Oriented ion migration in dielectric Sb_4O_5Cl_2 single crystals for multifunctional two-dimensional electronics

Domain: physics
Published: 2026-02-20
Editorial outcome: minor_revision

Abstract
Exploring dielectrics with high gate capacitance and artificial tailoring of electronic states is highly desirable for the development of 2D electronics. Here, we report the synthesis of a single-crystalline ionic dielectric Sb4O5Cl2 with aligned ionic channels, achieving a dielectric constant of 23.3 (at a thickness of ~25 nm) and non-volatile programmable regulation of the ionic migration. The fabricated 2D MoS2 transistors display on/off ratios up to 109, leakage currents down to 10−14 A, and mobility of 33.4 cm2 V−1 s−1. Oriented ionic channels facilitate efficient and controllable migration of Cl− ions, thus realizing a non-structural-damage and reconfigurable transition between a quasi-metallic and semiconducting state in MoS2, with a retention time exceeding 3000 s. During 100 cycles of state transitions, the quasi-metallic state exhibits a conductivity of 10−5 S, which is 103 times that of the semiconducting state. Bio-inspired ionic channel further allows neuromorphic devices to integrate image storage, processing, and recognition capabilities, achieving a recognition accuracy improvement from 80.7% to 90.9% within just 5 training epochs through non-volatile preprocessing lasting over 300 s. Our study highlights the significant potential of this single-crystal ionic dielectric as a promising platform for fundamental research on electronic state modulation and advanced electronics.

Introduction
Two-dimensional (2D) electronics have emerged as an ideal platform for studying exotic quantum physics, new functional transistors, and novel computing paradigms, owing to the quantum size effects, the tunable electronic structures, and the strong coupling interactions with external fields of 2D materials1–8. To meet the demands of increasingly complex functionalities, gate dielectrics need not only high dielectric constants to address device-scaling challenges9–12, but also artificial tailoring of electronic states13,14. This dual functionality may allow monolithic integration of multiple operational modes within a single device architecture, such as combining high-performance field-effect transistors (FETs) for digital logic operations15–17, reversible phase transition for analog memory programming18,19, and neuromorphic computing20,21 or other advanced functions. Yet now, conventional metal oxide dielectrics (such as Al2O3, SiO2, and HfO2) still face challenges including low dielectric constants, amorphous structures, and incompatible interfaces induced by dangling bonds, which hinders further miniaturization of devices, limited carrier modulation capabilities and lacking memory characteristics22–26.

In recent years, ionic gate dielectrics have attracted significant attention due to their high-κ dielectric constants from ionic polarization27–29 and the extremely high electric fields enabled by the electric double layer (EDL) of ions30–33, which can significantly enhance the capability of modulating electronic states in 2D materials inducing discrete superconducting phases34, strong Ising-type spin-orbit coupling33, and quenching the bandgap of 2D semiconductors32. However, conventional ionic dielectrics (liquid or solid electrolytes, primarily amorphous or polycrystalline structures) still present formidable challenges including poor compatibility with 2D materials, disordered ion migration pathways leading to random electrical performance and irreversible lattice damage caused by ion-migration resulting in poor stability, thereby severely limiting further research35–38.

In this work, we report a single-crystalline ionic dielectric Sb4O5Cl2, possessing a high κ exceeding 23.3 (~25 nm) and oriented ion-migration paths to address the above mentioned long-term issues. Benefiting from the high κ value and van der Waals structure, 2D transistors exhibit high on/off ratio (109) at a low operation voltage (Vds = 0.5 V), low leakage current (10−14 A), and high room-temperature mobility of 33.4 cm2 V−1 s−1, and realize NOT (inverter), AND, and NAND logic functions. The periodic ionic channels within the single-crystalline structure enhance the efficiency of ionic migration while achieving precise control and non-volatile characteristics. By electrically modulating the ionic states in Sb4O5Cl2, a reversible transition between quasi-metallic and semiconducting states in MoS2 channels has been achieved. This reconfigurability remains stable over 100 cycles and exhibits good retention under both room-temperature and elevated-temperature conditions (over 40 min). The quasi-metallic state shows a conductivity of ~10−5 S, surpassing the semiconducting state by three orders of magnitude, while the ion on/off ratios differ by six orders. Based on this, the device shows good memory properties with good retention (more than 3000 s) and endurance (over 1000 cycles). Furthermore, synapse-like functions integrating image storage, processing, and recognition have been realized. Owing to the non-volatile preprocessing capability lasting over 300 s, the recognition accuracy reaches 90.9% after just 5 training epochs. In summary, our research not only provides a material platform for high-performance 2D electronic devices but also demonstrates its potential in fields such as fundamental studies and multifunctional devices.

Results
Characterization of Sb4O5Cl2 and theory calculations
The Sb4O5Cl2 single crystal, a type of ionic layered material crystallizing in the monoclinic system with space group P2/c (No. 14, a=6.16 Å, b=5.14 Å, c=13.62 Å), features an alternating stack of negatively charged [Cl]2n- anion layers and positively charged [Sb4O5]2n+ layers along the a-axis, exhibiting an interlayer spacing of approximately 6.16 Å (the left part of Fig. 1a). Notably, the Sb and O atoms in the [Sb4O5]2n+ layers are not densely packed. Instead, they form [SbO] eight-membered rings, which align precisely with the interlayer Cl− ions, thereby creating a pathway for Cl− ions migration along the a-axis between layers (the right part of Fig. 1a). Compared with amorphous and polycrystalline ionic materials, the oriented ion-migration within such a single-crystal system under external stimulus facilitates higher ionic concentration accumulation at interfaces, thereby inducing enhanced modulation and coupling effects. The synthesis method of Sb4O5Cl2 single crystals is provided in Methods and Supplementary Fig. 1. The as-synthesized centimeter-scale Sb4O5Cl2 single crystals exhibit three intense and sharp diffraction peaks assigned to the {100} crystallographic planes (Fig. 1b). Although the interlayers in Sb4O5Cl2 are bonded via weak electrostatic interactions-making it more difficult to exfoliate than traditional van der Waals 2D materials-nanosheets were still obtained using a thermally assisted tape exfoliation and transfer method (see Supplementary Fig. 2 and Methods). The obtained Sb4O5Cl2 nanosheets were further confirmed by Raman spectroscopy, and the vibrational modes of their characteristic peaks are assigned via angle-resolved polarized Raman measurements (Supplementary Figs. 3 and 4). These characterizations indicate the highly crystalline layered structure of the as-synthesized Sb4O5Cl2 crystals.

To further elucidate the structure of Sb4O5Cl2, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) characterization was conducted on Sb4O5Cl2 nanosheets. As shown in Fig. 1c, d and Supplementary Fig. 5, we performed HAADF-STEM imaging along different crystallographic orientations of Sb4O5Cl2, namely, [010], [100], and [001], all of which match well with the structure model and lattice spacing of Sb4O5Cl2. Given the contrast dependence of HAADF-STEM on the atomic number (Z) and atomic occupancy39–41, atomic columns containing different quantities of Sb (Z=51) are clearly identified. Notably, the unique interlayer Cl− ions sandwiched between [Sb4O5]2n+ layers can be distinctly observed (Fig. 1c and Supplementary Fig. 6) with an interlayer spacing of 6.16 Å. The measured lattice spacings of 6.81 Å and 5.14 Å correspond to the (002) and (010) lattice planes, respectively. While O atoms remain indiscernible due to their weak contrast arising from a low atomic number, Cl− ions confined within the [SbO] rings are clearly resolved with discernible intensity (Supplementary Fig. 7). Energy-dispersive X-ray spectroscopy (EDS) mapping shows a uniform elemental distribution with an atomic ratio of Sb/O/Cl close to 4:5:2 (Supplementary Fig. 8). Furthermore, high-resolution EDS analysis along the [010] zone axis reveals an alternating stacked distribution of Sb and Cl elements (Fig. 1e), in agreement with the corresponding TEM image. Figure 1f displays the contrast intensity profile extracted along the orange dashed line crossing the [Sb4O5]2n+ layers and the pink dashed line situated within the interlayer regions from Fig. 1c. The profile distinctly reveals the periodic arrangement of Sb and Cl, along with the occupancy of Cl within the interlayer positions. The chemical states of Sb4O5Cl2 were further characterized by X-ray photoelectron spectroscopy (XPS), where the Cl 2p spectral feature centered at a binding energy of 197.7 eV provides conclusive evidence for the existence of interlayer Cl− ions (Supplementary Fig. 9).

We calculated the band structures of Sb4O5Cl2 using density functional theory (Fig. 1g). Sb4O5Cl2 exhibits a large indirect bandgap of ~3.7 eV, whose conduction band minimum (CBM) and valence band maximum (VBM) are located at Z and Γ point of the first Brillouin zone, respectively. Furthermore, the band structure of Sb4O5Cl2 was experimentally determined by ultraviolet-visible absorption spectrum and ultraviolet photoelectron spectrum (UPS) with a bandgap of ~3.9 eV (Fig. 1h and Supplementary Fig. 10), in good agreement with the calculated band structures. Such a wide bandgap renders Sb4O5Cl2 an insulator, as ascertained by the conductive test of a two-terminal device and its resistivity of over 1010 Ω·cm at 300 K can be extracted from the Ids-Vds curve (Supplementary Fig. 11).

