Search Results (141)

Hafnium−zirconium oxide (HZO)−based ferroelectric field−effect transistors (FeFETs) are expected to become core devices for new embedded memory and compute−in−memory systems. However, existing simulations rely on finite−element−based TCAD tools, which are computationally intensive and time−consuming, and they struggle to account for the dynamic flipping of ferroelectric domains. This paper utilizes a time−domain simulation framework based on the nucleation−limited switching (NLS) model coupled with the surface potential of a MOSFET, enabling a self−consistent solution for polarization and electrical characteristics; a Monte Carlo method is employed to simulate device variability, and Shmoo plots are used to identify optimal programming and erasure process windows; an integrated solution is proposed for 22 nm FDSOI devices, addressing geometric scaling, modification of the Landau–Khalatnikov (L−K) dynamic model for ultrathin ferroelectric layers, and suppression of short−channel effects. Model validation is limited to selected operating metrics, and predictive accuracy outside the calibrated cases requires additional independent datasets. This method enables end−to−end simulation of FeFETs, from material polarization and device electrical characteristics to performance optimization, thereby providing model−based analytical and design support for the development of advanced, ultra−low−power FeFETs. Full article

Ferroelectric (FE) diodes configured in the metal–ferroelectric–metal (MIFM) structure are promising candidates for non-volatile memory. While recent studies emphasized bulk FE properties, interfacial characteristics have not been carefully considered. In this work, we investigate the HfO₂/Al_0.8Sc_0.2N interface by examining its impact on switching and rectifying characteristics in MIFM FE diodes with variable HfO₂ thicknesses (2/4/6 nm). Electrical characterization reveal that the increased HfO₂ thickness raises the coercive field (E_C) due to enhanced electrostatic effects and progressive interfacial oxidation from Sc-N to Sc-O bonds. This resulting oxygen substitutional defect (O_N) which may contribute to domain-wall pinning and reduced rectifying efficiency. Cycling tests clarify operating regime-dependent phenomena, including O_N redistribution-induced wake-up and eventual breakdown. Moreover, enhanced retention is observed after pre-cycling, originating from the stabilization of the interfacial defects rather than bulk properties. These findings underscore that E_C and device reliability are likely influenced by interfacial engineering, which is critical for the reliable operation of AlScN-based FE diodes. Full article

Van der Waals (vdW) multiferroic tunnel junctions (MFTJs) based on two-dimensional layered materials have emerged as a promising platform for next-generation non-volatile memory devices. In this work, we propose and theoretically investigate a high-performance all-vdW MFTJ consisting of a sliding ferroelectric bilayer GeC barrier sandwiched between asymmetric ferromagnetic metallic electrodes, Fe₃GaTe₂ and Fe₃GeTe₂. Using first-principles calculations combined with the non-equilibrium Green’s function (NEGF) method, we demonstrate that the bilayer GeC possesses robust vertical ferroelectricity switchable by interlayer sliding. By incorporating monolayer graphene as protective layers to mitigate metal-induced gap states, the device preserves the intrinsic ferroelectric polarization of the barrier. Our results reveal that four distinct non-volatile resistance states can be realized by independently manipulating the ferroelectric polarization and magnetization configurations. Remarkably, the device exhibits a giant Tunneling Magnetoresistance (TMR) ratio of up to 750.95% and a large Tunneling Electroresistance (TER) ratio of 322.97%. Furthermore, we observe perfect spin-filtering efficiency and a significant negative differential resistance (NDR) effect under finite bias voltage. These findings suggest that the Fe₃GaTe₂/graphene/bilayer-GeC/graphene/Fe₃GeTe₂ heterostructure is a compelling candidate for multifunctional spintronic applications in the post-Moore era. Full article

This paper presents the design of a batteryless near-field communication (NFC) multi-sensor node with an integrated adaptive power-management system for sensing applications. The work focuses on harvesting energy from a 13.56 MHz NFC field to power an ultra-low power sensing platform. The design consists of the TI RF430FRL152H, an integrated NFC transponder with an embedded MSP430 microcontroller core and ferroelectric random-access memory (FRAM) non-volatile memory. The system combines an ISO/IEC 15693 NFC front end, a tuned loop antenna for optimized power harvesting, and multiple analog and digital sensor interfaces, and a firmware architecture for intermittent harvested energy operation. The aforementioned design performs on-demand data acquisition, logs measurements in the FRAM, and communicates the measured results through an ISO15693 compliant NFC link while powered entirely by the reader’s radio-frequency (RF) field. Since NFC provides only limited harvested power, efficient energy management is critical. The proposed scheme continuously monitors the storage capacitor voltage and activates each sensor only when sufficient energy is available. After every measurement, the system reassesses the stored charge before triggering the next acquisition, ensuring stable multi-sensor operation. A BMP390 temperature and pressure sensor and the on-chip temperature sensor demonstrate the platform’s capability. Experimental results show that the system harvests 1.064 mW (1.85 V, 560 µA), achieves a wireless operating range of up to 40 mm, and delivers a response time of 800 ms, demonstrating its suitability for low-power temperature and pressure sensing applications. Full article

