Ferroelectric Characteristics Research Articles

A Novel Ferroelectric Rashba Semiconductor.

Fast, reversible, and low-power manipulation of the spin texture is crucial for next generation spintronic devices like non-volatile bipolar memories, switchable spin current injectors or spin field effect transistors. Ferroelectric Rashba semiconductors (FERSC) are the ideal class of materials for the realization of such devices. Their ferroelectric character enables an electronic control of the Rashba-type spin texture by means of the reversible and switchable polarization. Yet, only very few materials are established to belong to this class of multifunctional materials. Here, Pb1- xGexTe is unraveled as a novel FERSC system down to nanoscale. The ferroelectric phase transition and concomitant lattice distortion are demonstrated by temperature dependent X-ray diffraction, and their effect on electronic properties are measured by angle-resolved photoemission spectroscopy. In few nanometer-thick epitaxial heterostructures, a large Rashba spin-splitting is exhibiting a wide tuning range as a function of temperature and Ge content. This work defines Pb1- xGexTe as a high-potential FERSC system for spintronic applications.

In-Situ Reflectance Absorption Infra-Red Spectroscopy (RAIRS) Study on ALD of HfO2 on TiN and Pt Electrodes

Ferroelectricity in hafnia fluoride analogues has been widely investigated for nonvolatile memory applications. Although ALD of HfO2 technology is enough mature for CMOS technology, hafnia-based ferroelectrics still suffer from major reliability issues such as relaxation, imprint, fatigue, and breakdown.1 These reliability characteristics are thought to be related to the interface conditions between the ferroelectric film and the electrode. Thus, many reports suggested routes to enhance reliability and ferroelectric characteristics by modifying the interface states of the metal-ferroelectric-metal (MFM) capacitors. Unfortunately, only few reports disclose direct observation on evolution of interface formation and its mechanism. Recently, it is reported that scaling down the ferroelectric hafnia-based films to a few nm range dramatically improves the MFM capacitors’ reliability where the series capacitance and surface effect dominate, making it crucial to understand the interface properties carefully.2 In this presentation, we perform In-situ characterization using reflectance absorption infrared spectroscopy (RAIRS) to monitor the surface reaction and interface formation while HfOx ALD using TDMA-Hf with various oxidation reactants, such as H2O, O3, and anhydrous H2O2. TiN and Pt bottom electrodes are investigated at 250 °C. The RAIRS results show that the initial exposure of the oxidant generates the most amount of oxidation on the TiN surface by showing Ti-O and TiN-O peaks which were not observed for the Pt substrate. Moreover, the Ti-O and TiN-O peak area increase versus the dosing time of oxidant was minimum for H2O, and O3 showed continuous peak increase even after 12 s exposure. Interestingly, for the H2O2 case, there was almost no peak increase in the Ti-O bond region like H2O, but the TiN-O and TiO-O peaks appeared after the first 3 s and saturated after 6 s exposure. Also, not only on the TiN substrate, the peak for O-O stretching was observed for the Pt substrate as well, indicating that the H2O2 generates self-limiting peroxide bonds on the surface with a minimum interface formation. This suppressed interface formation with superior film properties using H2O2 might be the reason behind the robust reliability of the H2O2-based HZO capacitor. We are going to report reliability characteristics in conjunction with interface evolution.Acknowledements: We thank to YEST and KEIT for supporting the project through ISTD Program (No.20010806). This work is also supported by GRC-LMD program (task#3001.001) through SRC. The BRUTE hydrogen peroxide was provided by RASIRC. Ozone generator for TMEICReferences 1 J. Mohan et al., ACS AELM, 4, 4 (2022). 2 K. Toprasertpong et al., ACS AMI, 14 (2022).

In-Plane Ferrielectric Order in van der Waals β'-In2Se3.

van der Waals ferroic materials exhibit rich potential for implementing future generation functional devices. Among these, layered β'-In2Se3 has fascinated researchers with its complex superlattice and domain structures. As opposed to ferroelectric α-In2Se3, the understanding of β'-In2Se3 ferroic properties remains unclear because ferroelectric, antiferroelectric, and ferroelastic characteristics have been separately reported in this material. To develop useful applications, it is necessary to understand the microscopic structural properties and their correlation with macroscopic device characteristics. Herein, using scanning transmission electron microscopy (STEM), we observed that the arrangement of dipoles deviates from the ideal double antiparallel antiferroelectric character due to competition between antiferroelectric and ferroelectric structural ordering. By virtue of second-harmonic generation, four-dimensional STEM, and in-plane piezoresponse force microscopy, the long-range inversion-breaking symmetry, uncompensated local polarization, and net polarization domains are unambiguously verified, revealing β'-In2Se3 as an in-plane ferrielectric layered material. Additionally, our device study reveals analogous resistive switching behaviors of different types owing to polarization switching, defect migration, and defect-induced charge trapping/detrapping processes.