Dielectric properties of Sb4O5Cl2
The theoretical dielectric constant of Sb4O5Cl2 was also calculated in Fig. 2a. Sb4O5Cl2 exhibits high dielectric constants across all three crystallographic directions, predominantly originating from ionic polarization (with electronic polarization contributing merely ~5 to the total permittivity). This observation highlights the strong ionic character of Sb4O5Cl2, which arises from its unique crystal structure. Notably, the highest dielectric constant of 32.9 is observed along the a-axis (perpendicular to the [Sb4O5]2n+ layers), which is consistent with the direction of the Sb4O5Cl2 nanosheets obtained by mechanical exfoliation, suggesting a high dielectric controllability of electronic states. The parallel-plate capacitors with vertical metal-insulator-metal (MIM) structure were further fabricated16, as shown in the inset of Fig. 2b. The effective dielectric constant (εeff) of Sb4O5Cl2 nanosheets can be calculated by the equation C = Aε0εeff/t, where C is the measured capacitance, A is the overlapping area of top and bottom electrodes, ε0 is the vacuum dielectric constant and t is the physical thickness of Sb4O5Cl2. The εeff of the 190 nm Sb4O5Cl2 nanosheet, derived from capacitance-frequency (C-f) measurement (Fig. 2b), reaches around 29.5 at 100 kHz and this experimental value aligns remarkably well with theoretical calculations. Thickness-dependent εeff is shown in Fig. 2c. Despite thickness-dependent reduction, Sb4O5Cl2 achieves a dielectric constant of up to 43.2 and maintains a value above 17.5 even at ~15 nm, attributable to its strong ionic polarization mechanism. Additionally, the leakage current and corresponding breakdown field strength of Sb4O5Cl2 were demonstrated in Supplementary Fig. 12, revealing a breakdown field of 3 MV cm−1 while maintaining leakage current below the dynamic random-access memory (DRAM) limit9. The relationship between the bandgap and corresponding dielectric constant of currently reported dielectrics was plotted in Fig. 2d9–11,17,28,29,39,42–47, demonstrating that Sb4O5Cl2 single crystal possesses a relatively higher dielectric constant (as evidenced by εeff = 3.3 for h-BN, εeff = 16.5 for β-Bi2SeO5, εeff = 11.5 for Sb2O3, εeff = 8.4 for CaF2 and εeff = 15.3 for GdOCl).

Single-crystalline ionic dielectric Sb4O5Cl2 for 2D transistors
To examine the potential of Sb4O5Cl2 as a dielectric in devices, MoS2 FETs with Sb4O5Cl2 as the bottom-gate dielectric were fabricated on the SiO2/Si substrate, utilizing exfoliated few-layer graphene (FLG) as gate electrode and In/Au as the source and drain electrodes. Figure 2e shows linear Ids-Vds curves under different gate voltages (Vg), indicating well electrical contacts. The transfer characteristics are presented in Fig. 2f, presenting a high on/off ratio (Ion/Ioff) exceeding 109 at a low operation voltage (Vds = 0.5 V). It is worth noting that even when the operation voltage of Vds is as low as 0.05 V, the transistor still maintains a high Ion/Ioff of 108. Moreover, the device exhibits a low leakage current (~10−14 A) throughout the entire testing process. Furthermore, field-effect mobility of the device reaches 33.4 cm2 V−1 s−1 by linear fitting the transfer curve (Vds = 1 V). The high Ion/Ioff and charge carrier mobility are fundamentally attributed to the superior dielectric constant of Sb4O5Cl2, which originates from robust ionic polarization effects enabled by its ordered ionic migration channels. And the performance of 20 FETs devices was tested and statistically analyzed, as shown in Supplementary Fig. 13. The results demonstrate that the devices exhibit relatively excellent performance in terms of Ion/Ioff, threshold voltage, and mobility, with relatively small variations observed between different devices. Additionally, we fabricated and characterized a top-gated MoS2 device with a Sb4O5Cl2 single-crystal dielectric layer thinner than 100 nm (Supplementary Fig. 14), which also exhibits a high Ion/Ioff exceeding 108. Compared with the 2D transistors with state-of-the-art high-κ dielectrics, our devices exhibit stronger gate controllability (as shown in Fig. 2g), exhibiting higher Ion/Ioff under low operation voltage and much lower leakage current9–11,17,28,29,39,43,44. To evaluate the stability of the Sb4O5Cl2 ionic single-crystal dielectric layer, we conducted positive bias temperature instability (PBTI) and time-dependent dielectric breakdown (TDDB) tests on the MoS2/Sb4O5Cl2/FLG device, and the results are presented in Supplementary Fig. 15.

We also fabricated logic circuits based on MoS2/Sb4O5Cl2 and MoTe2/Sb4O5Cl2 FETs. Supplementary Fig. 16 illustrates the most essential NOT gate (also known as an inverter), which exhibits sharp switching characteristics at different VDD values. More complicated logic units such as the AND gate and the NAND gate were also fabricated (Supplementary Fig. 17). The AND gate and NAND gate operate at VDD of 2.0 V to perform their logical functions. Our results confirm the application potential of the Sb4O5Cl2 ionic single-crystal dielectric layer in logic circuits.

Reconfigurable transition of MoS2
The ion-electron coupling between Sb4O5Cl2 and MoS2 can effectively modulate the carrier concentration in MoS2, thereby further inducing changes in the electrical properties of MoS2. As illustrated in Fig. 3a, the top Sb4O5Cl2 layer functions as a modulation layer, not merely a dielectric. It regulates the direction of Cl− ion migration within itself by adjusting the top ionic gate voltage (Vionic), thus controlling the carrier concentration in MoS2. The SiO2/Si back-gate, in contrast, is used to characterize the modulated electrical behavior of the MoS2 channel.

The Ids-Vds and back-gate transfer characteristics under varying Vionic (+10 V and −10 V for 20 s) are characterized, with the results presented in Fig. 3b, c, respectively. From the Ids-Vds curves, it can be observed that, compared to pristine MoS2, a positive Vionic suppresses Ids while a negative Vionic enhances Ids, which indicates that applying Vionic can effectively modulate the conductivity of MoS2. From the back-gate transfer characteristics, a positive Vionic enhances the n-type semiconductor behavior of MoS2, increasing the Ion/Ioff from 106 to 107. In contrast, after applying a negative Vionic, the device maintains a high conductance state (Ids ~ 10−5 A) throughout the back-gate sweep process, and the Ion/Ioff is less than 10, indicating the transition from semiconducting to quasi-metallic characteristics. Importantly, unlike structure-destructive and irreversible atomic doping48,49, the transition of MoS2 between quasi-metallic and semiconducting state enabled by the modulated Cl− ions of Sb4O5Cl2 exhibits non-destructive nature and high reversibility. By applying gradually increasing negative and positive Vionic to the Sb4O5Cl2 modulation layer, a stepwise transition of MoS2 between semiconducting and quasi-metallic state was achieved, as shown in Fig. 3d, e, respectively. We also tested the retention characteristics of both states at room temperature and elevated temperatures (Supplementary Fig. 18). The state could be maintained for over 40 min even at 100 °C. Furthermore, (Ids-T) curves after different pulsed Vionic demonstrate that the conductance retention can exceed 3000 s (Supplementary Fig. 19). These results indicate that the reconfigurable modulation exhibits a certain degree of non-volatility, and based on this, we successfully fabricated a memory device with good retention (>3000 s) and endurance (>1000 cycles), as shown in Supplementary Fig. 20.

Notably, this reconfigurable transition exhibits good cycling stability. As shown in Fig. 3f, the device underwent 100 cycles of positive-negative Vionic switching while maintaining stable state transfer characteristics. With increasing cycling times, both the quasi-metallic and semiconducting state exhibit minimal fluctuations in Ion/Ioff (Fig. 3g). After 100 cycles, the quasi-metallic state retains an Ion/Ioff below 10, while the semiconducting state maintains a high Ion/Ioff of 105. As demonstrated in Fig. 3h, the quasi-metallic state consistently maintains high conductance (>10−5 S), which is 103 times higher than that of the semiconducting state, while a seven-order-of-magnitude conductance contrast between the two states persists even after 100 cycling tests (Vbg = −10 V). Furthermore, the reconfiguration endurance was extended to 2000 cycles with stable performance. The performance of Sb4O5Cl2-based top-gate FETs was compared before and after cycling, and negligible degradation was observed (Supplementary Fig. 21). These results demonstrate that Sb4O5Cl2 exhibits a remarkably strong non-volatile modulation capability on the electronic states of MoS2, and owing to its unique crystal structure, the physical structural damage caused by this modulation is negligible50.

Mechanism of oriented ion-migration in Sb4O5Cl2
To elucidate the mechanism of tailoring the electronic states, theoretical calculations and systematic experiments were conducted. Piezoresponse force microscopy (PFM) measurements on Sb4O5Cl2 nanosheets ruled out ferroelectric behavior, supported by negligible phase hysteresis and butterfly amplitude loops40, consistent with its centrosymmetric structure (Supplementary Fig. 22). Therefore, we proposed that the migration of Cl− ions at the Sb4O5Cl2/MoS2 interface under the top ionic gate leads to the tailoring of electronic states in MoS2, enabling reconfigurable transitions between quasi-metallic and semiconducting state, as illustrated in Fig. 4a. Under negative Vionic, Cl− ions migrate and accumulate at the Sb4O5Cl2/MoS2 interface, which captures holes in the MoS2 channel, thereby generating more electrons and driving the transition of MoS2 from the initial n-type semiconductor to a quasi-metal. While under positive Vionic, Cl− ions at the interface are depleted, leading to the accumulation of Cl− vacancies (VCl). These VCl capture electrons in the MoS2 channel, reducing the electron concentration and restoring semiconducting behavior. Subsequently, we conducted band structure calculations for MoS2 at two distinct Sb4O5Cl2 interfaces-the Cl− ions interface and the VCl interface-as well as for isolated MoS2, as shown in Fig. 4b, c and Supplementary Fig. 23, respectively. The Fermi level (Ef) of isolated MoS2 is located at the VBM. However, MoS2 shows an upward Ef shift into the conduction band with Cl− ion interface, indicating n-type degenerate doping48. In contrast, the Ef of MoS2 returns to the VBM position with Cl− vacancy interfaces closely matching that of the isolated MoS2, indicating that MoS2 exhibits semiconducting properties at this state. The theoretical calculation results are in excellent agreement with the experimental data and the proposed mechanism.

Furthermore, the ion-migration paths have been calculated, as shown in Fig. 4d. The total energy of the system at each step as the Cl− ions moved through the [Sb4O5]2n+ layer was obtained by relaxing the atomic positions until the maximum force on each atom was less than 10⁻2 eV/Å. To enable efficient Cl− ions migration, the Sb-O bonds surrounding the [SbO] octagonal ring undergo sequential dissociation, driving structural reconfiguration from an octagonal ring through decagonal to dodecagonal configurations, with the entire process exhibiting an energy barrier of 2.10 eV. Compared to ion-migration barriers in other 2D material systems (Fig. 4e)51–53, the Cl− ions migration barrier in Sb4O5Cl2 single crystals is relatively lower (e.g., K+/MoS2: 2.46 eV and Ag+/graphene: 4.27 eV) indicating the inherent migration. Meanwhile, the periodic lattice potential of the single-crystalline Sb4O5Cl2 constrains Cl− migration, imparting a certain degree of non-volatility.

