The development of hafnia-based ferroelectric memory necessitates careful balancing of retention time and switching endurance-both critically dependent on operating voltage. While lower voltages naturally reduce power consumption and increase endurance, they induce partial polarization switching (polydomain states), whose retention properties remain poorly understood. This challenge is compounded by the industry's requirement for 10-year retention, which cannot be directly measured. Here we establish a physics-based framework predicting polarization loss in polydomain Hf0.5Zr0.5O2 capacitors under lowvoltage operation. Time-resolved I-V analysis reveals opposing imprint effects in domains with upward (P up arrow) and downward (P down arrow) polarization, manifested as peak splitting in switching currents. This behavior drives retention degradation through two distinct mechanisms: progressive domain inaccessibility as shifting coercive fields surpass read-voltage thresholds, and polarization backswitching during read operations due to imprint-induced asymmetric switching. The proposed model predicts retention loss across arbitrary read voltages by correlating the time-dependent coercive-voltage evolution in the P up arrow domain and P down arrow domain populations that constitute the domain configuration established during the write operation. The framework demonstrates that read voltage dominates retention stability, providing essential design rules for memory optimization. These findings bridge fundamental domain dynamics with practical device engineering, advancing scalable ferroelectric memory development.

Low-voltage operation is widely used in hafnia-based ferroelectric memories to improve endurance and reduce power consumption, but it often leaves the ferroelectric film in a partially switched polydomain state with accelerated retention loss linked to splitting of switching current peaks. The underlying mechanisms, however, remain poorly understood. Here, we investigate the origin of switching current peak splitting in polycrystalline Hf0.5Zr0.5O2 (HZO) capacitors. Combining experiments and theory, we show that peak splitting arises from two factors: imprint acting on domain populations with opposite polarizations and grain-to-grain variations in switching kinetics. Measurements as a function of write voltage, delay time, and voltage sweep rate establish key constraints on the underlying mechanism: peak separation grows with aging time, exhibits a sweep-rate dependence indicative of charge emission during readout, and remains nearly independent of the fraction of switched domains. However, imprint alone cannot explain the smooth shape of the split peaks. To address this, we develop a stochastic switching model that combines Merz law kinetics, dead-layer-induced imprint, and statistical variations of switching parameters among individual HZO grains. The model reproduces the dependence of peak splitting on domain fraction, delay time, and sweep rate. Simulations show that peak separation is governed by the evolution of imprint-induced built-in fields, whereas the smooth peak shape originates from grain-to-grain variability. These results provide a physical understanding of imprint and retention loss in polydomain hafnia memories, aiding the optimization of low-voltage operation.

HfO2-based ferroelectrics offer exceptional silicon compatibility and scalability for next-generation nonvolatile memory, yet the fundamental role of mechanical stress in their functional properties remains unresolved. This study provides direct experimental and theoretical evidence that tensile stress intrinsically governs the ferroelectric and dielectric response of Hf0.5Zr0.5O2. Using a uniquely designed stretchable ferroelectric capacitor (W/ Hf0.5Zr0.5O2/TiN) on a polyimide substrate, we perform in situ measurements under controlled uniaxial tensile strain. Concurrent first-principles calculations simulate strain in the polar orthorhombic Pca2(1)HfO(2) phase. Both approaches conclusively demonstrate that switchable polarization monotonically decreases with strain, dielectric permittivity increases, leakage current reduces. These reversible trends are attributed to strain-induced rearrangement of the crystal structure (not electronic effects). In turn, domain reorientation and phase exchange are ruled out as the primary mechanism. Discrepancies in the absolute values between the experiment and the theory arise from polycrystallinity, interfacial tetragonal layers, and grain boundaries. Our findings resolve long-standing debates on stress-mediated ferroelectricity in HfO2, establishing that intrinsic lattice deformation-not extrinsic factors-primarily dictates property changes. This work enables precise stress engineering for HfO2-based electronic devices.

