Ferroelectric Polarization State Research Articles

The electronic and magnetic properties modulated by ferroelectric polarization switching in two-dimensional VSeTe/Sc2CO2 van der Waals heterostructures.

Exploring multiferroic materials that combine magnetic and ferroelectric properties is scientifically interesting and has important technical implications for many functions of nanoscale devices. In this work, spintronics and magnetoelectric coupling devices are proposed in two-dimensional (2D) layered ferromagnetic (FM)/ferroelectric (FE) van de Waals (vdW) heterostructures, VSeTe/Sc2CO2, employing density functional theory (DFT) calculations. The results indicate that the VSeTe/Sc2CO2 vdW heterostructure changes from a metal to a semiconductor in Sc2CO2-P↑ and Sc2CO2-P↓ polarization states. At the same time, the charge at the interface of the VSeTe/Sc2CO2 heterostructure will also be redistributed with the transformation of the ferroelectric polarization state, resulting in the change of the distribution of the electronic states near the Fermi level, and thus the change in the magnetic anisotropy energy (EMAE) of the heterostructure. Interestingly, biaxial strain brings reversibility and non-volatile regulation to the heterostructure of semiconductors and metals. The results provide an effective way to fabricate magnetoelectric coupling devices with 2D multiferroic heterostructures.

Nonvolatile control of valley related properties and valley-contrasting transport in multiferroic van der Waals heterostructures

It is highly desirable to tune valley-related property through reversible and electrically nonvolatile methods. Taking the VSiGeP4/Al2S3 heterostructure as an example, we demonstrate that the valley splitting and valley-contrasting transport in VSiGeP4 monolayer are significantly enhanced by using a ferroelectric Al2S3 substrate. The vertical strain and electric field can modulate valley splitting, magnetic anisotropy, and magnetic ground state. The valley splitting is mainly governed by charge transfer between the two sublayers. The valley splitting and valley-contrasting transport are highly tunable when the ferroelectric polarization state of the Al2S3 substrate is the upward direction. In contrast, the valley splitting is rather robust when the ferroelectric polarization state is switched to the opposite direction. Furthermore, we propose to use electrical conversion between two opposite ferroelectric polarization states to obtain nonvolatile control of valley-related properties. Our research provides a proof-of-concept scheme to achieve electrical control based on multiferroic van der Waals heterostructures.

A Reconfigurable Ferroelectric Transistor as An Ultra‐Scaled Cell for Low‐Power In‐Memory Data Processing

AbstractCompact in‐memory computing architectures are desirable to embed artificial intelligence (AI) in resource‐restricted edge devices. However, current technologies face limitations in both the area and energy efficiency. Here, a reconfigurable ferroelectric tunnel field‐effect transistor (ferro‐TFET) is presented that can be used as an ultra‐scaled cell for low‐power in‐memory data processing. A gate‐all‐around ferroelectric film is integrated on a vertical nanowire TFET with a gate/source overlapped channel, enabling non‐volatilely reconfigurable anti‐ambipolarity by programming the ferroelectric polarization state. By considering the stored polarization state and reading voltage as inputs, an XNOR operation is achieved in a single‐gate ferro‐TFET. It is shown that the ferro‐TFETs can be implemented in a crossbar array for convolutional frequency filtering whose performance can be evaluated by an impulse‐response method considering the effect of device‐to‐device variation based on statistics. Benefiting from the miniaturized footprint, non‐volatility, and low‐power operation, ferro‐TFETs show promises as a one‐transistor in‐memory computing cell for area‐ and energy‐efficient edge AI applications.

2D Reconfigurable Memory Device Enabled by Defect Engineering for Multifunctional Neuromorphic Computing.

In this era of artificial intelligence and Internet of Things, emerging new computing paradigms such as in-sensor and in-memory computing call for both structurally simple and multifunctional memory devices. Although emerging two-dimensional (2D) memory devices provide promising solutions, the most reported devices either suffer from single functionalities or structural complexity. Here, this work reports a reconfigurable memory device (RMD) based on MoS2/CuInP2S6 heterostructure, which integrates the defect engineering-enabled interlayer defects and the ferroelectric polarization in CuInP2S6, to realize a simplified structure device for all-in-one sensing, memory and computing. The plasma treatment-induced defect engineering of the CuInP2S6 nanosheet effectively increases the interlayer defect density, which significantly enhances the charge-trapping ability in synergy with ferroelectric properties. The reported device not only can serve as a non-volatile electronic memory device, but also can be reconfigured into optoelectronic memory mode or synaptic mode after controlling the ferroelectric polarization states in CuInP2S6. When operated in optoelectronic memory mode, the all-in-one RMD could diagnose ophthalmic disease by segmenting vasculature within biological retinas. On the other hand, operating as an optoelectronic synapse, this work showcases in-sensor reservoir computing for gesture recognition with high energy efficiency.