To further confirm this modulation mechanism, we fabricated a MoS2/Sb4O5Cl2/FLG device and employed Kelvin probe force microscopy (KPFM) to characterize the surface potential evolution (Supplementary Fig. 24). As shown in Fig. 4f and Supplementary Fig. 25, the change in the work function is expressed by the contact potential difference (CPD) between the sample surface and the probe tip, as defined by the formula VCPD = (φtip − φsample)/q, where q is the elementary charge, φsample and φtip are the work functions of the sample surface and probe tip54,55. Compared with the pristine KPFM mapping, at Vionic = −20 V, the potential of Sb4O5Cl2 in the edge regions of MoS2 exhibits a significant decrease, which correlates with an increase in the φsample and a downwards shift of the Ef, attributed to the reduction in electron concentration resulting from the accumulation of Cl− ions. Conversely, at Vionic = +20 V, the potential of Sb4O5Cl2 at the MoS2 edges exhibits a significant increase, accompanied by an upward shift of the Ef, as Cl− ions migrate away from the interface, resulting in hole depletion and electron accumulation. Notably, the potential variation in Sb4O5Cl2 was exclusively observed within the overlap regions between the bottom FLG and the top MoS2 layer. This phenomenon is attributed to the migration of Cl− ions occurring only in areas subjected to a vertical electric field, whereas ions migration remains negligible in non-gated regions (as demarcated by the black dashed lines in Fig. 4f). The potential-distance profiles extracted along the yellow and red arrows (Fig. 4f) are shown in Fig. 4g and Supplementary Fig. 26. Initially, the regulated (left part of the black dashed line) and non-regulated (right part of the black dashed line) MoS2 regions exhibited a minor potential difference (−18.2 mV). At Vionic = −20 V, the regulated MoS2 region showed an Ef upshift and potential increase, resulting in a 110.6 mV difference compared to the non-regulated region. Conversely, at Vionic = +20 V, the potential difference reversed to −84.3 mV, indicating an Ef downshift in the regulated MoS2 region that exceeded its initial state (Fig. 4g). The Sb4O5Cl2 at MoS2 edges displayed significant potential inversion (>2 V, Supplementary Fig. 26) under alternating Vionic, driven by Cl− ions depletion and accumulation. KPFM results reveal the band structure evolution of the Sb4O5Cl2/MoS2 heterojunction under varying Vionic (Supplementary Fig. 27), with the Ef shift in MoS2 in excellent agreement with electrical and theoretical data. This highlight that the reconfigurable transition between quasi-metallic and semiconducting state in MoS2 is achieved through efficient Cl− ions migration enabled by the unique crystal structure of Sb4O5Cl2.

Neuromorphic image preprocessing and classification
Leveraging the distinct periodic crystal potential field and the tunable Cl− ions migration behavior of Sb4O5Cl2, we emulate ion-mediated conductance modulation analogous to synaptic plasticity. The detailed biological analogy and transport mechanism are provided in Supplementary Information (Supplementary Fig. 28)56,57. Under positive or negative pulse voltages (Vp), Cl− ions drift directionally within the dielectric, accumulating near or depleting from the MoS2 interface through [SbO] ring channels, as illustrated in Fig. 5a(i), b(i). This dynamic redistribution modulates the local Cl− concentration, thereby tuning the device conductance (Fig. 5a(ii) and Fig. 5b(ii)). The process mimics the depolarization and hyperpolarization behaviors observed in synaptic systems, offering a physically interpretable framework for neuromorphic signal modulation.

Figure 5c presents the conductance retention of the device under single Vp modulation at varying amplitudes. Owing to the migration potential barrier of Cl− ions, the device demonstrates robust retention exceeding 300 s. Nonlinear fitting of the conductance states under different Vp from −5 to −9 V reveals a distinct nonlinear correlation between Vp and conductance states, facilitating linear mapping between image pixels and Vp for effective background noise suppression (Supplementary Figs. 29 and 30). Furthermore, single Vp modulation with a nonlinear conductance response was applied for denoising preprocessing on an image of the word ‘HUST’, embedded with random background noise (σ=0.8). The processed image exhibited significantly enhanced contrast between the letters and background, with the effect sustained for over 300 s (Supplementary Fig. 31). To further explore conductance modulation, a pulse sequence of 100 negative Vp (−7 V) pulses and 100 positive Vp (5.5 V) pulses were applied, each with a duration and interval of 0.2 s (Fig. 5d). This sequence effectively emulated postsynaptic current (PSC) plasticity, exhibiting signal enhancement (depolarization) and suppression (hyperpolarization) characteristics. The observed PSC variations mimic key neurobiological behaviors, specifically pulse-number-dependent long-term potentiation (LTP) and long-term depression (LTD). Figure 5e illustrates the current variation of the device over 45 cycles of 9000-pulse programming, demonstrating excellent robustness at fixed read voltages (−0.5 V, 0 V, and 0.5 V). Moreover, the device performance shows almost no degradation before and after 9000 pulse operations (Supplementary Fig. 32). These results highlight its potential for artificial synapse applications.

By leveraging the nonlinear conductance characteristics of Vp programming control (Supplementary Fig. 29) and the linear LTP/LTD behavior of Vp programming control (Fig. 5d), we developed an integrated preprocessing system coupled with a three-layer artificial neural network (ANN) to recognize the Fashion Modified National Institute of Standard and Technology (Fashion-MNIST) images (Fig. 5f). A detailed description of the system model is presented in Supplementary Fig. 33. To evaluate the device’s potential for background noise suppression, we introduced random background noise (σ=0.8) to the Fashion-MNIST images, with the preprocessed images (Supplementary Fig. 34a and 34b). The results demonstrate that preprocessing significantly facilitated convergence. After just 5 training epochs, the classification accuracy of preprocessed images reached 90.9%, notably surpassing the 80.7% achieved by unprocessed images (Fig. 5g). The corresponding confusion matrix for classification accuracy is depicted in Supplementary Fig. 35. By 20 epochs, the model attained an impressive classification accuracy of approximately 99.1%.

In summary, we present a single-crystalline ionic dielectric, Sb4O5Cl2, featuring oriented ion-migration channels and high ionic polarization, enabling a high dielectric constant of 23.3 (~25 nm) and precise carrier modulation. Through van der Waals integration with MoS2, the fabricated 2D FETs achieve good performance, including a high Ion/Ioff (109), low leakage current (10−14 A), and room-temperature mobility of 33.4 cm2 V−1 s−1 and realize various logic functions. The material further facilitates controllable and non-volatile transition between quasi-metallic and semiconducting state in MoS2, demonstrating 100-cycle reversibility, driven by electric-field-modulated Cl− ions accumulation and depletion at the Sb4O5Cl2/MoS2 interface, which shifts the Ef of MoS2. Based on this mechanism, memory functionality has been achieved with good retention (more than 3000 s), and endurance (over 1000 cycles). Leveraging these properties, we realized neuromorphic devices with synapse-like functions for integrated image storage, processing, and recognition, achieving 90.9% accuracy after 5 training epochs and sustaining non-volatile preprocessing for over 300 s. Our work provides an ionic dielectric material with precise carrier regulation capabilities for developing functional devices and manufacturing advanced electronics.

Methods
Sample synthesis
Single crystals of bulk Sb4O5Cl2 were synthesized by the chemical vapor transport method. The mixture of Sb2O3 powder (Aladdin, 99.9%) and SbCl3 lump (Aladdin, 99.9%) in a molar ratio of 5:2 were placed into a sealed quartz tube under vacuum 10⁻2 Pa. The tube was slowly heated to 823 K on the source zone (T1), while the sink zone (T2) was kept at 723 K. After 7 days, the white plate-like crystals were obtained on the sink zone. For more reaction route details see Supplementary Fig. 1. The nanosheets were isolated from bulk crystals by mechanical exfoliation and transferred to a 300 nm SiO2/Si substrate.

Characterizations
As-grown Sb4O5Cl2 crystals were examined by XRD (D2 phase, Bruker), optical microscope (BX51, Olympus), atomic force microscopy (AFM, Dimension Icon, Bruker), HAADF-STEM and EDS (Tecnai G2 F30, FEI). Raman spectra were performed by a confocal Raman system (Alpha300R, WITec) equipped with a 532 nm laser source. PFM and KPFM measurements were carried out on AFM platform, and different Vionic were applied using a digital source meter (Keithley 2400).

Device fabrication and measurements
To achieve efficient exfoliation and targeted transfer, a two-step method was adopted (as shown in Supplementary Fig. 2). Firstly, scotch tape was used to mechanically exfoliate the Sb4O5Cl2 and transfer them onto the thermally releasable adhesive. Subsequently, the adhesive was heated to release the nanosheets onto a 300 nm SiO2/Si substrate. In this way, more and thinner Sb4O5Cl2 nanosheets could be obtained. Then, to enable targeted transfer, polypropylene carbonate (PPC) solution was first spin-coated and dried at 100 oC for 5 min. After that, polydimethylsiloxane (PDMS) was used to simultaneously transfer the PPC/Sb4O5Cl2 onto the target 2D material (mechanically exfoliated FLG or MoS2).

The metal-insulator-metal capacitors were fabricated as follows: exfoliated FLG was used as bottom electrodes on 300 nm SiO2/Si. The Sb4O5Cl2 nanosheets were transferred onto the bottom electrode using the method described above. The top electrodes were deposited with In/Au (10/40 nm) after electron-beam lithography (EBL). For the back-gate MoS2/Sb4O5Cl2/FLG FETs, MoS2, Sb4O5Cl2, and FLG nanosheets were sequentially transferred and stacked on 300 nm SiO2/Si. Subsequently, after EBL, source-drain electrodes and back-gate electrodes were evaporated onto MoS2 and FLG. For the dual-gate Sb4O5Cl2/MoS2/SiO2 FETs, the fabrication method is the same as back-gate FETs. The electrical measurements were carried out with a semiconductor characterization system (4200SCS, Keithley) and a cryogenic probe station (CRX-6.5, Lake Shore).