Acoustic sensor based on a PVDF-TrFE/BTO composite structure with improved ferroelectric and piezoelectric properties

Ferroelectric composite structures of poly (vinylidene fluoride-co-trifluoroethylene)/ barium titanate (PVDF-TrFE/BTO) were prepared using a solvent casting method and altered using electrical and mechanical modes to improve their ferroelectric characteristics. The PFM and P-E loop analytic studies validated the enhanced ferroelectric and piezoelectric capabilities of the modified composite structures following mechanical stretching and electrical poling. The stretched and poled samples (PT-BT-s-p) were able to achieve a maximum saturated polarization of 5.98 µC/cm2 with suitable saturation loops and domain switching points. The presence of ferroelectric domains was further confirmed by the PFM amplitude and PFM phase graphs of the PT-BT-s-p composite structures. Furthermore, the suggested composite structure achieved a maximum piezoelectric coefficient (d33) value of 11 pC/N. Finally, a lab-scale experiment with a sound wave sensing application was performed and seen with superior outcomes with varying waveforms, amplitudes, and frequencies, making it a promising contender for future sensory devices.

Improved Polarization‐Retention‐Endurance in Hf0.5Zr0.5O2 Films by ZrO2 Capping via Electrostatic Effects

AbstractFerroelectric hafnia is one of the most promising materials for next generation of non‐volatile memory devices. Several strategies have demonstrated to be of interest to improve its functional properties. Interface engineering, realized by the introduction of additional layer in the capacitor structure, is demonstrated as a promising strategy. However, interface layers can have multiple implications, such as changes in the chemistry of the interfaces and an increase of depolarization field, whose effects are difficult to discriminate. The role of HfO2 and ZrO2 capping is explored on polarization, retention, endurance, and leakage properties of Hf0.5Zr0.5O2 epitaxial films. In HfO2 capped films, lower polarization is observed, and endurance and retention are also comparably worse than in ZrO2 capped films. Complementary under illumination ferroelectric characterization and capacitance measurements indicate a reduction of defects and interface capacitance contribution in ZrO2 capped films. For both cappings, the interfaces with the Hf0.5Zr0.5O2 layer are shown to be compositionally sharp and the phase of Hf0.5Zr0.5O2 (HZO) grains is replicated on the capping layer, indicating that electrostatic effects prevail and that the use of interface layers with high permittivity, here ZrO2, is crucial to favor good functional properties.

Studies on structural, dielectric, and ferroelectric features of lanthanum modified complex Bismuth Nickel Titanate ceramic

Lanthanum substituted Bismuth Nickel Titanate (BNTO) ceramic, that is, (Bi 0.8La0.2)(Ni0.5Ti0.5)O3 (abbreviated as BLNTO 20) was successfully synthesised by solid-state reaction technique. The phase formation of the ceramic compound was confirmed by the X-ray diffraction study. The FESEM micrograph depicts the homogeneous spreading of the dissimilar size grains on the surface of the compound. The dielectric characteristics of ceramic were observed by computing the dielectric outcome in selected range of frequency and temperature. The frequency/temperature dependent conductivity plots of the ceramic compound satisfy the universal Jonscher’s power law. P-E Loop tracer was used to study the ferroelectric nature, which suggests the possibility of enhanced ferroelectric behaviour of the compound. Therefore, based on the enhanced ferroelectric features due to La doping ceramic compound may have promising performance for further electronic device application.

Electrical, dielectric, and ferroelectric characteristics of Bi4Ti2.9Se0.1O12

The current communication addresses structural, impedance, conductivity, dielectric permittivity, tangent loss, and ferroelectric hysteresis of selenium doped bismuth titanate (Bi4Ti2.9Se0.1O12) synthesized by a solid-state reaction technique. XRD profile reveals the formation of orthorhombic unit cell structure (B2ab space group) in Bi4Ti2.9Se0.1O12. Partial doping of Se (10%) makes significant modifications in the electrical and dielectric characteristics, which are investigated over discrete frequencies (1 kHz–1 MHz) and temperatures (27–300 °C). The compound exhibits comparatively low value of the tangent loss at 1 MHz frequency. The ferroelectric hysteresis loop of the compound confirms the non-centrosymmetric arrangement of elements at room temperature, and the value of remanent polarization makes the compound suitable for memory applications.