The development of low-power and high-density ferroelectric memories requires scaling the thickness of the functional layer. However, the thickness could have a significant impact on the performance of memory devices. This work examines the effect of ferroelectric layer thickness on resistive switching and depolarization phenomena in a metal-Hf0.5Zr0.5O2-Si (MFS) structure, which is the functional structure of both ferroelectric field-effect transistors (FeFETs) and ferroelectric tunnel junctions (FTJs). The MFS structures show one stable and another unstable polarization state, with the instability caused by the strong electric field produced by charged donor surface states at the Si interface and poor screening of this polarization. The rate of the unstable state depolarization slows down with increasing thickness from 5 to 10 nm, which is due to the decrease in the depolarization field at the same potential difference in the structure. The resistive effect increases with increasing thickness up to ROFF/RON = 24, which is related to the reduction of undesired conductivity along the grain boundaries of the polycrystalline Hf0.5Zr0.5O2 film. The temporal dynamics of the depolarization of the unstable polarization state and the resulting gradual switching off of the low-resistance state are close to the characteristic times of the weight change of biological synapses, and therefore, such ferroelectric memristors are suitable for emulating their behavior. The results may be useful for the development of building blocks for neuromorphic computing as well as a new generation of FeFET and FTJ-based memories.

Barium hexaferrite, Al substituted BaFe12-xAlxO19, Ti substituted BaFe12-xTixO19, and Al and Ti bisubstituted BaFe12-2xAlxTixO19 (with x = 0.0, 0.1, 0.5, and 1.0) were synthesized using a solid-phase method. The dopant content in the ceramics was controlled by its charge content. The effect of Al3+ or/and Ti4+ substitution on the crystal structure and properties of BaFe12-xAlxO19, BaFe12-xTixO19, and BaFe12-2xAlxTixO19 were studied. The phase purity and crystal structure of the ferrite solid solutions were studied by powder X-ray diffraction. Our investigation of the crystal structure confirmed the formation of a hexagonal single phase with space group P6(3)/mmc (194) in the synthesized samples. In all Al-substituted samples, smaller Al ionic radii decreased cell parameters. In the other samples, aliovalent Ti4+ substitution might be due to the formation of Fe2+, decreased parameter a, and increased parameters c and V. The magnetization of all the samples was saturated at room temperature in fields of similar to 3 T. The magnetization decreases for all samples. The coercivity decreased for BaFe12-xAlxO19 and for BaFe12-2xAlxTixO19, it decreased likely due to changing the crystalline particle sizes. An increasing amount of dopants resulted in a monotonous reduction of the Curie temperature (T-C). It was established for the first time that bisubstitution change the magnetic properties to values more significantly than the changes resulting from single cation substitution. By measuring room-temperature THz-IR spectra of real and imaginary permittivity, the doping effect on IR phonons and THz absorption was studied and compared with similar experiments performed for crystalline samples. The initial matrix cation substitution leads to the broadening of infrared phonon resonances. The effect is assigned to the charge-compensatory mechanisms in the compounds. Below a frequency of approximate to 5 cm(-1), we discovered clear signatures of relaxation-type absorption, whose origin could be related to the disordered character of the ceramic samples. As result, it can be concluded that the structure and properties of initial matrix with a magnetoplumbite structure can be controllably optimized for electronics devices applications by Al3+ or/and Ti4+ substitution.

Artificial synapse is a key element of future brain-inspired neuromorphic computing systems implemented in hardware. This work presents a graphene synaptic transistor based on all-technology-compatible materials that exhibits highly tunable biorealistic behavior. It is shown that the device geometry and interface properties can be designed to maximize the memory window and minimize power consumption. The device exhibits a virtually continuous range of multiple conductance levels, similar to synaptic weighting, which is achieved by gradual injection/emission of electrons into the floating gate and interface traps under the influence of an external electric field. Similar to the biological synapse, the transistor has short-term intrinsic dynamics that affects the long-term state. The temporal injection/emission dynamics of an electronic synapse closely resembles those of its biological counterpart and is exploited to emulate biorealistic behavior using a number of synaptic functions, including paired-pulse facilitation/depression, spike-rate-dependent plasticity, and others. Such a synaptic transistor can serve as a building block in hardware artificial networks for advanced information processing and storage.

