set as _f_3113 = 5 V, _f_3333 = 2 V, _f_3131 = 2 V, respectively70. The flexoelectric field was then

incorporated into the Landau free energy to obtain the double-potential well curves. DEPOSITION OF EPITAXIAL THIN FILMS The water-soluble SAO layer was grown first on (001) STO

single-crystalline substrate followed by the growth of a thin film PTO by reactive MBE system. The SAO films were grown with an oxidant (10% O3 and 90% O2) background partial pressure of

oxygen _p_O2 of 1 × 10−6 Torr and at a substrate temperature _T_substrate = 950°C. The SAO and PTO films were grown layer by layer, for each of which the thickness was monitored by

reflection high-energy electron diffraction (RHEED) oscillations. The PTO films were grown with an oxidant (distilled O3) background pressure of 2×10−5 Torr and at _T_substrate = 625 °C. Due

to the volatility of lead, PTO films were grown in adsorption-controlled mode with a fixed Pb:Ti flux ratio of 13:1 and the thickness was controlled by deposition time of titanium. The

perovskite LaNiO3 (LNO) film were grown first on (001) STO single-crystalline substrate followed by the growth of PTO film. The LNO films were grown on the TiO2-terminated SrTiO3 (001)

substrates by reactive MBE using a DCA R450 MBE system, with the substrate temperature of 600 °C and an oxidant background pressure of 1×10−5 Torr using the distilled ozone. RELEASE AND

TRANSFER PTO FILMS Freestanding PTO films were directly transferred to desired substrate without any mechanical support from polydimethylsiloxane (PDMS) or other tapes during the whole

process, which avoids chemical residue on the film surface. STRUCTURAL CHARACTERIZATION The crystal structure was examined by a high-resolution single-crystal X-ray diffractometer using a

Bruker D8 Discover instrument. The incident X-ray was from Cu-Kα emission and had a wavelength of 1.5418 Å. PIEZORESPONSE FORCE MICROSCOPY MEASUREMENTS The local ferroelectric properties

were measured on freestanding films on a conducting Si wafer using an Asylum Research MFP-3D Origin+ SPM scanning probe microscope. Olympus AC240TM Pt/Ti-coated tip (2 N m−1 in force

constant) were used in the PFM measurements. Hysteresis loops were collected in the dual AC resonance tracking (DART) mode. PFM images were taken in the DART mode with driving voltage (1 V

a.c.) applied at the tip. During the domain writing, the voltage was also applied at the tip. The corresponding pressure can be estimated with a tip radius of 25 nm (Olympus AC240TM) under

the assumption that the tip-sample contact is represented by a disc with radius equivalent to the tip radius36,51,60,71. CVD GROWTH AND TRANSFER OF MONOLAYER MOS2 We grew single-crystal

monolayer n-type MoS2 on _c_/_a_ sapphire (0001) substrates, with _α_a ranging from 0.2° to 1.0° under 1000 °C annealing for 4 h. To transfer the CVD MoS2 film off the sapphire, PMMA was

spin coated at a speed of 600 r.p.m. for 10 s and 1000 r.p.m. for 45 s and then cured at 100 °C for 2 min, followed by lamination of PDMS. Next, the sample was immersed in deionized water

and the whole stack was spontaneously delaminated from the sapphire and transferred onto a target substrate. Finally, the PDMS/PMMA can be removed by soaking in acetone. DEVICE FABRICATION

On a silicon substrate with 300 nm SiO2, a back-gate was defined by electron-beam lithography (EBL), and 3 nm Ti/60 nm Au was deposited by an electron-beam evaporator. Freestanding PTO film

with 27 nm is then transferred on it. Next, assisted by PDMS/PMMA, the MoS2 film was transferred to the freestanding PTO film. Then, the unnecessary MoS2 is etched by using SF6 and O2 plasma

in a reactive ion etcher. The last step of EBL defined the S/D pattern, and 10 nm Ti/35 nm Pd/10 nm Ti were deposited by the electron-beam evaporator. Finally, an hBN flake with 13 nm

picked up and put down onto the top of the device. ELECTRICAL MEASUREMENTS Electrical characterization of the FETs was performed using a Keithley 4200 semiconductor parameter analyzer and a

Keithley 2450 source meter in a closed-cycle probe station with base pressure ~ 10−6 Torr. DATA AVAILABILITY The data supporting the findings of this study have been included in the main

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212905 (2007). Download references ACKNOWLEDGEMENTS This work is supported by the National Basic Research (Key R&D) Program of China (Nos. 2022YFA1402502 (Y.F.N.), 2022YFB4400100 (X.W.),

 2021YFA1400300 (J.W.H.) and 2021YFA1400400 (Y.F.N.), 2023YFF1500500 (X.W.), 2022YFA1402500 (W.L.) and 2021YFA0715600 (W.L.)), the National Natural Science Foundation of China (Grant No.