Enhanced electrocaloric effect over a broad temperature range in lead‐free Na0.5Bi0.5TiO3‐based relaxor ferroelectrics via doping with Bi(Mg0.5Zr0.5)O3

AbstractWith an increasing demand for environmentally friendly refrigeration, the solid‐state refrigeration based on the electrocaloric effect (ECE) has been drawn extensive attention. It is a challenge to maintain a large adiabatic temperature change (∆T) over a broad temperature span. Herein, the authors designed and synthesised (0.74‐x) Na0.5Bi0.5TiO3‐0.06BaTiO3‐0.2SrTiO3‐xBi(Mg0.5Zr0.5)O3 (abbreviated as NBT‐xBMZ) (x = 0, 0.02, 0.04, 0.06 and 0.08) lead‐free relaxor ferroelectrics. Their microstructures, dielectric properties, ferroelectric properties, ECEs and the structure‐property relationships were investigated. Via doping with BMZ, an enhanced relaxor feature and a wider temperature range where multi‐phases coexist were achieved. The relaxor ferroelectric characteristics were illustrated using the Vogel‐Fulcher relation. The indirectly calculated ECE results showed that the optimal ΔT of 1.11 K was obtained for the x = 0.02 sample at 90°C and 70 kV/cm over a wide Tspan of 120°C, providing a potential ECE material. The direct ECE results procured using thermocouple indicated that the maximal ∆T of 2.14 K and ∆T/∆E of 0.31 K m/MV were achieved in the same sample at 70°C and 7 MV/m and the variation trend of ECE results was consistent with the indirect results. Moreover, the multi‐phases coexistent strategy can be extended to other materials system to generate a large ΔT over a wide temperature range.

Advances in P(VDF-TrFE) Composites: A Methodical Review on Enhanced Properties and Emerging Electronics Applications

Piezoelectric polymers are a class of material that belong to carbon–hydrogen-based organic materials with a long polymer chain. They fill the void where single crystals and ceramics fail to perform. This characteristic of piezoelectric polymers made them unique. Their piezoelectric stress constant is higher than ceramics and the piezoelectric strain is lower compared to ceramics. This study’s goal is to present the most recent information on poly(vinylidene fluoride) with trifluoroethylene P(VDF-TrFE), a major copolymer of poly(vinylidene fluoride) PVDF with piezoelectric, pyroelectric, and ferroelectric characteristics. The fabrication of P(VDF-TrFE) composites and their usage in a variety of applications, including in actuators, transducers, generators, and energy harvesting, are the primary topics of this work. The report provides an analysis of how the addition of fillers improves some of the features of P(VDF-TrFE). Commonly utilized polymer composite preparation techniques, including spinning, Langmuir–Blodgett (LB), solution casting, melt extrusion, and electrospinning are described, along with their effects on the pertinent characteristics of the polymer composite. A brief discussion on the literature related to different applications (such as bio-electronic devices, sensors and high energy-density piezoelectric generators, low mechanical damping, and easy voltage rectifiers of the polymer composite is also presented.

Structural, optical, dielectric, and ferroelectric properties in [formula omitted] ceramics prepared by a solvothermal reflux approach

Chromium (Cr3+) doped BaTi1−xCrxO3 (x = 0.0, 0.03, 0.06, and 0.09) ceramics were prepared by the solvothermal reflux approach. X-ray diffraction analysis confirmed the development of tetragonal structures with P4mm symmetry in the prepared samples. The SEM analysis showed that Cr3+ doping resulted in a microstructure that was dense, uniform, and had smaller grains. Surface chemical information and oxidation states were studied using X-ray photoelectron spectroscopy. The diffuse reflectance spectrum confirmed the effect of Cr3+ content on the direct optical bandgap of BaTi1−xCrxO3 samples which shifts from 3.21 eV to 2.73 eV with increasing Cr3+ content. Dielectric permittivity was found to increase in the low-frequency region with increasing Cr3+ doping content up to x = 0.06, while it decreased in the high-frequency region compared to an undoped sample. The observed behavior of permittivity might be explained in terms of the formation of oxygen vacancy defects and their effects on the polarization dynamics of the material. Moreover, the addition of Cr3+ doping had a strong effect on the ferroelectric characteristics, as seen by the formation of a pinched hysteresis loop, resulting in the improvement of energy storage properties. Based on the obtained results, the sample with x = 0.06 exhibited an enhancement of about 3.3 times in energy discharge density and 26 % in storage efficiency compared to the undoped sample. This might be due to a large difference between the values of maximum and remnant polarizations, reduced tangent loss, and a smaller grain size, which makes this material attractive for use in energy storage devices.