Ferroelectric polycrystalline hafnium oxide films hold great promise for the electronics industry, though an understanding of ferroelectricity in this unconventional material is still lacking. Here, by an in situ synchrotron X-ray microdiffraction experiment, we reveal an important role of reversible and irreversible ferroelastic switching in the mechanism of polarization reversal in a 10 nm thick Hf0.5Zr0.5O2 film and in the origin of the so called wake-up effect consisting in a gradual increase in the remanent polarization of as-prepared memory structures. During the wake-up, the oblique polar axis irreversibly rotates in some ferroelectric orthorhombic grains and becomes more vertical on average in the film, which is the mechanism of the increase in measured polarization. This effect originates from the tensile stress emerging in the film during crystallization annealing and its gradual decrease via the rearrangement of the crystal lattice, which is consistent with first-principles calculations. In the woken-up structures, the polar axis also rotates during polarization switching, but reversibly, which means a different crystal structure of Hf0.5Zr0.5O2 in the upward and downward polarization states and breaking the inversion symmetry. The results provide insight into fundamentals of ferroelectric hafnium oxide and points the way for intelligent material engineering in the field of ferroelectrics-based devices.

Scalability down to several nanometers is recognized as one of the main advantages of ferroelectric hafnium oxide films, because this property of the functional material is vital for the implementation of high-density and low-power ferroelectric memory. The reduction in energy consumption during thickness scaling occurs due to the reduction in coercive voltage, which determines the required operating voltage of the memory chip. However, this phenomenon is accompanied by an increase in leakage currents, which has the opposite effect. This work reveals the origin of leakage currents in ferroelectric Hf0.5Zr0.5O2 films and their increase when the films are scaled from 10 to 5 nm through a combination of experimental techniques and theoretical calculations. Analysis of possible current transport mechanisms, spatial current distribution obtained by conductive atomic force microscopy, grain size measured by scanning electron microscopy, phase composition established by X-ray diffraction and the band gap of the Hf0.5Zr0.5O2 structural polymorphs calculated using density functional theory shows that the dominant contribution to current transport comes from grain boundaries containing multiple charge carrier traps. In-plane and out-of-plane trap densities increase with decreasing thickness due to grain size reduction and redox reactions with electrode materials. These insights provide actionable guidelines for engineering HZO films and interfaces to suppress leakage, a pivotal advancement toward realizing scalable, energy-efficient ferroelectric memory technologies.

Aluminum substituted BaFe12-xAlxO19, titanium substituted BaFe12-xTixO19, aluminum and titanium substituted BaFe12-x-yAlxTiyO19 (with x = y = 0.0, 0.1, 0.5, 1.0) barium hexaferrites have been synthesized using the solid phase method. The effect of Al+3 or/and Ti4+ substitution on crystal structure and properties of BaFe12-xAlxO19, BaFe12-yTiyO19 and BaFe12-x-yAlxTiyO19 was studied. It was found that the resulting samples consist of plate-like hexagonal particles with sizes in the range of 1-10 μm. The phase purity and the crystal structure of the obtained ferrite solid solutions have been studied by powder X-ray diffraction. The results of investigation the crystal structure confirmed the formation of a hexagonal single phase with space group P63/mmc (194) in the synthesized samples. In all samples smaller ionic radii aluminum decreased cell parameters. On the other hand, aliovalent Ti4+substation due to the possibility of Fe2+ formation led decreased cell parameters. Magnetization for all the samples is saturated at room temperature in fields of ~ 3 T. The magnetization decreases from for all samples. The coactivity decreased for BaFe12-xAlxO19 and decreased for BaFe12-x-yAlxTiyO19 more likely due to changing the crystalline particle sizes. The Curie temperature decreased, which was due to a change in the magnetic structure of the resulting ferrite-based solid solutions.

Abstract Next‐generation flexible electronics for healthcare applications require biocompatible flexible non‐volatile memory for data storage. Ultra‐thin ferroelectric hafnium oxide films offer great potential for flexible memories due to their potential flexibility and perfect compatibility with modern technologies. This study presents ultra‐flexible and stretchable memory devices based on 10‐nm‐thick Hf0.5Zr0.5O2 film fabricated by an innovative technology involving encapsulation of the devices in a biocompatible organic package. They exhibit high memory functionality (remanent polarization of 27 µC cm−2) and withstand extreme mechanical conditions, including folding in half, multiple bending up to 150 000 bending cycles as well as tension with loads up to 1.5 kg. Further, flexible devices are employed as a platform to elucidate the fundamental role of mechanical stress in ferroelectricity of hafnia both experimentally and theoretically. Direct in situ experiment demonstrates that in‐plane tension causes changes in spontaneous polarization, coercive voltage, permittivity, and conductivity. First‐principle calculations explain the role of mechanical stress in ferroelectric and dielectric properties of hafnia. In applications, this work establishes a foundation for the implementation of biocompatible, high‐performance flexible ferroelectric memory, and in the field of ferroelectric materials fundamentals, it provides insight into the critical role of the residual mechanical stress that is inevitably present in thin films.