Computational methods
We perform the first-principles calculations within the frame of the generalized gradient approximation (GGA) proposed by Perdew, Burke, and Ernzerhof (PBE)58 in the Vienna ab initio simulation package (VASP)59. The 5p, 5s were taken as valence states for Sb, 3s and 3p for Cl, and 2s, 2p for O atoms. The cutoff energy was chosen to 600 eV. The Γ centered k-grids were adopted 6×6×2. The convergence criterion of energy in relaxation was set to be 10⁻5 eV. We fully relaxed the atomic positions until the maximum force on each atom was less than 10⁻2 eV/Å. The Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional60 was employed for the validation of band structures. The Brillouin zone path of the energy band is Γ-X-S-Y-Γ. In order to compute energy barriers, the CINEB method with 8 intermediate images was used to find the transition pathways61. The climbing image method allows for more accurate finding of saddle points with fewer images than the regular NEB method. To simulate the vertical Cl− migration path, a 2×1×1 supercell was constructed along a direction.

Implementation of pattern preprocessing and recognition
To integrate image preprocessing and classification, we employ the Fashion MNIST dataset with σ=0.8 random background noise and preprocess the images using a voltage-dependent nonlinear conductance function (Supplementary Fig. 30). In forward propagation, the preprocessed images are flattened and transformed via a nonlinear transformation using the ReLU activation function: h0 = max (0, x), yielding the hidden layer output h0. The hidden layer output is subsequently processed by a Softmax activation function to obtain the final probability distribution: Softmax(y0i) = Pey0i / Σj ey0j. The classification error is measured using the cross-entropy loss function: L = − Σi=1C yi log(pi), where C=10 denotes the total number of classes, yi is the true label in one-hot encoding, and pi is the predicted probability. In backpropagation, the Adam optimizer updates model parameters, following W = W − η ∂L/∂W, where η = 0.001 is the learning rate, and ∂L/∂W denotes the gradient of the loss function with respect to the weights. Notably, all network weights are mapped to conductance values based on the LTP/LTD characteristics (Supplementary Fig. 33, blue dashed box), ensuring adherence to the physical properties of the device.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this work, Li et al. reports a new single-crystalline ionic dielectric Sb4O5Cl2, with oriented ion-migration channels, designed for high-performance 2D electronics. The material exhibits a high dielectric constant (23.3), ultralow leakage current, and enables reversible metal-semiconductor phase transitions in MoS2 via electric-field-controlled Cl ion migration. The authors demonstrate its application in 2D transistors and neuromorphic devices, where it enhances image recognition accuracy from 80.7% to 90.9% through non-volatile preprocessing. The work combines theoretical calculations, advanced microscopy, and device fabrication to validate its potential for multifunctional electronics. This manuscript is interesting and presents compelling advancements. It provides a brand-new paradigm of dielectric material for 2D semiconductor devices. Therefore, I explicitly recommend the publication of this manuscript in Nature Communications after addressing the following comments:\n1. Sb4O5Cl2 exhibits a distinctive layered structure with intercalated Cl⁻ ions between its anionic [Sb4O5]2+ layers. The interlayer bonding is likely dominated by electrostatic interactions rather than van der Waals forces typical in conventional 2D materials, which would increase the difficulty of mechanical exfoliation. I am curious whether the exfoliation process is the same or different from conventional 2D materials?\n2. The authors have revealed the unique crystal structure of Sb4O5Cl2 through a series of characterization techniques. The STEM images of the (100) plane directly show that Cl⁻ ions are located within asymmetric [SbO] rings, which may lead to significant anisotropy. Thus, have the authors investigated additional anisotropy-related properties, such as anisotropic optical measurements?\n3. The MoS2 FET fabricated with Sb4O5Cl2 as the gate dielectric (Fig. 2f) achieves remarkable electrical characteristics, demonstrating an ultrahigh on/off current ratio exceeding 109 coupled with an exceptionally low leakage current below 10⁻14 A. Could the authors comment on these superior device performances?\n4. The single-crystal ionic dielectric material Sb4O5Cl2 exhibits outstanding dielectric properties. Notably, its unique Cl-ion-controllable migration enables reconfigurable metal-semiconductor phase transitions in MoS2. These remarkable characteristics endow Sb4O5Cl2 with significant potential for applications in 2D semiconductor devices. Could the authors comment on the challenges and opportunities of Sb4O5Cl2 for advanced 2D electronics?", "reviewer_2": "The authors have successfully developed a single-crystalline ionic dielectric material, Sb₄O₅Cl₂, featuring well-oriented ionic channels. Owing to its well-aligned ion-migration pathways and high ionic polarization, this material exhibits a high dielectric constant of up to ~23.3. Through electrical modulation of the accumulation and depletion of Cl⁻ ions at the Sb₄O₅Cl₂/MoS₂ interface, a Fermi-level shift in MoS₂ is induced, thereby enabling reversible phase transitions between the semiconducting and metallic states of MoS₂. Leveraging the biomimetic ion-channel properties of Cl⁻ migration, the device further exhibits neuromorphic functions such as image storage, processing, and recognition. Notably, with non-volatile state retention exceeding 300 s, the recognition accuracy is significantly enhanced after only 5 training epochs. Overall, this study presents comprehensive data and rigorous scientific reasoning. This work is recommended for publication in Nature Communications, but the following issues require clarification prior to formal acceptance:\n1. The manuscript utilizes mechanical exfoliation for device fabrication and characterization. In this regard, it would be valuable to clarify whether chemical vapor deposition (CVD) growth of Sb₄O₅Cl₂ can yield single crystals with the identical stoichiometry (Sb:O:Cl = 4:5:2).\n2. For the dielectric constant measurements of Sb₄O₅Cl₂, parallel-plate capacitance tests employ graphene as contact electrodes. Given that graphene exhibits intrinsic capacitance, it is important to address whether this inherent property compromises the measurement accuracy. Additionally, the rationale for not uniformly adopting metallic electrodes to mitigate such potential interference should be clarified.\n3. In exploring device miniaturization, the thinnest measured sample is ~25 nm. For capacitance-voltage (C-V) characterization, it would be helpful to specify whether thinner samples (e.g., <20 nm) have been attempted. Furthermore, do such ultrathin samples exhibit significant leakage currents or quantum confinement effects that could perturb the measurements?", "reviewer_3": "This manuscript reports on the development of a single-crystalline ionic dielectric, featuring oriented Cl migration channels and a high dielectric constant. The material is integrated with MoS2 to fabricate 2D transistors exhibiting excellent performance metrics, including an on/off ratio exceeding 10**9, low leakage current and high mobility. Furthermore, the authors demonstrate a reversible, non-volatile metal-semiconductor transition in MoS2 through electric-field-controlled Cl⁻ ion migration. The work is technically solid and introduces a compelling dielectric platform for future 2D electronics. However, several critical aspects require clarification and strengthening before publication.\nMajor Points:\n1) Stability and Variability Analysis is Insufficient: The title and claims of the manuscript suggest that Sb₄O₅Cl₂ is a viable dielectric for robust 2D electronics. However, the current work lacks comprehensive assessment of **device variability and long-term operational stability**. There is no data on device-to-device variation, bias stress reliability, or environmental stability, all of which are critical for practical applications. I recommend the authors include:\n* Variability analysis across multiple devices (e.g., threshold voltage, on/off ratio, and mobility distribution).\n* Endurance measurements beyond the reported 100 cycles (e.g., ≥10³ or 10⁴ phase switching cycles).\n* BTI or TDDB data\n* Retention stability under ambient and elevated temperature conditions (preferably >10³ s).\n2) Ionic Migration and Retention Behavior: The authors describe a Cl⁻ ion migration barrier of ~2.1 eV, which is reasonable. However, more detailed quantification of retention behavior under real operating conditions is needed. The reported retention time of >300 s for conductance states and >1200 s for phase configuration is promising but should be extended and compared with standard non-volatile memory benchmarks. Additionally, any signs of ion migration-induced fatigue, spatial drift, or permanent degradation with repeated operation should be discussed.\n3) Neuromorphic Demonstration Lacks Physical Validation: While the authors propose neuromorphic functionality through ion-mediated conductance modulation and simulate its application to image preprocessing and recognition (e.g., Fashion-MNIST dataset), this part remains entirely theoretical. The neuromorphic section relies solely on numerical simulations of an artificial neural network (ANN), with no hardware-level demonstration or integration of actual devices into a functional ANN system. Given the lack of experimental demonstration, this section currently lacks novelty and overstates the practical implications of the work. It is recommended that the neuromorphic content be either significantly condensed or removed unless supported by a physical implementation or hardware prototype. Alternatively, this section could be reframed to clearly emphasize its exploratory nature and potential future directions.\n4) Absence of Circuit-Level Demonstrations: Although the device shows excellent performance metrics, the manuscript would benefit from including simple circuit demonstrations—such as a logic inverter, a memory cell, or an analog computing element—to better support the claim of “multifunctional two-dimensional electronics.” Presenting functional circuits would highlight the integration capability and practical utility of Sb₄O₅Cl₂ beyond the material level.