Structure, dielectric and ferroelectric Properties of (1-x)K0.5Na0.5NbO3 – xBi0.5Na0.5TiO3(0 ≤ x≤ 0.1) Solid Solution

In this study, we prepared lead-free (1-x)K0.5Na0.5NbO3 – xBi0.5Na0.5TiO3 ceramics (KNNBTx) with x = 0, 0.025, 0.05, 0.075, 0.1 using the conventional solid-state reaction method. Scanning electron microscopy analysis revealed dense ceramics with a notable decrease of the average grain size from 3 μm for x = 0–0.3 μm for x ≥ 0.050. X-ray diffraction pattern refinement unveiled that the pure KNN possessed an orthorhombic Amm2 symmetry. In contrast, the KNNBT0.100 composition displayed a tetragonal P4mm symmetry, while the KNNBT0.025 composition exhibited a monoclinic Pm symmetry, suggesting the stabilization of an intermediate phase between the orthorhombic and tetragonal symmetries for x = 0.025. Dielectric measurements indicated that the introduction of small cations in A and B sites of the KNN matrix induced a diffusive phase transition. According to the modified Curie–Weiss law (named also Uchino and Nomura function), the degree of diffuseness (γ) increased from γ = 1.45 to γ 1.74 with increasing x. Raman spectroscopy revealed a frequency upshift of the vibration modes along with broadening of the modes as the NBT composition increased, indicating increased structural disorder in the perovskite structure. Temperature-dependent Raman spectra exhibited the persistence of certain modes at higher temperatures due to the off-centering of cations at A and B sites, a result of the induced substitution-induced disorder in the KNN matrix. Temperature dependent of Raman modes’ frequency have shown substantial modifications at temperatures close to the critical temperatures identified by dielectric measurements. Ferroelectric measurements demonstrated that the incorporation of NBT into the KNN matrix led to significant alterations in the polarization and ferroelectric characteristics of the parent ceramic (pure KNN). As the NBT content increased, the remanent polarization decreased from 13.1 to 3.6 μC/cm2, and the P-E curves became pinched/distorted, indicating a disruption in the long-range order of KNN due to structural and grain size modifications.

Synthesis and characterization of lead free multidoped ferroelectric material: (Bi0.85Nd0.15)(Fe0.5Ti0.5)O3

The Nd and Ti doped bismuth ferrite compound (Bi0.85Nd0.15)(Fe0.5Ti0.5)O3 has been synthesized through a solid state reaction method. Its various properties, such as structural, dielectric and ferroelectric features were thoroughly investigated. The XRD analysis confirms the phase formation with monoclinic symmetry of the compound. The field effect scanning electron microscope (FE-SEM) micrograph/image shows the surface morphology and uniformly distributed grains over its surface. Energy dispersive X-ray (EDX) suggests the presence of all ingredients with appropriate purity (constituent elements are in well ratios of their atomic and weight percentage). Investigation of impedance and dielectric data was carried out in an extensive range of temperature and frequency. Prepared material data expose a significant improvement in the electrical and dielectric characteristics. Frequency dependent ac-conductivity diagram/plot of present material obeys Jonscher’s universal power law. The PE loop tracer study confirms the ferroelectric nature of the material. Present study offers several interesting features of the material for further device applications.

Molecular dipole regulated surface potential and ferroelectric characteristics in nanoconfined P(VDF-TrFE) architectures

Molecular dipole orientation is crucial to efficiently utilize the piezo- and ferroelectric polarization in polymers. Modern electronic applications of these polymer demand switching of dipoles with low voltage, which requires the dipole orientation to be perpendicular to the substrate (edge-on) rather than parallel (face-on). The 0D, 1D and 2D confinement of polymer architectures into nanoparticles, nanofibers, and thin films is a vital approach to control dipole orientation in ferroelectrics. Our findings show that for 1D (d33 ∼ 18 ± 2.2 pm/V) and 2D nanostructures (d33 ∼ 15 ± 1.5 pm/V) of poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)), the molecular dipoles are edge-on, whereas for 0D, the dipoles are face-on, which would govern the ferroelectric and piezoelectric behaviour of these confined structures. The subsequent observation concludes that altering the dipole orientation allows precise modulation of surface potential and work function. The work functions of the 0D, 1D and 2D nanostructures are 4.56 ± 0.03 eV, 4.93 ± 0.51 eV and 4.68 ± 0.18 eV, respectively. The tunability of surface potential opens up the possibility of utilizing these nanostructures in single-material triboelectric series. Density functional theory (DFT)-based computations substantially support these experimental findings. This study provides a thorough understanding of the effect of molecule dipole orientation on piezo- and ferroelectric properties of P(VDF-TrFE) nanostructures.