In the presented work, the method of metal-organic chemical vapor deposition (MOCVD) using Mo(CO)6 and H2S assisted by oxidative etching with water vapor, was employed for the synthesis of MoS2. This study was aimed at detailed investigation of the films' properties obtained via this method and identifying methods for elimination of such disadvantages as the carbon impurities and the small size of crystalline domains in the films. It was found that in the temperature range from 850 degrees C to 950 degrees C, the effect of water vapor on the morphology of MoS2 is significantly different. The study of the chemical states of molybdenum and sulfur made it possible to associate the size of the crystal domains formed with the efficiency of removing the oxidized states of Mo6+ and S6+. It is assumed that the increase in the domains' size is due to rapid lateral growth, resulting from the complete removal of the oxidized states at the edges, as well as a decrease in the density of nucleation centers due to the etching of less stable seeds on the substrate surface.

Polycrystalline aluminum substituted barium hexaferrite BaFe11AlO19 synthesized by the ceramic technique. The results of energy dispersive X-ray analysis, thermal X-ray diffraction (XRD), neutron diffraction, Mössbauer spectroscopy, magnet properties measurements were measured. XRD analysis demonstrated P63/mmc hexagonal structure of BaFe11AlO19. The magnetic sublattice of barium hexaferrite BaFe11AlO19 was obtained using neutron diffraction data. The distribution of aluminum in barium hexaferrite matrix at positions 2a and 12k was obtained with Mössbauer spectroscopy. A comparison of the calculated intensities of the neutronograms and the actual ones allowed us to establish that in position 2a the aluminum ion occupied a position with the coordinate (1;1;0), and the position of the substituent ion in position 12k (0.83333; 0.66667; 0.10810). According to neutron diffraction data, it was found that the actual Curie temperature is lower than that measured by differential scanning calorimetry.

Ferroelectricity is in demand in many device concepts in electronics, energy and microsystem engineering. The performance of ferroelectrics-based devices is determined by either out-of-plane or in-plane polarization, or out-of-plane or in-plane piezoelectric strain. Real prospects for the practical implementation of innovative devices opened up after the discovery of ferroelectricity in ultrathin hafnium oxide films, due to their perfect compatibility with silicon technology. Ferroelectric properties of this material have been assigned to an orthorhombic structural phase with a single polar axis, but the spatial orientation of the polarization vector and the tensorial piezoelectric behaviour, which are inextricably coupled, still remain unknown. Herein, the rotation of the polarization vector in a Hf0.5Zr0.5O2 (10 nm) capacitor during polarization switching and the spatial distribution of longitudinal and shear piezoelectric coefficients are elucidated at the nanoscale using operando vector piezoresponse force microscopy. In most of the capacitor, a 180 degrees-flipping of the polarization vector is observed, which is consistent with the orthorhombic phase structure. However, a rather large fraction of the capacitor is also occupied by nanoregions of ferroelastic (non-180 degrees) switching, which is explained by the effect of the local mechanical stress. To quantify the three-dimensional piezoresponse, a novel approach exploiting the Poisson effect in artificially created non-ferroelectric regions is proposed and it shows that the shear piezoelectric coefficient is twice the longitudinal coefficient. The experimental insights entail an important step in fundamental understanding of the ferroelectric and piezoelectric properties of hafnium oxide and have great potential to trigger new versions of ferroelectric-based devices.