\n5) How stable is Sb₄O₅Cl₂ under prolonged gate bias? Are there any indications of performance drift or hysteresis with repeated cycles?\n6) Have the authors observed any irreversible degradation or shift in threshold voltage across devices after multiple programming cycles?\n7) Can the dielectric be integrated into scalable device platforms with channel lengths below 100 nm?\n8) Can a basic logic or memory function be demonstrated to support claims of multifunctionality?\nMinor Comments and Clarifications:\n1) The term *“biomimetic”* used in the context of neuromorphic image processing is overstated. Since there is no biological interfacing or experimentally validated mimicry of neural functions, the term should be replaced with *“bio-inspired”* or qualified appropriately.\n2) Please clarify whether the reported ultralow leakage current remains stable after repeated modulation cycles or environmental exposure.\n3) The device architecture includes both top and bottom gates. A clearer explanation of their respective roles and independent control during modulation experiments would be helpful.\n4) Can the dielectric thickness be scaled below 100 nm while maintaining the dielectric strength and performance?"}, "author_response": "Reviewer #1:\nIn this work, Li et al. reports a new single-crystalline ionic dielectric Sb O Cl , with\n4 5 2\noriented ion-migration channels, designed for high-performance 2D electronics. The\nmaterial exhibits a high dielectric constant (23.3), ultralow leakage current, and enables\nreversible metal-semiconductor phase transitions in MoS via electric-field-controlled\nneuromorphic devices, where it enhances image recognition accuracy from 80.7% to\n90.9% through non-volatile preprocessing. The work combines theoretical calculations,\nadvanced microscopy, and device fabrication to validate its potential for multifunctional\nelectronics. This manuscript is interesting and presents compelling advancements. It\nprovides a brand-new paradigm of dielectric material for 2D semiconductor devices.\nTherefore, I explicitly recommend the publication of this manuscript in Nature\nCommunications after addressing the following comments:\nQ1. Sb O Cl exhibits a distinctive layered structure with intercalated Cl⁻ ions between\n4 5 2\nits anionic [Sb O ]2+ layers. The interlayer bonding is likely dominated by electrostatic\n4 5\ninteractions rather than van der Waals forces typical in conventional 2D materials,\nwhich would increase the difficulty of mechanical exfoliation. I am curious whether the\nexfoliation process is the same or different from conventional 2D materials?\nResponse: Thanks for your comments and suggestions. Unlike traditional van der\nWaals two-dimensional materials, the interlayer forces in Sb O Cl are weak\n4 5 2\nelectrostatic interactions. Consequently, the conventional exfoliation method yields\nrelatively thicker Sb O Cl nanosheets with low production efficiency. In this work, to\n4 5 2\nacquire more and thinner Sb O Cl nanosheets, we adopted thermally assisted tape\n4 5 2\nexfoliation and transfer method illustrated in Figure R1-1. Specifically, Sb O Cl single\n4 5 2\ncrystal bulk was exfoliated using thermal release tape to obtain nanosheets, which were\nthen released onto a SiO /Si substrate. Subsequently, polypropylene carbonate (PPC)\n2\nwas spin-coated, and a polymethyl methacrylate (PMMA) layer was used to transfer\nthe PPC/Sb O Cl nanosheets onto MoS . After removing excess PPC, devices were\n4 5 2 2\nfabricated via electron beam lithography (EBL) and thermal evaporation. To reflect the\nreviewer’s concerns, we have added the schematic diagram in Supplementary Fig. 2\nand the related description in lines 3-6, page 5 of the revised main text. Detailed\nprocedures are provided in the Methods section.\nFigure R1-1. Schematic diagram of mechanical exfoliation and transfer of Sb₄O₅Cl₂.\nQ2. The authors have revealed the unique crystal structure of Sb O Cl through a series\n4 5 2\nof characterization techniques. The STEM images of the (100) plane directly show that\nCl⁻ ions are located within asymmetric [SbO] rings, which may lead to significant\nanisotropy. Thus, have the authors investigated additional anisotropy-related properties,\nsuch as anisotropic optical measurements?\nResponse: Thanks for your kind suggestions. We investigated polarized Raman\nspectroscopy of Sb O Cl nanosheets, as shown in Figure R1-2. The intensity of the\n4 5 2\nRaman modes can be expressed as: 𝐼 ∝ |𝒆 ∙𝑹∙𝒆 |2, where ei and es represent the\n𝑖 𝑠\npolarization vectors of incident laser and Raman signal, R is the Raman tensor. For\nSb O Cl , e, 𝑒∥ and 𝑒⊥ are described as ei = (0, cosθ, sinθ), 𝑒∥ = (0, cosθ, sinθ)\n4 5 2 i 𝑠 𝑠 𝑠\nand 𝑒⊥ = (0, -sinθ, cosθ). Since Sb O Cl belongs to P21/c space group, the Raman\ns 4 5 2\ntensor can be described:\n𝑎 𝑑 0 0 0 𝑒\n𝑹(𝐴 ) = (𝑑 𝑏 0) 𝑹(𝐵 ) = (0 0 𝑓)\ng 𝑔\n0 0 𝑐 𝑒 𝑓 0\nWhere 𝑎, 𝑏, 𝑐, 𝑑, 𝑒 and 𝑓 are matrix element of the Raman tensor.\n𝐼(𝐴 ,∥) ∝ (𝑏+𝑐+𝑏𝑐𝑜𝑠2𝜃 −𝑐𝑐𝑜𝑠2𝜃)2\ng\n𝐼(𝐴 ,⊥) ∝ (𝑐𝑠𝑖𝑛2𝜃 −𝑏𝑐𝑜𝑠2𝜃)2\ng\n𝐼(𝐵 ,∥) ∝ |𝑓|2𝑠𝑖𝑛22𝜃\ng\n𝐼(𝐵 ,⊥) ∝ |𝑓|2𝑐𝑜𝑠22𝜃\ng\nAfter fitting, the peaks 77, 138, and 272 cm−1 are assigned to A mode, the peak 170\ng\nand 203 cm−1 are B mode. To reflect the reviewer’s concerns, we have added the new\ng\nexperimental result in Supplementary Fig. 4, and the related description in lines 6-9,\npage 5 of the revised main text.\nFigure R1-2. The angle-dependent Raman intensities of the five Raman main peaks\nplotted in polar coordinates.\nQ3. The MoS FETs fabricated with Sb O Cl as the gate dielectric (Fig. 2f) achieves\n2 4 5 2\nremarkable electrical characteristics, demonstrating an ultrahigh on/off current ratio\nexceeding 109 coupled with an exceptionally low leakage current below 10⁻14 A. Could\nthe authors comment on these superior device performances?\nResponse: Thanks for your kind suggestions. Sb O Cl is a novel ionic dielectric\n4 5 2\nmaterial. Its unique ionic relaxation polarization mechanism endows it with a high\ndielectric constant (Nat Mater 2025, 24, 197.). Additionally, under an external electric\nfield, it can generate a strong internal screening field through ion displacement (electric\ndouble-layer, EDL), which almost completely cancels out the net electric field within\nthe dielectric (Nat. Nanotechnol. 2024, 19, 932). This extremely low net electric field\neffectively suppresses most leakage mechanisms dependent on electric field strength\n(such as tunneling, emission, and ohmic conduction), resulting in an ultralow leakage\ncurrent level.\nQ4. The single-crystal ionic dielectric material Sb O Cl exhibits outstanding dielectric\n4 5 2\nproperties. Notably, its unique Cl-ion-controllable migration enables reconfigurable\nmetal-semiconductor phase transitions in MoS . These remarkable characteristics\n2\nendow Sb O Cl with significant potential for applications in 2D semiconductor\n4 5 2\ndevices. Could the authors comment on the challenges and opportunities of Sb O Cl\n4 5 2\nfor advanced 2D electronics?\nResponse: Thanks for your kind suggestions. Sb O Cl single-crystal ionic dielectric\n4 5 2\nlayers, with their high dielectric constant and atomically clean interfaces, serve as an\nideal dielectric material for two-dimensional semiconductors. Additionally, the unique\nion migration channels in Sb O Cl provide efficient ion transport pathways and enable\n4 5 2\nion-electron coupling effects at the interface, achieving precise modulation of MoS₂\nelectrical conductivity, which gives it potential for application in the field of 2D\nmultifunctional electronic devices. However, the current reliance on non-scalable\nmechanical exfoliation methods for obtaining nanosheets hinders further research and\ndevelopment. Therefore, achieving the preparation of wafer-scale two-dimensional\nSb O Cl single-crystal films is crucial. Currently, substrate engineering in chemical\n4 5 2\nvapor deposition (CVD)—such as using vicinal substrate steps to guide epitaxial\ngrowth—has enabled wafer-scale single-crystal synthesis of various 2D materials like\nMoS , WS and so on, offering a feasible pathway (Nat. Nanotechnol. 2021, 16, 1201;\n2 2\nNat. Nanotechnol. 2021, 17, 33). However, given the low-symmetry crystal structure of\nSb O Cl , it is necessary to identify suitable substrates and corresponding step\n4 5 2\norientations. Furthermore, due to the potential diversity of synthesis products, strict\ncontrol over the stoichiometric ratio of reactants is essential, as it directly determines\nthe final phase and quality of the product. By addressing these challenges and\ncapitalizing on the opportunities, we can pave the way for the widespread adoption of\nSb O Cl in various technological domains.\n4 5 2\nReviewer #2:\nThe authors have successfully developed a single-crystalline ionic dielectric material,\nSb₄O₅Cl₂, featuring well-oriented ionic channels. Owing to its well-aligned ion-\nmigration pathways and high ionic polarization, this material exhibits a high dielectric\nconstant of up to ~23.3. Through electrical modulation of the accumulation and\ndepletion of Cl⁻ ions at the Sb₄O₅Cl₂/MoS₂ interface, a Fermi-level shift in MoS₂ is\ninduced, thereby enabling reversible phase transitions between the semiconducting and\nmetallic states of MoS₂. Leveraging the biomimetic ion-channel properties of Cl⁻\nmigration, the device further exhibits neuromorphic functions such as image storage,\nprocessing, and recognition. Notably, with non-volatile state retention exceeding 300 s,\nthe recognition accuracy is significantly enhanced after only 5 training epochs. Overall,\nthis study presents comprehensive data and rigorous scientific reasoning. This work is\nrecommended for publication in Nature Communications, but the following issues\nrequire clarification prior to formal acceptance:\nQ1. The manuscript utilizes mechanical exfoliation for device fabrication and\ncharacterization. In this regard, it would be valuable to clarify whether chemical vapor\ndeposition (CVD) growth of Sb₄O₅Cl₂ can yield single crystals with the identical\nstoichiometry (Sb:O:Cl = 4:5:2).