Out-of-Plane Ferroelectricity in Two-Dimensional 1T‴-MoS2 Above Room Temperature.

Two-dimensional (2D) molybdenum disulfide (MoS2), one of the most extensively studied van der Waals (vdW) materials, is a significant candidate for electronic materials in the post-Moore era. MoS2 exhibits various phases, among which the 1T‴ phase possesses noncentrosymmetry. 1T‴-MoS2 was theoretically predicted to be ferroelectric a decade ago, but this has not been experimentally confirmed until now. Here, we have prepared high-purity 2D 1T‴-MoS2 crystals and experimentally confirmed the room-temperature out-of-plane ferroelectricity. The noncentrosymmetric crystal structure in 2D 1T‴-MoS2 was convinced by atomically resolved transmission electron microscopic imaging and second harmonic generation (SHG) measurements. Further, the ferroelectric polarization states in 2D 1T‴-MoS2 can be switched using piezoresponse force microscopy (PFM) and electrical gating in field-effect transistors (FETs). The ferroelectric-to-paraelectric transition temperature is measured to be about 350 K. Theoretical calculations have revealed that the ferroelectricity of 2D 1T‴-MoS2 originates from the intralayer charge transfer of S atoms within the layer. The discovery of intrinsic ferroelectricity in the 1T‴ phase of MoS2 further enriches the properties of this important vdW material, providing more possibilities for its application in the field of next-generation electronic devices.

Intrinsic valley-polarized quantum anomalous Hall effect in a two-dimensional germanene/MnI2 van der Waals heterostructure

Abstract Valley-polarized quantum anomalous Hall effect (VQAHE), combined nontrivial band topology with valleytronics, is of importance for both fundamental sciences and emerging applications. However, the experimental realization of this property is challenging. Here, by using first-principles calculations and modal analysis, we predict a mechanism of producing VQAHE in two-dimensional ferromagnetic van der Waals germanene/MnI2 heterostructure. This heterostructure exhibits both valley anomalous Hall effect and VQAHE due to the joint effects of magnetic exchange effect and spin–orbital coupling with the aid of anomalous Hall conductance and chiral edge state. Moreover interestingly, through the electrical modulation of ferroelectric polarization state in In2Se3, the germanene/MnI2/In2Se3 heterostructure can undergo reversible switching from a semiconductor to a metallic behavior. This work offers a guiding advancement for searching for VQAHE in ferromagnetic van der Waals heterostructures and exploiting energy-efficient devices based on the VQAHE.

Nonvolatile Modulation of Bi2O2Se/Pb(Zr,Ti)O3 Heteroepitaxy.

The pursuit of high-performance electronic devices has driven the research focus toward 2D semiconductors with high electron mobility and suitable band gaps. Previous studies have demonstrated that quasi-2D Bi2O2Se (BOSe) has remarkable physical properties and is a promising candidate for further exploration. Building upon this foundation, the present work introduces a novel concept for achieving nonvolatile and reversible control of BOSe's electronic properties. The approach involves the epitaxial integration of a ferroelectric PbZr0.2Ti0.8O3 (PZT) layer to modify BOSe's band alignment. Within the BOSe/PZT heteroepitaxy, through two opposite ferroelectric polarization states of the PZT layer, we can tune the Fermi level in the BOSe layer. Consequently, this controlled modulation of the electronic structure provides a pathway to manipulate the electrical properties of the BOSe layer and the corresponding devices.

Photo-controlled programmable logic gate via self-powered Cu2O/BiFeO3/TiO2 ferroelectric heterojunction photodetectors