Barium hexaferrite, Al substituted BaFe12-xAlxO19, Ti substituted BaFe12-xTixO19, and Al and Ti bisubstituted BaFe12-2xAlxTixO19 (with x = 0.0, 0.1, 0.5, and 1.0) were synthesized using a solid-phase method. The dopant content in the ceramics was controlled by its charge content. The effect of Al3+ or/and Ti4+ substitution on the crystal structure and properties of BaFe12-xAlxO19, BaFe12-xTixO19, and BaFe12-2xAlxTixO19 were studied. The phase purity and crystal structure of the ferrite solid solutions were studied by powder X-ray diffraction. Our investigation of the crystal structure confirmed the formation of a hexagonal single phase with space group P63/mmc (194) in the synthesized samples. In all Al-substituted samples, smaller Al ionic radii decreased cell parameters. In the other samples, aliovalent Ti4+ substitution might be due to the formation of Fe2+, decreased parameter a, and increased parameters c and V. The magnetization of all the samples was saturated at room temperature in fields of ~ 3 T. The magnetization decreases for all samples. The coercivity decreased for BaFe12-xAlxO19 and for BaFe12-2xAlxTiхO19, it decreased likely due to changing the crystalline particle sizes. An increasing amount of dopants resulted in a monotonous reduction of the Curie temperature (TC). It was established for the first time that bisubstitution change the magnetic properties to values more significantly than the changes resulting from single cation substitution. By measuring room-temperature THz-IR spectra of real and imaginary permittivity, the doping effect on IR phonons and THz absorption was studied and compared with similar experiments performed for crystalline samples. The initial matrix cation substitution leads to the broadening of infrared phonon resonances. The effect is assigned to the charge-compensatory mechanisms in the compounds. Below a frequency of ≈ 5 cm-1, we discovered clear signatures of relaxation-type absorption, whose origin could be related to the disordered character of the ceramic samples. As result, it can be concluded that the structure and properties of initial matrix with a magnetoplumbite structure can be controllably optimized for electronics devices applications by Al3+ or/and Ti4+ substitution.

Nonvolatile ferroelectric memory based on hafnium oxide thin films combines low power consumption, high speed, and record endurance. However, the commercialization of such memory is constrained due to the limited information retention time caused by the change in coercive voltage over time. Many efforts are under way to slow down this effect by material and interface engineering, and their results are being evaluated by comparison of the switchable polarization and coercive voltages at the time of writing information and reading it after a certain storage time. However, the real-life scenarios of a memory cell are much-more complex than a simple write-store-read cycle. Coercive voltages evolve over the whole lifetime of the memory cell, and read failure can occur in subsequent stages. In this work, we propose a predictive model for calculating the evolution of coercive voltages under any scenario of memory-cell lifetime. In particular, it takes into account multiple write-store-read-rewrite (both to the same state and to the opposite state) cycles, temperature fluctuations to which the memory chip is inevitably subjected, the influence of the selected operating frequency, and the procedure for recovery of the memory cell after its aging by a series of bipolar pulses, which is considered by memory designers as one of the options for increasing the retention time. The model is based on the polarization-switching dynamics described by the Landau-Khalatnikov equation and the phenomenon of charge injection into interfacial traps under the action of both the applied field and the spontaneous polarization field. The injected charge induces an internal built-in electric field in the ferroelectric layer, and leads to a change in the total field and an apparent change in the coercive voltage. The calculation results are in agreement with the results of experiments simulating different real-life scenarios of a memory cell based on a 10-nm-thick Hf0.5Zr0.5O2 film. The proposed model could serve as an intelligent tool for both material engineering and memory-chip design, which entails a new step in the development of ferroelectric memory.

Since ultrathin ferroelectric HfO2 films can be conformally grown by atomic layer deposition even on complex three-dimensional structures, new horizons in the development of next-generation piezoelectric devices are opened. However, hafnium oxide has a significant drawback for piezoelectric applications: its piezoelectric coefficients are much smaller than those of classical materials currently used in piezoelectric devices. Therefore, new approaches to the development of high-performance piezoelectric devices based on exploiting the unique properties of HfO2 are of paramount importance. In this work, a giant electromechanical effect in miniature piezoelectric membrane devices based on a 10 nm-thick ferroelectric Hf0.5Zr0.5O2 (HZO) film is experimentally demonstrated. Compared to the pure piezoelectric effect in the HZO film, the gain of the electromechanical response in membrane devices reaches 25 times. Numerical simulations confirm that this effect stems from the asymmetric shape of the membranes and can be further improved by designing the device geometry. Furthermore, according to first-principles calculations, an additional opportunity to improve the piezoelectric coefficient, and hence, the device efficiency is provided by the engineering of the mechanical stress in the HZO film. The proposed approach enables the development of new promising piezoelectric devices including miniature reflectors, nanoactuators, and nanoswitches.