Examining the ferroelectric characteristics of aluminum nitride‐based thin films

AbstractThe discovery of ferroelectricity in AlN‐based thin films, including Al1‐xScxN and Al1‐xBxN, over the past few years has spurred great research interests worldwide. In this review, we carefully examined the latest developments for these ferroelectric films with respect to alloy composition, temperature, film thickness, deposition condition, and fatigue endurance by electric field cycling. Looking ahead, there is an urgent need to resolve the challenge of large current leakage faced by these films, which necessitates a combined efforts from both simulations and experiments to identify the root cause and eventually come up with engineering strategies to suppress such leakage. In addition, overcoming the thickness scaling challenge to push ferroelectric thin film down to a few nanometers for better device miniaturization will also be of great interest. Considering the somewhat unexpected discovery of AlN‐based thin films with potential ferroelectric application, we believe that it will be also rewarding to further explore other III‐V‐based semiconductor materials.

Dy/Sr‐codoped (K0.5Na0.5)NbO3 multifunctional transparent‐ferroelectric ceramics with adjustable white‐light emission

AbstractTraditional solid‐state luminescent materials (e.g., phosphors and microcrystalline glasses) have attracted extensive attention due to their high energy efficiency and long lifespan. However, their application scope is limited by complex compositions and manufacturing processes, as well as single‐function. In this study, solid‐state reaction was utilized to prepare transparent‐ferroelectric (K0.5Na0.5)NbO3 (KNN) ceramics by simply codoping with Dy3+ and Sr2+, providing possibilities for large‐scale production. Ceramics exhibit high optical transmittance, high‐quality white‐light emission and relaxor ferroelectric feature. Under irradiation of UV light, photochromic behavior occurring in the ceramics, resulting in modulating the optical performances, especially quality of emitted white light. Multifunctionality can expand latent applications of KNN‐based ceramics from white light‐emitting diodes to modulated optoelectronic devices.

Multilevel nonvolatile photomemory with long-term robust optical retention based on photoinduced depolarization

Ferroelectric memory is promising for implementing emerging information technologies, including digital storage and analog computing. Two-dimensional (2D) ferroelectric materials retain robust room-temperature ferroelectric characteristics at the single-layer limit, surpassing traditional ferroelectric materials. This characteristic enables further advancements in device miniaturization to meet the growing demand. Herein, we manufactured a metal–insulator–ferroelectric–semiconductor field-effect transistor (MIFSFET) using a 2D ferroelectric material (α-In2Se3), which displayed nonvolatile characteristics. Based on the mechanism of photoinduced depolarization in a ferroelectric semiconductor, the MIFSFET device can be used as a photomemory, capable of storing an optical image for up to 1000 s with minimal information loss and can achieve a multistate photoresponse induced by an optical pulse. Moreover, it can function as a ferroelectric memory, with an on/off ratio exceeding 106, endurance of above 3000 cycles, and stable retention. The proposed MIFSFET demonstrated excellent optical image sensing and memory functions, presenting a feasible approach for developing efficient visual systems in the future.

Piezoelectric properties of noncovalently functionalized 2D nanomaterials incorporated poly(vinylidene fluoride) nanocomposites