The increased demands for high integration, fast computation, and a wide range of data processing in digital logic circuits have triggered an interest in programmable logic gates that can run different logic operations. Photodetectors (PDs) based on ferroelectric materials can obtain different ferroelectric polarization states utilizing pre-biased voltage regulation to achieve programmable logic functions, but low photoelectric conversion efficiency and slow photoresponse speed are still key problems to be addressed for programmable logic gate devices. Herein, the Cu2O/BiFeO3(BFO)/TiO2 ferroelectric heterojunction PDs were constructed by introducing a p-type hole transport layer Cu2O on the BFO/TiO2 ferroelectric heterojunction films, which not only broadens the photoresponse spectra range to the red light, but also forms a stepped energy band structure at the heterojunction interface, and the interfacial electric field promotes the separation and transport of photogenerated carriers, improving the self-powered photodetection performance of the devices. The Cu2O/BFO/TiO2 PDs demonstrate a responsivity of 3.0 mA/W and a photoresponse rise time/decay time of 2.3/23.9 ms at 420 nm light illumination. The Cu2O/BFO/TiO2 PD can be polarized in different states by pre-biased voltage and outputs different electrical signal values under the ultraviolet (365 nm) and visible (420 nm) monochromatic light or the mixed light irradiation, thus the device can realize the "AND" gate output in the positive bias polarization state and the "OR" gate output in the negative bias polarization state, which shows that the ferroelectric heterojunction PDs has a great potential application in the field of photo-controlled programmable logic gate circuits.

Computational study on ferroelectric control over spin polarization in the bipolar magnetic semiconductor

Multiferroic van der Waals (vdW) heterostructures offer an exciting route toward the nanoelectronics and spintronics device technology. How to realize the mutual regulation between ferroelectric and magnetic materials has attracted extensive research. In this work, based on the density functional theory, we simulate a vdW multiferroic heterostructure based on the bipolar magnetic semiconductor material graphone and ferroelectric monolayer In2Te3 and further investigate its electronic properties. We find that direct contact between In2Te3 and graphone induces a transition in graphone from a ferromagnetic state to a non-magnetic state. Fortunately, the magnetic properties of graphone are preserved by using graphene as an intercalation layer, and the graphone monolayer changes from its original semiconductor to a half-metal in the graphone/graphene/In2Te3 vdW heterostructure for P↓ state. Furthermore, by adjusting the layer spacing of the heterostructure, the spin polarization states of graphone at the Fermi level (EF) are regulated between spin-up (S↑) and spin-down (S↓) with the reversal of ferroelectric polarization states. Our results not only provide a promising way to realize the half-metallicity in 2D magnetic materials but also computationally predict the ferroelectric control of the spin polarization state, which has great application potential in the next-generation nonvolatile electrically controlled spintronic devices.

Homo‐type α‐In2Se3/PdSe2 Ferroelectric van der Waals Heterojunction Photodetectors with High‐performance and Broadband

AbstractTwo‐dimensional (2D) materials have attracted extensive attention in the field of photodetection thanks to their unique physical properties. Among them, the PdSe2 nanoflake shows great potential. However, the performance of the PdSe2‐based photodetector with a hetero‐type heterojunction remains poor due to the severe tunneling‐assisted interfacial recombination of photogenerated electron‐hole pairs in the thin bilateral‐depletion heterojunctions. In this work, a novel photodetector with a α‐In2Se3/PdSe2 homo‐type heterojunction for both high‐performance and broadband detection from visible to short‐wave infrared is constructed. The high‐performance of the photoresponsivity of 4.64 × 103 A·W−1, the external quantum efficiency of 1.08 × 106%, and the specific detectivity of 1.55 × 1014 Jones at 532 nm is the result of the homo‐type unilateral‐depletion junction which can promote the effective separation of photogenerated electron‐hole pairs compared to the hetero‐type. Also, adjusting the α‐In2Se3 ferroelectric polarization state further optimizes the unilateral depletion region. In addition, the photodetector can work in a self‐powered mode. This study suggests that the PdSe2‐based homo‐type device has great application potential in the field of 2D optoelectronics.

Artificial Optoelectronic Synapses Based on Light‐Controllable Ferroelectric Semiconductor Memristor

AbstractNumerous synaptic devices have been explored for the next generation of energy‐efficient computing techniques. Among them, optoelectronic synaptic devices based on semiconductor/ferroelectric heterostructures have received a lot of attention lately due to their amazing parallelism, efficiency, and fault tolerance properties. However, polarizing the ferroelectric layer or gating the dielectric layer is necessary to achieve tunable synaptic functions, which generally causes an increase in energy consumption and complex manufacturing processes. Here, a simple and efficient method is demonstrated to develop a tunable optoelectronic synaptic device based on a single ferroelectric semiconductor, BiFeO3‐BaTiO3 (BF‐BT). Multi‐essential synaptic functions including short‐term plasticity, paired‐pulse facilitation, and long‐term plasticity are all satisfactorily replicated by the memristor device. More significantly, light‐controllable synaptic behaviors are realized by altering the ferroelectric polarization state of BF‐BT. Synaptic devices’ relaxation characteristics enable simulation of the effects of positive/negative emotions on learning and forgetting processes. This study highlights the potential of the ferroelectric semiconductor memristor in constructing the efficient optoelectronic synapses for future neuromorphic electronics with the ability to learn and sense optical information.