The development of the new generation of non-volatile high-density ferroelectric memory requires the utilization of ultrathin ferroelectric films. The most promising candidates are polycrystalline-doped HfO2 films because of their perfect compatibility with silicon technology and excellent ferroelectric properties. However, the remanent polarization of HfO2 films is known to degrade when their thickness is reduced to a few nanometers. One of the reasons for this phenomenon is the wake-up effect, which is more pronounced in the thinner the film. For the ultrathin HfO2 films, it can be so long-lasting that degradation occurs even before the wake-up procedure is completed. In this work, an approach to suppress the wake-up in ultrathin Hf0.5Zr0.5O2 films is elucidated. By engineering internal built-in fields in an as-prepared structure, a stable ferroelectricity without a wake-up effect is induced in 4.5 nm thick Hf0.5Zr0.5O2 film. By analysis of the functional characteristics of ferroelectric structures with a different pattern of internal built-in fields and their comparison with the results of in situ piezoresponse force microscopy and synchrotron X-ray micro-diffraction, the important role of built-in fields in ferroelectricity of ultrathin Hf0.5Zr0.5O2 films as well as the origin of stable ferroelectric properties is revealed.

Metal-Organic CVD method (MOCVD) allows for deposition of ultrathin 2D transition metal dichalcogenides (TMD) films of electronic quality onto wafer-scale substrates. In this work, the effect of temperature on structure, chemical states, and electronic qualities of the MOCVD MoS2 films were investigated. The results demonstrate that the temperature increase in the range of 650 °C to 950 °C results in non-monotonic average crystallite size variation. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and Raman spectroscopy investigation has established the film crystal structure improvement with temperature increase in this range. At the same time, X-Ray photoelectron spectroscopy (XPS) method allowed to reveal non-stoichiometric phase fraction increase, corresponding to increased sulfur vacancies (VS) concentration from approximately 0.9 at.% to 3.6 at.%. Established dependency between the crystallite domains size and VS concentration suggests that these vacancies are form predominantly at the grain boundaries. The results suggest that an increased Vs concentration and enhanced charge carriers scattering at the grains’ boundaries should be the primary reasons of films’ resistivity increase from 4 kΩ·cm to 39 kΩ·cm.

Ferroelectric random access memory (FRAM) based on hafnium oxide is one of the most promising alternatives to modern nonvolatile flash memory. Despite a number of excellent performances, the commercialization of this memory is hindered by its limited retention time, which still does not meet the 10-year electronics-industry standard. A specific feature of the retention performance is that it cannot be measured directly, because 10 years is required to measure the actual polarization loss. In this work, we present a method for predicting polarization loss over information storage time that takes into account two physical phenomena affecting the information storage and readout: the emergence and temporal evolution of the internal built-in electric field in poled ferroelectrics (the imprint effect) and kinetics of polarization switching that determines the dependence of the switching speed on switching voltage. The method allows to calculate the retention loss for a wide range of operating voltages and frequencies.

Because of their full compatibility with CMOS technology, HfO2-based ferroelectrics, and especially Hf0.5Zr0.5O2 (HZO), attract a lot of attention. However, the overwhelming majority of measurement techniques provides only information about the cumulative electrical response of many domains of HZO, i.e., at the macroscopic level. So far, only piezoresponse force microscopy technique was applied to visualize distinct ferroelectric domains in HZO and to analyze the local switching behavior in the microscopic level. This work introduces the possibility of using electron beam-induced current (EBIC) technique in the scanning electron microscope to visualize the gradual polarization reversal of HZO and to obtain the local polarization dynamics. We show that although the local EBIC signal is affected by surrounding domains, studying the variations in the ferroelectric response of individual domains as well as the spread of the local stiffness and local imprint is possible by this method. Besides, we show the connection between the EBIC current and an electric field across passive non-ferroelectric layers at interfaces between HZO and metal electrodes, which opens up additional opportunities to use the EBIC technique for investigations of interface-dependent properties of HZO ferroelectrics in the future.