\nResponse: Thanks for your suggestions. We’ve successfully synthesized Sb O Cl\n4 5 2\nnanosheets via CVD, as shown in Figure 2R-1. Using a specific ratio of Sb O and\n2 3\nSbCl as reaction sources, single-crystal nanosheets were preliminarily obtained on a\n3\ndownstream sapphire substrate at a reaction temperature of 500 °C and the size of the\nnanosheets is around 10 μm. These nanosheets exhibited Raman characteristic peaks\n(77, 137, 170, 205 and 272 cm-1 ) consistent with Sb O Cl , and Raman mapping\n4 5 2\nconfirmed their well-defined crystalline quality. These results demonstrate the\nfeasibility of precisely synthesizing single-crystal Sb O Cl nanosheets via the CVD\n4 5 2\nmethod.\nFigure R2-1. Chemical vapor deposition of Sb O Cl nanosheets. a, Schematic\n4 5 2\nillustration of a CVD setup to synthesize Sb O Cl nanosheets on mica. b, and c, Optical\n4 5 2\nmicrographs of synthesize Sb O Cl nanosheets. d, Raman spectra and intensity map of\n4 5 2\nSb O Cl nanosheets.\n4 5 2\n2. For the dielectric constant measurements of Sb₄O₅Cl₂, parallel-plate capacitance tests\nemploy graphene as contact electrodes. Given that graphene exhibits intrinsic\ncapacitance, it is important to address whether this inherent property compromises the\nmeasurement accuracy. Additionally, the rationale for not uniformly adopting metallic\nelectrodes to mitigate such potential interference should be clarified.\nResponse: Thanks for your kind suggestions. Graphene was selected as the electrode\nprimarily due to its excellent electrical conductivity, atomically flat surface, and\npotential compatibility with future flexible electronic devices, all of which contribute to\na more accurate characterization of the intrinsic properties of Sb O Cl . Theoretically,\n4 5 2\ngraphene does possess quantum capacitance, but its magnitude is significantly smaller\nthan the capacitance of the Sb O Cl dielectric layer. Thus, its impact on the measured\n4 5 2\ndielectric constant is negligible. Moreover, the use of graphene as contact electrodes\nfor capacitance testing is also commonly adopted in other two-dimensional dielectric\nmaterial systems (e.g., Bi SiO , Nat. Commun.2023, 14, 4406; MoO , Nat.\n2 5 3\nCommun.2025, 16, 6758). To further verify this, we compared devices fabricated with\nmetal electrodes under identical conditions, as shown in Figure R2-2. The dielectric\nconstants measured using metal electrodes were in good agreement with those obtained\nusing graphene electrodes, which further demonstrates that the intrinsic capacitance\nof graphene did not introduce significant deviation in the evaluation of the dielectric\nproperties.\nFigure R2-2. Dielectric constant of Sb O Cl nanosheets. a, Optical micrograph image\n4 5 2\nof metal-insulator-metal device. b, Typical frequency-dependent capacitance (C-f)\ncharacteristics of parallel-plate capacitor device.\nQ3. In exploring device miniaturization, the thinnest measured sample is ~25 nm. For\ncapacitance-voltage (C-V) characterization, it would be helpful to specify whether\nthinner samples (e.g., <20 nm) have been attempted. Furthermore, do such ultrathin\nsamples exhibit significant leakage currents or quantum confinement effects that could\nperturb the measurements?\nResponse: Thanks for your kind suggestions. We have successfully fabricated parallel-\nplate capacitor device using Sb O Cl with thicknesses down to approximately 15 nm\n4 5 2\nand measured its capacitance. The calculated dielectric constant remains notably high\nat 17.5 (Figure R2-3 a-c). Despite a slight decrease in dielectric constant with further\nthickness reduction, the material retains competitively robust dielectric performance.\nFurthermore, we constructed field-effect transistors (FETs) based on thin Sb O Cl\n4 5 2\ndielectric layers, which demonstrated a switching ratio of 108 and a leakage current as\nlow as 10-12 A. No significant leakage current or quantum confinement effects were\nobserved in these ultrathin samples (Figure R2-3 d-f). To reflect the reviewer’s\nconcerns, we have added the new experimental result in Fig. 2c and the related\ndescription in lines 3-5, page 7 of the revised main text.\nFigure R2-3. The metal-insulator-metal and FETs devices based on thin Sb O Cl\n4 5 2\nnanosheets. a, Optical micrograph image of metal-insulator-metal device. b, AFM\nimage and the corresponding height profile of Sb O Cl nanosheet in a. c, Typical\n4 5 2\ncapacitance-voltage (C-V) characterization of parallel-plate capacitor device. d,\nOptical micrograph image of top-gated Sb O Cl /MoS FETs. e, AFM image and the\n4 5 2 2\ncorresponding height profile of Sb O Cl nanosheet in d. f, Transfer characteristics of\n4 5 2\nthe back-gated MoS /Sb O Cl FETs.\n2 4 5 2\nReviewer #3:\nThis manuscript reports on the development of a single-crystalline ionic dielectric,\nfeaturing oriented Cl migration channels and a high dielectric constant. The material is\nintegrated with MoS to fabricate 2D transistors exhibiting excellent performance\n2\nmetrics, including an on/off ratio exceeding 109, low leakage current and high mobility.\nFurthermore, the authors demonstrate a reversible, non-volatile metal-semiconductor\ntransition in MoS through electric-field-controlled Cl⁻ ion migration. The work is\n2\ntechnically solid and introduces a compelling dielectric platform for future 2D\nelectronics. However, several critical aspects require clarification and strengthening\nbefore publication.\nMajor Points:\nQ1. Stability and Variability Analysis is Insufficient: The title and claims of the\nmanuscript suggest that Sb₄O₅Cl₂ is a viable dielectric for robust 2D electronics.\nHowever, the current work lacks comprehensive assessment of **device variability and\nlong-term operational stability**. There is no data on device-to-device variation, bias\nstress reliability, or environmental stability, all of which are critical for practical\napplications. I recommend the authors include:\n* Variability analysis across multiple devices (e.g., threshold voltage, on/off ratio, and\nmobility distribution).\n* Endurance measurements beyond the reported 100 cycles (e.g., ≥10³ or 10⁴ phase\nswitching cycles).\n* BTI or TDDB data\n* Retention stability under ambient and elevated temperature conditions\n(preferably >10³ s).\nResponse: Thanks for your comments and suggestions. We fully agree that a\ncomprehensive evaluation of device variability and long-term operational stability is\ncrucial to substantiate our claim regarding the viability of Sb₄O₅Cl₂ as a robust\ndielectric for practical 2D electronics. The reviewer's suggestions are highly valuable,\nand we have conducted additional experiments as recommended to address these points.\nAs suggested, we have performed statistical analysis on 20 MoS /Sb O Cl /FLG FETs,\n2 4 5 2\nwith the results presented in the new Figure R3-1. The key parameters show excellent\nconsistency with variations within ±15%, specifically an average on/off ratio of 9×10⁹,\nthreshold voltage of -13.5 V, and mobility of 40 cm2/V·s. These statistical results\ndemonstrate that the MoS /Sb O Cl FETs achieve competitive performance while\n2 4 5 2\nmaintaining low device-to-device variability. To reflect the reviewer’s concerns, we\nhave added the new experimental results in Supplementary Fig. 13 and the related\ndescription in lines 28-30, page 7 of the revised main text.\nFigure R3-1. Statistical histogram from 20 devices. a, Current on/off ratio (I /I ). b,\non off\nThreshold voltage (V ). c, Mobility.\nth\nFigure R3-2. Metal-semiconductor transition of MoS . a, 2000 phase transition cycles.\n2\nb, I /I of two phases during 2000 cycles extracted from a.\non off\nAs for the phase switching endurance, we have conducted further tests extending\nthe number of cycles to 2,000 and the on/off ratios for both the metallic and\nsemiconducting phases during these 2,000 cycles were extracted separately, as shown\nin Figure R3-2. It can be observed that the device still achieves clear metal-\nsemiconductor phase transition after 2,000 cycling operations. In the metallic phase,\nthe device exhibits high conductivity characteristics with an on/off ratio of less than 10\nunder back-gate sweeping. Although the on/off ratio in the semiconducting phase\ndecreases with increasing cycle number, it remains greater than 10⁵, demonstrating\ngood cycling stability. We have added the new experimental results in Supplementary\nFig. 21, and the related description in lines 28-29, page 9 of the revised main text.\nFigure R3-3. BTI and TDDB tests results. a, PBTI result of two MoS /Sb O Cl /FLG\n2 4 5 2\nFETs. b, TDDB result.\nIn response to the reviewer's suggestion, we also have supplemented the PBTI and\nTDDB tests, as shown in Figure R3-3. Under PBTI testing conditions at 125°C and 10V\nstress bias, we measured two MoS / Sb O Cl FETs and extracted power-law exponents\n2 4 5 2\nof 0.25 and 0.33, respectively (Figure R3-3a). These values are comparable to those\nobserved in HfO₂-based systems, indicating that the primary degradation mechanism\nis the reaction-diffusion (R-D) process (Jpn J Appl Phys 2004, 43, 7807.; IEEE Trans.\nElectron Devices 2003, 50, 1517.). Under combined electrical and thermal stress,\nelectrochemical degradation occurs at the gate dielectric/channel interface, leading to\nthe generation of new interface states. Additionally, the presence of trap-assisted\ntunneling suggests the existence of bulk traps or defect states at the Sb O Cl dielectric\n4 5 2\ninterface, which may be attributed to chlorine ion vacancies generated at the interface\nafter exfoliation. The TDDB results are shown in Figure R3-3b. Under the high-voltage\nstress of 40 V, the device breakdown exhibits three distinct stages. Initially (0-1000 s),\nthe leakage current remains stable at a low level of approximately 10⁻12 to 10⁻11 A,\nindicating excellent insulating properties of the Sb O Cl dielectric layer in its pristine\n4 5 2\nstate. Subsequently, the leakage current shows \"fluctuations\" and gradually increases\nto 10⁻9 A, at which point defects within the Sb O Cl dielectric layer accumulate,\n4 5 2\nforming unstable conductive paths and leading to a soft breakdown. Finally, at around\n7000 s, the leakage current abruptly surges to 10⁻5 A, indicating a complete hard\nbreakdown of the Sb O Cl dielectric layer. We attribute the primary failure mechanism\n4 5 2\nto the susceptibility of its intrinsic defects (such as Cl vacancies) to the electric field\nand the positive feedback degradation induced by ion migration. To reflect the\nreviewer’s concerns, we have added the new experimental results in Supplementary Fig.