Reliable Accessibility of Intermediate Polarization States in Textured Ferroelectric Al0.66Sc0.34N Thin Film

AbstractFerroelectric materials are promising candidates for neuromorphic computing synaptic devices due to the nonvolatile multiplicity of spontaneous polarization. To ensure a sufficient memory window, ferroelectric materials with a large coercivity are urgently required for practical applications in highly scaled multi‐bit memory devices. Herein, a remarkable reliability of intermediate ferroelectric polarization states is demonstrated in a textured Al0.66Sc0.34N thin film with a coercive field of 2.4 MV cm−1. Al0.66Sc0.34N thin films are prepared at 300 °C on Pt (111)/Ti/SiO2/Si substrates using a radio frequency reactive sputtering method. Al0.66Sc0.34N thin films exhibit viable ferroelectricity with a large remanent polarization value of >100 µC cm−2. Through the conventional current–voltage characteristics, polarization switching kinetics, and temperature dependence of coercivity, the reproducibility of multiple polarization states with apparent accuracy is attributed to a small critical volume (3.7 × 10−28 m3) and a large activation energy (3.3 × 1027 eV m−3) for nucleation of the ferroelectric domain. This study demonstrates the potential of ferroelectric Al1‐xScxN for synaptic weight elements in neural network hardware.

Direct observation of intrinsic room-temperature ferroelectricity in 2D layered CuCrP2S6

Multiferroic materials have ignited enormous interest owing to their co-existence of ferroelectricity and ferromagnetism, which hold substantial promise for advanced device applications. However, the size effect, dangling bonds, and interface effect in traditional multiferroics severely hinder their potential in nanoscale device applications. Recent theoretical and experimental studies have evidenced the possibility of realizing two-dimensional (2D) multiferroicity in van der Waals (vdW) layered CuCrP2S6. However, the incorporation of magnetic Cr ions in the ferroelectric framework leads to antiferroelectric and antiferromagnetic orderings, while macroscopic spontaneous polarization is always absent. Herein, we report the direct observation of robust out-of-plane ferroelectricity in 2D vdW CuCrP2S6 at room temperature with a comprehensive investigation. Modification of the ferroelectric polarization states in 2D CuCrP2S6 nanoflakes is experimentally demonstrated. Moreover, external electric field-induced polarization switching and hysteresis loops are obtained in CuCrP2S6 down to ~2.6 nm (4 layers). By using atomically resolved scanning transmission electron microscopy, we unveil the origin of the emerged room-temperature ferroelectricity in 2D CuCrP2S6. Our work can facilitate the development of multifunctional nanodevices and provide important insights into the nature of ferroelectric ordering of this 2D vdW material.

Quantized movement of magnetic skyrmions in moiré multiferroic heterostructures

Moir\'e superlattices made with van der Waals layers are an excellent platform for exploring a wide range of exotic and important physical phenomena. In this study, we used first-principles calculations and atomistic spin dynamics simulations to design a two-dimensional van der Waals $\mathrm{Mn}{\mathrm{S}}_{2}/\mathrm{CuIn}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$ multiferroic moir\'e heterosuperlattice with tunable skyrmions through magnetoelectric coupling. The inherent lattice mismatch between the two monolayers of $\mathrm{Mn}{\mathrm{S}}_{2}$ and $\mathrm{CuIn}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$ creates incommensurate moir\'e patterns, along with modulated magnetic anisotropy and emerging magnetic skyrmions in $\mathrm{Mn}{\mathrm{S}}_{2}$. The magnetic skyrmion in $\mathrm{Mn}{\mathrm{S}}_{2}$ is strongly influenced by magnetoelectric coupling and can be tuned by the ferroelectric polarization of $\mathrm{CuIn}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$. Furthermore, these magnetic skyrmions can be controlled by a pulsed current to move or freeze within the moir\'e period under different ferroelectric polarization states of the $\mathrm{CuIn}{\mathrm{P}}_{2}{\mathrm{S}}_{6}$ layer. Our work showcases a two-dimensional van der Waals moir\'e heterosuperlattice with magnetoelectrically tuned magnetic skyrmions, which establishes a foundation for designing future spintronic devices.