12434002 (Y.F.N.), 12172047 (J.W.H.), T2221003 (X.W.), 61927808 (X.W.), 52302181 (L.H.), 12402183 (Y.Z.L.), 62322408 (T.L.), 62204113 (T.L.) and 62304101 (W.L.)), Beijing Natural Science

Foundation (Grant No. 1244057 (Y.Z.L.)), China National Postdoctoral Program for Innovative Talents (Grant No. BX20220147 (L.H.)), China Postdoctoral Science Foundation (Grant No.

2023M731610 (L.H.)), the Xiaomi foundation (L.H.), the Leading-edge Technology Program of Jiangsu Natural Science Foundation (Grant No. BK20232024 (X.W.) and BK20232001 (Y.S.)), the Natural

Science Foundation of Jiangsu Province (Grant No. BK20220773 (T.L.) and BK20230776 (W.L.)) and the Jiangsu Province Key R&D Program (Grant No. BE2023009-3 (W.L.)). The numerical

calculations in this paper have been done on the computing facilities in the High Performance Computing Center (HPCC) of Nanjing University (J.Z.). X.W. acknowledges the support by the New

Cornerstone Science Foundation through the XPLORER PRIZE. The authors would like to express sincere gratitude to the Interdisciplinary Research Center for Future Intelligent Chips (Chip-X)

and Yachen Foundation for their invaluable support. AUTHOR INFORMATION Author notes * These authors contributed equally: Xinrui Yang, Lu Han, Hongkai Ning, Shaoqing Xu, Bo Hao. AUTHORS AND

AFFILIATIONS * National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University,

Nanjing, P. R. China Xinrui Yang, Lu Han, Bo Hao, Yi-Chi Li, Shengjun Yan, Yueying Li, Chenyi Gu, Zhengbin Gu, Jian Zhou, Di Wu & Yuefeng Nie * Collaborative Innovation Center of

Advanced Microstructures, Nanjing University, Nanjing, P. R. China Xinrui Yang, Lu Han, Bo Hao, Shengjun Yan, Yueying Li, Chenyi Gu, Zhengbin Gu, Di Wu & Yuefeng Nie * National

Laboratory of Solid State Microstructures, School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, P. R.

China Hongkai Ning, Yuan Gao, Weisheng Li, Yi Shi & Xinran Wang * School of Aerospace Engineering, Beijing Institute of Technology, Beijing, P. R. China Shaoqing Xu, Yingzhuo Lun & 

Jiawang Hong * School of Integrated Circuits, Nanjing University, Suzhou, P. R. China Taotao Li & Xinran Wang * Interdisciplinary Research Center for Future Intelligent Chips (Chip-X),

Nanjing University, Suzhou, P. R. China Taotao Li & Xinran Wang * Suzhou Laboratory, Suzhou, P. R. China Taotao Li & Xinran Wang Authors * Xinrui Yang View author publications You

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for this author inPubMed Google Scholar CONTRIBUTIONS Y.F.N. conceived the idea and directed the project. X.R.Y. and L.H. synthesized the samples and characterized the crystalline structure

with the help of Y.Y.L. under the supervision of Y.F.N. and Z.B.G.; X.R.Y. and L.H. performed the PFM measurements and data analysis under the supervision of Y.F.N. and D.W.; S.Q.X.

performed finite-element simulation with the help of Y.Z.L. under the supervision of J.W.H.; Y.C.L. performed DFT calculations under the supervision of J.Z.; X.R.Y. and L.H. fabricate

devices with the help of B.H., S.J.Y., H.K.N., Y.G. T.T.L., C.Y.G. and W.S.L. under the supervision of Y.F.N., X.R.W., and Y.S.; H.K.N. and Y.G. performed the electrical measurements of

FeFETs under the supervision of X.R.W. and Y.S.; X.R.Y. and L.H. wrote the manuscript. All authors discussed the data and contributed to the manuscript. CORRESPONDING AUTHORS Correspondence

to Lu Han, Xinran Wang or Yuefeng Nie. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing interests. PEER REVIEW PEER REVIEW INFORMATION _Nature Communications_ thanks

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