\n15 and the related description in lines 7-10, page 8 of the revised main text.\nFigure R3-4 Metal and semiconductor phases retention stability at room temperature\n(a) and elevated temperature (b).\nFurthermore, the retention characteristics of the metal-semiconductor phase\ntransition were evaluated at both room temperature and 100°C. As illustrated in Figure\nR3-4, both phases exhibited excellent stability at room temperature, retaining their\nstates for over 120 minutes. The metallic phase showed negligible degradation, while\nthe semiconducting phase experienced a modest increase (by two orders of magnitude)\nin the off-state current. At an elevated temperature of 100°C, the retention times for\nboth phases decreased but remained above 40 minutes. This thermally accelerated\ndecay is attributed to an increase in the system's free energy, which enhances the\nmobility of Cl⁻ ions and facilitates their transition back to the initial state. We have\nadded the new experimental results in Supplementary Fig. 18 and the related\ndescription in lines 11-13, page 9 of the revised main text.\nQ2. Ionic Migration and Retention Behavior: The authors describe a Cl⁻ ion migration\nbarrier of ~2.1 eV, which is reasonable. However, more detailed quantification of\nretention behavior under real operating conditions is needed. The reported retention\ntime of >300 s for conductance states and >1200 s for phase configuration is promising\nbut should be extended and compared with standard non-volatile memory benchmarks.\nAdditionally, any signs of ion migration-induced fatigue, spatial drift, or permanent\ndegradation with repeated operation should be discussed.\nResponse: Thanks for your kind suggestions. Additional retention tests further\nsubstantiate the stability of the ion-migration mechanism. At room temperature, both\nphases were stable for >120 minutes, a property maintained for >40 minutes even at\n100°C (Figure R3-5). Moreover, distinct conductance states programmed by the ion-\ngate were retained for over 3000 seconds (Figure R3-6). It offers comparable retention\nand endurance to current 2D material-based memories, and exhibits better\nperformance compared to currently reported ion-based devices. (as shown in Table R3-\n1). These results collectively demonstrate the robust retention characteristics of\nSb O Cl under electric-field-driven ion migration. Furthermore, we investigated the\n4 5 2\nfatigue damage induced by repeated ion migration operations. The surface topography\nof the device was characterized before and after extensive 100 cycles, as shown in\nFigure R3-7. Compared to the pristine state, distinct protrusions emerged on the\nSb O Cl surface surrounding the MoS flake after cycling. Compared to the initial state,\n4 5 2 2\nafter 100 cycles, slight morphological undulations appeared on the Sb O Cl surface.\n4 5 2\nThis observation suggests that the repeated cross-layer migration of Cl⁻ ions has led to\na certain degree of morphological distortion in the Sb O Cl lattice, which may be the\n4 5 2\nreason for the slight performance degradation observed after multiple cycles. To reflect\nthe reviewer’s concerns, we have added the new experimental results in Supplementary\nFig. 18, 19 and the related description in lines 11-15, page 9 of the revised main text.\nFigure R3-5 Metal and semiconductor phases retention stability at room temperature\n(a) and elevated temperature (b).\nFigure R3-6 Retention of different conductance states after different V .\nionic\nDevice Device\nRetention Endurance Reference\nstructure type\nNat.\nMoS /hBN/MLG/SiO Floating- >2000\n2 2 >5400 s Nanotechnol.\ngate cycles\n/Si 2021, 16, 882.\nMoS /HfO /Pt/\n2 2 Floating- Not Nature 2020,\n>3600 s\ngate mentioned 587, 72.\nHfO /Au\nMoS /h-BN/Gr >1000 s\n2 gate mentioned 2023, 14, 3070\nMoS /hBN/ Adv. Mater.\n>1000 s 2022, 34,\ngate cycles\n2D-RPP/SiO /Si 2110278.\n>4000 s 2024, 36,\ngate cycles\nSiO /Si 2308502.\n2 4 9 Floating- >2000\n>1000 s 2022, 34,\ngate cycles\nSiO /Si 2204982\n2\n3R-MoS / >10000 Nat. Electron.\ncycles 2024, 7, 29.\nh-BN/Si\nNat. Mater.\nNot\n3R-MoS /Al O /Si Ferroelectric >100 s 2025, 24,\n2 2 3 mentioned\n1195.\nNat. Commun.\n>250\nCuInP S Ferroionic >1000 s 2025, 16,\n2 6 cycles\n4462.\nAdv. Mater.\n>1000\nCdSb Se Br Ionic >1000 s 2024, 36,\n2 3 2 cycles\n2406984.\nAdv. Mater.\n>50\nH Na In As Ionic >300 s 2025, 37,\nx 2-x 2 3 cycles\n2500056.\n>1000\nMoS /Sb O Cl /FLG Ionic >3000 s This work\n2 4 5 2 cycles\nTable R3-1. Comparison of the performance of MoS /Sb O Cl /FLG memory device\n2 4 5 2\nwith other memory devices based on 2D materials.\nFigure R3-7 AFM images of the MoS /Sb O Cl /FLG device in its pristine state and\n2 4 5 2\nafter cycling\nQ3. Neuromorphic Demonstration Lacks Physical Validation: While the authors\npropose neuromorphic functionality through ion-mediated conductance modulation and\nsimulate its application to image preprocessing and recognition (e.g., Fashion-MNIST\ndataset), this part remains entirely theoretical. The neuromorphic section relies solely\non numerical simulations of an artificial neural network (ANN), with no hardware-level\ndemonstration or integration of actual devices into a functional ANN system. Given the\nlack of experimental demonstration, this section currently lacks novelty and overstates\nthe practical implications of the work. It is recommended that the neuromorphic content\nbe either significantly condensed or removed unless supported by a physical\nimplementation or hardware prototype. Alternatively, this section could be reframed to\nclearly emphasize its exploratory nature and potential future directions.\nResponse: Thanks for your kind suggestions. To reflect the reviewer’s suggestion, we\nhave reframed the narrative in the text to explicitly position this part of the work as\nexploratory research highlighting potential future directions. We have also revised and\nstreamlined the section on neuromorphic functionality in lines 15-25, page 12 of the\nrevised main text. Figure 5 and Supplementary Fig. 28 have been further modified\naccordingly\nQ4. Absence of Circuit-Level Demonstrations: Although the device shows excellent\nperformance metrics, the manuscript would benefit from including simple circuit\ndemonstrations—such as a logic inverter, a memory cell, or an analog computing\nelement—to better support the claim of “multifunctional two-dimensional electronics.”\nPresenting functional circuits would highlight the integration capability and practical\nutility of Sb₄O₅Cl₂ beyond the material level.\nResponse: Thanks for your kind suggestions. To better support the claim of\n\"multifunctional two-dimensional electronics,\" we have conducted additional research\non the application of the Sb O Cl ionic single-crystal dielectric layer in logic inverters\n4 5 2\nand memory devices, as suggested by the reviewers, and constructed corresponding\ndevices for testing. First, Figure R3-8 demonstrates a logic inverter based on Sb O Cl ,\n4 5 2\nwhere MoS and MoTe are used as channel materials for the NMOS and PMOS,\n2 2\nrespectively. The device circuit and optical micrograph are shown in Figure R3-8a. The\ninverter exhibits sharp switching characteristics at different V values, and the\ndd\ncorresponding gain has been extracted. Additionally, the implementation of AND and\nNAND logic gates using Sb O Cl (Figure R3-9) further demonstrates its application\n4 5 2\npotential in the field of logic devices.\nThe memory function of the MoS /Sb O Cl /FLG device is illustrated in Figure R3-\n2 4 5 2\n10. The device structure and corresponding optical micrograph are shown in Figure\nR3-10a. Owing to the accumulation and depletion of interfacial Cl⁻ ions under\nsweeping gate voltage, the transfer characteristics exhibit a significant memory\nwindow across different gate voltage scan ranges (Figure R3-10b). The size of this\nmemory window shows a proportional relationship with the gate voltage scan range\n(Figure R3-10c). Furthermore, the device demonstrates notable non-volatile\ncharacteristics: the current levels in the programmed state (+15 V) and erased state (-\ndifference between the two states. Additionally, under identical pulse duration and\nsource/drain bias conditions, the current levels of both states remain unchanged after\nmore than 1000 cycles, indicating robust endurance. The successful implementation of\nthese logic and memory applications further validates the potential of Sb O Cl ionic\n4 5 2\nsingle-crystal dielectric for use in multifunctional 2D electronic devices. To reflect the\nreviewer’s concerns, we have added the new experimental results in Supplementary Fig.\n16, 17, and 20, and included relevant descriptions in lines 11-17 on page 8 and lines\n15-18 on page 9 of the main text.\nFigure R3-8. Logic inverter based on Sb O Cl . a, Circuit diagram (upper) and optical\n4 5 2\nimage of a typical complementary inverter composed of MoS and MoTe FETs based\n2 2\non Sb O Cl crystal dielectric. Scale bars, 10 μm. b, The voltage transfer\n4 5 2\ncharacteristics of the inverter as a function of the input voltage with different V from\nDD\n0.5 to 3V. c, The corresponding voltage gains of the resulting inverter.\nFigure R3-9. Logic functions based on Sb O Cl . a, Optical image of logic device\n4 5 2\ncomposed of MoS and MoTe FETs based on Sb O Cl crystal dielectric. Scale bars,\n2 2 4 5 2\n10 μm. b, Circuit diagram of AND and NAND gates. c, Input–output logic functions of\nthe AND gate with an V of 2 V. d, Input–output logic functions of the NAND gate with\nDD\nan V of 2 V.\nDD\nFigure R3-10. Memory function based on MoS /Sb O Cl /FLG back-gated FETs. a,\n2 4 5 2\nSchematic diagram of the device structure and optical microscope image. Scale bars,\n10 μm. b, Transfer curves under different control gate voltages. c, Memory window\nwidth as a function of maximum control gate voltage, V . d, Retention of device. The\ng, max\nretention is measured by applying a V pulse of −15 V (red) or +15 V (blue). Pulse\nionic\nwidth is 400ms. e, Endurance characteristics of device. Switching between the erase\nstate (red) and the program state (blue) is realized by changing the sign of the V\nionic\npulse. Pulse amplitude is 15 V, and pulse width is 400 ms.