AbstractWe report here for the first time the role of noncovalently functionalized 2D nanomaterials on the ferroelectric and piezoelectric behavior of poly(vinylidene fluoride) (PVDF) nanocomposites. Graphene oxide (GO), expanded graphite (EG) and hexagonal boron nitride (h‐BN) were noncovalently modified via Li‐salt of 6‐amino hexanoic acid (Li‐AHA), denoted as m‐GO, m‐EG and m‐BN, in order to de‐agglomerate and de‐stack them, which were subsequently incorporated into the PVDF matrix via solution mixing, followed by compression molding. Simultaneously, PVDF nanocomposites with unmodified 0.08 wt% of 2D nanomaterials were also prepared using the same methodology. PVDF/m‐BN nanocomposite showed a higher extent of polar phase (~36%) associated with PVDF phase as compared to PVDF/m‐GO and PVDF/m‐EG nanocomposites. Further, the highest permittivity (~58 at 10−1 Hz) was achieved in PVDF/m‐BN nanocomposite, which was also reflected in higher remnant polarization (~61 nC/cm2) and a significantly higher d33 value (~53 pm/V). Moreover, a higher output peak to peak voltage (~13 V) was obtained for the sensor device fabricated from PVDF/m‐BN nanocomposite. Thus, the role of Li‐AHA‐modified 2D nanomaterials in improving the morphology, dielectric, ferroelectric, and piezoelectric characteristics of the PVDF nanocomposites was clearly established.

Effect of ferrite phase addition on Pb-Free multiferroic composite material for energy storage applications

Bulk composite ceramics exhibit promising potential as energy storage materials due to their strong ferroelectric characteristics. To lessen the use harmful Pb based material, multiferroic composite combining ferrite and perovskite ceramics with piezoelectric and ferroelectric traits, have gained prominence for high-efficiency energy systems such as ceramic capacitor. This study focuses on a dual-phase multiferroic ceramic composite, following the formula (1-x) Ba0.77Ca0.23TiO3 + xNi0.6Zn0.25La0.15Fe2O4 (x = 0.0, 0.1, 0.2, and 0.3), prepared via a solid-state reaction process. XRD analysis confirms the presence of cubic perovskite (BaTiO3) and cubic spinel ferrite (NZLFO) phases. SEM images depict uniform microstructures with sporadic pore formations, which decreased in grain size with ferrite addition. The P-E loops reveal relaxor ferroelectric behavior with near-zero remnant polarization (Pr), indicating its suitability as an energy storage medium. The highest energy density efficiency, approximately 54 %, was achieved at x = 0.1. The addition of more than 10 % ferrite significantly affects both the microstructure and energy storage properties.

Achieving high energy-storage performance of medium-entropy (Na0.25Bi0.25Ca0.25Sr0.25)TiO3 lead-free relaxor ferroelectric ceramic for pulsed power capacitor

Advanced electrostatic energy-storage science and technology based on dielectric ceramics capacitors are widely applied in pulsed power systems. Recently, entropy increasing design engineering has been considered as an available method to promote electrical characteristics in dielectric energy-storage ceramics. In this study, medium-entropy (Na0.25Bi0.25Ca0.25Sr0.25)TiO3 (NBCSTO) ceramics with good energy-storage properties were obtained by a conventional solid-state reaction method. The microstructure and element analysis results show that a perovskite structure was identified for the NBCSTO sample, and no secondary phases were detected. Furthermore, a dense microstructure and small grain size lead to a high breakdown electric field strength (EB) of 430 kV/cm of the NBCSTO ceramic, which also displays the features of relaxor ferroelectrics. Importantly, a high Wrec⁓5.84 J/cm3 along with a medium η⁓80 % were simultaneously achieved in the NBCSTO ceramic, as well as good energy-storage stability. Moreover, the NBCSTO ceramic exhibits both a high PD and a fast discharging speed. All the above results indicate that the NBCSTO ceramic may be potential eco-friendly material for capacitor used in the pulsed power systems.

Neuromorphic synaptic applications of HfAlOx-based ferroelectric tunnel junction annealed at high temperatures to achieve high polarization

HfO2-based ferroelectric tunnel junctions (FTJs) are promising nonvolatile memory types for neural network applications because of their speed, low power, and excellent complementary metal-oxide semiconductor compatibility. Specifically, HfAlOx (HAO) has led to extensive research efforts owing to its outstanding ferroelectric performance. This is a result of the fact that the atomic radius of Al is smaller than that of Hf. In this study, we investigate the metal–ferroelectric–semiconductor device with an Al doping concentration of 2% that was annealed at 900 °C. A high-remnant polarization (Pr) value of 39.85 µC/cm2 and endurance were achieved by using the polarization switching positive-up-negative-down measurement method at this annealing condition. Our device shows long-term potentiation and depression properties, including high linearity and multiple conductance states for neuromorphic applications. Moreover, paired-pulse facilitation was implemented to mimic human synaptic functions. The construction of 16 states comprising four bits was achieved by employing reservoir computing with the FTJ device functioning as a physical reservoir. Finally, the results obtained from the experiment show promising outcomes for the ferroelectric memory characteristics and synaptic properties of the manufactured HAO device.