Nonvolatile Electrical Control and Reversible Gas Capture by Ferroelectric Polarization Switching in 2D FeI2/In2S3 van der Waals Heterostructures

Nonvolatile electrical control is the core of future magnetoelectric nanodevices. In this work, we systematically explore both the electronic structures and transport properties of multiferroic van der Waals (vdW) heterostructures consisting of a ferromagnetic FeI2 monolayer and a ferroelectric In2S3 monolayer using density functional theory and the nonequilibrium Green's function method. The results reveal that the FeI2 monolayer can be reversibly switched between semiconducting and half-metallic properties by nonvolatile control of the In2S3 ferroelectric polarization states. Correspondingly, the proof-of-concept two-probe nanodevice based on the FeI2/In2S3 vdW heterostructure exhibits a significant valving effect by modulating the ferroelectric switching. Moreover, it is also found that the preference of nitrogen-containing gases such as NH3, NO, and NO2 for adsorption on the surface of FeI2/In2S3 vdW heterostructures strongly depends on the polarization direction of the ferroelectric layer. In particular, the FeI2/In2S3 heterostructure shows reversible capture behavior for NH3. As a result, the FeI2/In2S3 vdW heterostructure-based gas sensor demonstrates high selectivity and sensitivity. These findings may open up a new route for the application of multiferroic heterostructures to spintronics, nonvolatile memories, and gas sensors.

Photoferroelectric All-van-der-Waals Heterostructure for Multimode Neuromorphic Ferroelectric Transistors.

Interface-driven effects in ferroelectric van der Waals (vdW) heterostructures provide fresh opportunities in the search for alternative device architectures toward overcoming the von Neumann bottleneck. However, their implementation is still in its infancy, mostly by electrical control. It is of utmost interest to develop strategies for additional optical and multistate control in the quest for novel neuromorphic architectures. Here, we demonstrate the electrical and optical control of the ferroelectric polarization states of ferroelectric field effect transistors (FeFET). The FeFETs, fully made of ReS2/hBN/CuInP2S6 vdW materials, achieve an on/off ratio exceeding 107, a hysteresis memory window up to 7 V wide, and multiple remanent states with a lifetime exceeding 103 s. Moreover, the ferroelectric polarization of the CuInP2S6 (CIPS) layer can be controlled by photoexciting the vdW heterostructure. We perform wavelength-dependent studies, which allow for identifying two mechanisms at play in the optical control of the polarization: band-to-band photocarrier generation into the 2D semiconductor ReS2 and photovoltaic voltage into the 2D ferroelectric CIPS. Finally, heterosynaptic plasticity is demonstrated by operating our FeFET in three different synaptic modes: electrically stimulated, optically stimulated, and optically assisted synapse. Key synaptic functionalities are emulated including electrical long-term plasticity, optoelectrical plasticity, optical potentiation, and spike rate-dependent plasticity. The simulated artificial neural networks demonstrate an excellent accuracy level of 91% close to ideal-model synapses. These results provide a fresh background for future research on photoferroelectric vdW systems and put ferroelectric vdW heterostructures on the roadmap for the next neuromorphic computing architectures.

What lies beneath? Investigations of atomic force microscopy-based nano-machining to reveal sub-surface ferroelectric domain configurations in ultrathin films

Multiferroic materials, encompassing simultaneous ferroelectric and ferromagnetic polarization states, are enticing multi-state materials for memory scaling beyond existing technologies. Aurivillius phase B6TFMO (Bi6TixFeyMnzO18) is a unique room temperature multiferroic material that could ideally be suited to future production of revolutionary memory devices. As miniaturization of electronic devices continues, it is crucial to characterize ferroelectric domain configurations at very small (sub-10 nm) thickness. Direct liquid injection chemical vapor deposition allows for frontier development of ultrathin films at fundamental (close to unit cell) dimensions. However, layer-by-layer growth of ultrathin complex oxides is subject to the formation of surface contaminants and 2D islands and pits, which can obscure visualization of domain patterns using piezoresponse force microscopy (PFM). Herein, we apply force from a sufficiently stiff diamond cantilever while scanning over ultrathin films to perform atomic force microscopy (AFM)-based nano-machining of the surface layers. Subsequent lateral PFM imaging of sub-surface layers uncovers 45° orientated striped twin domains, entirely distinct from the randomly configured piezoresponse observed for the pristine film surface. Furthermore, our investigations indicate that these sub-surface domain structures persist along the in-plane directions throughout the film depth down to thicknesses of less than half of an Aurivillius phase unit cell (˂ 2.5 nm). Thus, AFM-based nano-machining in conjunction with PFM allows demonstration of stable in-plane ferroelectric domains at thicknesses lower than previously determined for multiferroic B6TFMO. These findings demonstrate the technological potential of Aurivillius phase B6TFMO for future miniaturized memory storage devices. Next-generation devices based on ultrathin multiferroic tunnel junctions are projected.