\nQ5. How stable is Sb₄O₅Cl₂ under prolonged gate bias? Are there any indications of\nperformance drift or hysteresis with repeated cycles?\nResponse: Thanks for your kind suggestions. We performed PBTI testing on the\nSb O Cl -based MoS₂ FETs, as shown in Figure R3-11a, the threshold voltage of the\n4 5 2\nFETs shifted only minimally, indicating good stability under prolonged gate bias.\nFurthermore, we compared the transfer characteristic curves of the MoS / Sb O Cl\n2 4 5 2\ndevice before and after 2000 phase-change cycles, as presented in Figure R3-11b. After\nmultiple cycles, the FETs exhibited a noticeable threshold voltage shift and a reduction\nin the on-state current. However, the I /I ratio remained largely unchanged,\non off\nconsistently exceeding 108. We attribute the observed degradation after 2000 cycles to\nthe accumulation of irreversible structural damage in the material caused by ion\nhopping during the cycling process. To reflect the reviewer’s concerns, we have added\nthe new experimental results in Supplementary Fig. 15a and 21c, and the related\ndescription in lines 7-10, page 8 and lines 28-29, page 9 of the revised main text.\nFigure R3-11. a, PBTI result of two MoS /Sb O Cl /FLG FETs. b, Transfer\n2 4 5 2\ncharacteristics of device before and after 2000 phase transition cycles.\nQ6. Have the authors observed any irreversible degradation or shift in threshold voltage\nacross devices after multiple programming cycles?\nResponse: Thanks for your kind suggestions. We compared the transfer characteristic\ncurves of the FETs before and after 9,000 pulse operations (equivalent to 45\nprogramming/erasing cycles). The results, shown in Figure R3-12a, indicate a slight\nthreshold voltage shift from -12 V to -13 V and a marginal reduction in the on-state\ncurrent when compared to the initial state. Nevertheless, the I /I ratio remains above\non off\n10⁸, demonstrating that repeated programming operations have a minimal impact on\ndevice performance. As shown in the Figure R3-12b, the leakage currents before and\nafter 9000 pulses are both maintained at around 10-14 A. These results demonstrate that\nthe device performance shows negligible degradation after 9000 pulse operations,\nsuggesting the high stability of the Sb O Cl single-crystal dielectric layer. To reflect\n4 5 2\nthe reviewer’s concerns, we have added the new experimental results in Supplementary\nFig. 32, and the related description in lines 15-17, page 13 of the revised main text.\nFigure R3-12. Transfer characteristics (a) and leakage currents (b) of device before\nand after 9000 programming pulses.\nQ7. Can the dielectric be integrated into scalable device platforms with channel lengths\nbelow 100 nm?\nResponse: Thanks for your kind suggestions. We have successfully fabricated a 3×3\narray of MoS FETs based on Sb O Cl ionic single-crystal dielectric layers with ~90\n2 4 5 2\nnm channel. The transfer characteristic curves of devices are shown in Figure R3-13.\nThe device exhibits an average on/off ratio of ~10⁷, demonstrating the potential of\nSb O Cl for application in short-channel scalable device platforms.\n4 5 2\nFigure R3-13. Transfer characteristic curves of a 3x3 array device with ~90nm\nchannel\nQ8. Can a basic logic or memory function be demonstrated to support claims of\nmultifunctionality?\nResponse: Thanks for your kind suggestions. To support claims of multifunctionality,\nwe have fabricated and tested logic inverter devices based on Sb O Cl ionic single-\n4 5 2\ncrystal dielectric layers, as shown in Figure R3-14. Furthermore, we successfully\nimplemented logic functions, as shown in Figure R3-15. The full device consists of two\nMoS n-type transistors and two MoTe p-type transistors; Figures R3-15a and b\n2 2\npresent the optical microscope image and circuit schematic, respectively. The\ncorresponding AND and NAND logic functions are demonstrated in Figures R3-15c\nand d. The realization of these functional applications confirms the promising prospects\nof Sb O Cl ionic single-crystal dielectric layers in the field of 2D multifunctional\n4 5 2\nelectronic devices.\nMoreover, leveraging the Cl⁻-ion-mediated conductivity modulation of MoS in\n4 5 2 2 4 5 2\nfunctionality, as shown by the test results in Figures R3-16. The successful\nimplementation of these logic and memory applications further validates the potential\nof Sb O Cl ionic single-crystal dielectric for use in multifunctional 2D electronic\n4 5 2\ndevices. To reflect the reviewer’s concerns, we have added the new experimental results\nin Supplementary Fig. 16, 17, and 20, and included relevant descriptions in lines 10-\n16 on page 8 and lines 13-16 on page 9 of the main text.\nFigure R3-14. Logic inverter based on Sb O Cl . a, Circuit diagram (upper) and\n4 5 2\noptical image of a typical complementary inverter composed of MoS and MoTe FETs\n2 2\nbased on Sb O Cl crystal dielectric. Scale bars, 10 μm. b, The voltage transfer\n4 5 2\ncharacteristics of the inverter as a function of the input voltage with different V from\nDD\n0.5 to 3V. c, The corresponding voltage gains of the resulting inverter.\nFigure R3-15. Logic functions based on Sb O Cl . a, Optical image of logic device\n4 5 2\ncomposed of MoS and MoTe FETs based on Sb O Cl crystal dielectric. Scale bars,\n2 2 4 5 2\n10 μm. b, Circuit diagram of AND and NAND gates. c, Input–output logic functions of\nthe AND gate with an V of 2 V. d, Input–output logic functions of the NAND gate with\nDD\nan V of 2 V.\nDD\nFigure R3-16. Memory function based on MoS /Sb O Cl /FLG back-gated FETs. a,\n2 4 5 2\nSchematic diagram of the device structure and optical microscope image. Scale bars,\n10 μm. b, Transfer curves under different control gate voltages. c, Memory window\nwidth as a function of maximum control gate voltage, V . d, Retention of device. The\ng, max\nretention is measured by applying a V pulse of −15 V (red) or +15 V (blue). Pulse\nionic\nwidth is 400ms. e, Endurance characteristics of device. Switching between the erase\nstate (red) and the program state (blue) is realized by changing the sign of the V\nionic\npulse. Pulse amplitude is 15 V, and pulse width is 400 ms.\nMinor Comments and Clarifications:\nQ1. The term *“biomimetic”* used in the context of neuromorphic image processing\nis overstated. Since there is no biological interfacing or experimentally validated\nmimicry of neural functions, the term should be replaced with *“bio-inspired”* or\nqualified appropriately.\nResponse: Thanks for your kind suggestions. By following the reviewer’s suggestion,\nwe have reviewed the manuscript and replaced all instances of the word \"biomimetic\"\nwith \"bio-inspired\" (line11, page 2 and line11, page 4 of the main text).\nQ2. Please clarify whether the reported ultralow leakage current remains stable after\nrepeated modulation cycles or environmental exposure.\nResponse: Thanks for your kind suggestions. We compared the transfer\ncharacteristic curves of the FETs before and after 9,000 pulse operations (equivalent\nto 45 programming/erasing cycles). These results, shown in Figure R3-17, demonstrate\nthat the device performance shows negligible degradation in I /I ratio (108) and\non off\nleakage current (10-14 A) after 9000 pulse operations, suggesting the high stability of\nthe Sb O Cl ionic single-crystal dielectric layer. To reflect the reviewer’s concerns, we\n4 5 2\nhave added the new experimental results in Supplementary Fig. 32, and the related\ndescription in lines 15-17, page 13 of the revised main text.\nFigure R3-17. Transfer characteristics (a) and leakage currents (b) of device before\nand after 9000 programming pulses.\nQ3. The device architecture includes both top and bottom gates. A clearer of their\nrespective roles and independent control during modulation experiments would be\nhelpful.\nResponse: Thanks for your kind suggestions. In the MoS /Sb O Cl /FLG FETs, the\n2 4 5 2\nSb O Cl layer functions as a back-gate dielectric, leveraging its high dielectric\n4 5 2\nconstant (primarily from ionic polarization). In the dual-gate Sb O Cl /MoS /SiO /Si\n4 5 2 2 2\ndevice, however, Sb O Cl operates primarily as a functional/regulatory layer. The\n4 5 2\nionic gate voltage (V ) controls Cl⁻ migration within Sb O Cl to modulate the MoS\nionic 4 5 2 2\ncarrier concentration, and the modulated electrical behavior of MoS₂ is subsequently\nprobed via back-gate FETs measurements. Thus, the latter exploits the carrier-\nmodulation capability enabled by ion migration in Sb O Cl , rather than its dielectric\n4 5 2\nproperty. To reflect the reviewer’s concerns, we have added and the related explanation\nin lines 22-26, page 8 of the revised main text.\nQ4. Can the dielectric thickness be scaled below 100 nm while maintaining the\ndielectric strength and performance?\nResponse: Thanks for your kind suggestions. We successfully fabricated a\nmolybdenum MoS₂ transistor using a 68-nm-thick Sb O Cl as the dielectric. The\n4 5 2\nmeasurement results (Fig. R3-14) demonstrate that the device maintains a high on/off\nratio of 10⁸ and a mobility of 17.5 cm²/V·s with V = 1V, indicating favorable electrical\nds\nperformance. These results suggest Sb O Cl below 100 nm can maintain the dielectric\n4 5 2\nstrength and performance. To reflect the reviewer’s concerns, we have added the new\nexperimental results in Supplementary Fig. 14, and the related description in lines 1-4,\npage 8 of the revised main text.\nFigure R3-18. Sb O Cl /MoS top-gated FETs with the thickness of Sb O Cl below\n4 5 2 2 4 5 2\n100 nm. a, optical microscope image of device. b, AFM image and the corresponding\nheight profile of Sb O Cl nanosheet in a. c, Transfer characteristics of the device.\n4 5 2"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have adequately addressed all questions and comments raised and incorporated necessary revisions into the manuscript. I recommend accepting the work for publication in Nature Communications.", "reviewer_2": "The authors have basically answered my questions, and I agree that the current version can be published in Nature Communications.", "reviewer_3": "The reviewer wants to thank the authors for their detailed comments and careful revision of their work. There are not further comments."}, "author_response": ""}]

Decision letter