Polarization enhanced photoresponse of InSe via 2D ferroelectric CuCrP2S6.

Two-dimensional CuCrP2S6 possesses significant potential for low-power non-volatile devices owing to its multiferroic properties. Nonetheless, comprehensive investigations regarding the modulation of CuCrP2S6 polarization for enhancing semiconductor photodetection capabilities and its potential applications in ferroelectric non-volatile devices are still relatively scarce. In this study, we present a novel, non-volatile, tunable photodetector engineered through the integration of a ferroelectric heterostructure comprising CuCrP2S6 and InSe. Our findings reveal that distinct ferroelectric polarization states of CuCrP2S6 exert varying modulation effects on the InSe photodetection performance. Notably, optimized results give a responsivity of 1839 A W-1 and a detectivity of 1.9 × 1012 Jones at a 300 nm wavelength, featuring a substantial 20.7-fold difference in responsivity between the two polarization states. This investigation underscores the immense potential of CuCrP2S6 in the development of non-volatile, multi-state optoelectronic devices.

The effect of switchable electronic polarization states on the electronic properties of two-dimensional multiferroic TMBr2/Ga2SSe2 (TM = V-Ni) heterostructures.

Multiferroic van der Waals (vdW) heterostructures (HSs) prepared by combining different ferroic materials offer an exciting platform for next-generation nanoelectronic devices. In this work, we investigate the magnetoelectric coupling properties of multiferroic vdW HSs consisting of a magnetic TMBr2 (TM = V-Ni) monolayer and a ferroelectric Ga2SSe2 monolayer using first-principles theory calculations. It is found that the magnetic orderings in the magnetic TMBr2 layers are robust and the band alignment of these TMBr2/Ga2SSe2 HSs can be altered by reversing the polarization direction of the ferroelectric layer. Among them, VBr2/Ga2SSe2 and FeBr2/Ga2SSe2 HSs can be switched from a type-I to a type-II semiconductor, which allows the generation of spin-polarized and unpolarized photocurrent. Besides, CrBr2/Ga2SSe2, CoBr2/Ga2SSe2 and NiBr2/Ga2SSe2 exhibit a type-II band alignment in reverse ferroelectric polarization states. Moreover, the magnetic configuration and band alignment of these TMBr2/Ga2SSe2 HSs can be further modulated by applying an external strain. Our findings suggest the potential of TMBr2/Ga2SSe2 HSs in 2D multiferroic and spintronic applications.

Robustly Stable Ferroelectric Polarization States Enable Long-Term Nonvolatile Storage against Radiation in HfO2-Based Ferroelectric Field-Effect Transistors.

The ferroelectric field-effect transistors (FeFETs) with HfO2-based ferroelectric layers in the gate stacks are emerging as one of the most promising candidates for the next-generation nonvolatile memory devices due to their scalability and compatibility with conventional Si technology. Moreover, owing to the high radiation hardness of the HfO2-based ferroelectric thin films, HfO2-based FeFETs have attracted great interest in the fields of radiation-hard (rad-hard) memory. However, the reliability of their memory states under irradiation, which represents the validity of the stored information, has not been investigated. Here, we focus on the impact of the total ionizing dose (TID) on erased and programmed states of HfO2-based FeFETs. The TID radiation (X-ray) characteristics of erased and programmed HfO2-based FeFETs are characterized using an on-site read operation. Both the erased and programmed states show robust stability under irradiation at a dose rate of 90 rad(Si)/s, and even at 230 rad(Si)/s, only the erased state shows a slight variation. The possible factors contributing to memory state degradation are discussed. Through the analysis of the threshold voltage shift and subthreshold swing evolution, as well as studies of ferroelectric polarization stability under radiation, it is revealed that the erased state degradation is caused by oxide-trapped charges rather than interface degradation or polarization switching. The physical mechanism of the difference in radiation-induced oxide-trapped charges buildup in programmed and erased FeFETs is analyzed to explain different TID radiation characteristics between them. Our work suggests that the HfO2-based FeFETs have great potential in radiation environment applications.