Hafnium oxide thin films have been extensively investigated for high-speed and low-power memory applications. Herein, we investigated the influence of oxygen vacancies and external stress on the ferroelectric characteristics of Al-doped HfO₂ (HfAlO). Compared with HfAlO with 14% oxygen vacancies, films with 21% oxygen vacancies could lower the polarization switching barrier and increase the fraction of the ferroelectric phase. Furthermore, significant external stress promotes ferroelectric phase formation, thereby enhancing ferroelectric characteristics. The remanent polarization achieved with W electrodes (2Pr = 38 µC/cm²) is about 18 times that of Au electrodes, owing to the lower thermal expansion coefficient of W electrodes. Density functional theory calculations and finite element analysis provide theoretical insights corroborating the experimental results, helping to pave the way for developing hafnium-based materials for next-generation in-memory computing applications. Full article

Interlayer-sliding ferroelectricity in van der Waals bilayers enables ultralow-power switching, but practical devices are often limited by contact/interface scattering and weak coupling between polarization and transport. We propose homophase lateral architectures based on bilayer Janus MoSSe: a 1T/2H/1T ferroelectric tunnel homojunction and an H-phase lateral p–i–n photodetector (artificially doped electrode). Metallic 1T electrodes largely eliminate contact barriers and maximize polarization-driven tunneling modulation. Using non-equilibrium Green’s function–density functional theory (Perdew–Burke–Ernzerhof approximation, without explicit spin–orbit coupling), we find that AB to BA sliding reduces the current from the nA range to the pA range, with the minimum current of|I_OFF|_min = 2.83 pA, yielding giant tunneling electroresistance up to 5.3 × 10⁴%. Projected local density of states reveals a non-rigid long-range potential redistribution that reshapes the tunneling barrier and opens high-transmission channels. In the p–i–n photodetector, the response is strongly anisotropic and stacking-dependent: AB reaches photocurrent density J_ph ≈ 7.2 µA·mm⁻² at 2.6 eV for in-plane light versus ≈ 2.9 µA·mm⁻² at 3.5 eV for out-of-plane, and exceeds BA by 1.5–1.8 times due to density of states advantages and Mo-d orbital selection rules. Bilayer Janus MoSSe therefore provides a reconfigurable platform for high-contrast memory and polarization-sensitive photodetection. Full article

As emerging nonvolatile memory devices, ferroelectric field-effect transistors (FeFETs) have attracted significant attention for memory applications. However, due to the stochastic nature of fabrication processes and material properties, FeFETs exhibit pronounced device-to-device (DTD) variations, leading to threshold voltage dispersion and inconsistency in memory window (MW), which severely constrain array-level performance and reliability. In this study, a compact model-based variability analysis methodology for FeFETs has been proposed. Specifically, the Preisach ferroelectric (FE) hysteresis model was combined with the MIT Virtual Source (MVS) physical compact model to establish a macro-model for FeFETs, and statistical simulations were performed to evaluate device-level variations. Using the proposed framework, how fluctuations in two key FE parameters, film thickness (t_FE) and coercive field (E_C), affect FeFET transfer characteristics, threshold voltage (V_TH), and MW was systematically investigated. Monte Carlo (MC) simulations were further conducted to quantify the distribution width and statistical features of V_TH under different variability scenarios. The results indicate that random fluctuations in process-related parameters broaden the FeFET I_d-V_g characteristics, induce shifts in high/low threshold voltages, and cause MW variations. Moreover, when t_FE and E_C fluctuate simultaneously, the dispersions of V_TH and MW become significantly larger than those induced by a single-parameter fluctuation. The proposed compact-modeling framework and variability analysis approach enables the efficient evaluation of parameter tolerance and performance margin in FeFET arrays, providing guidance for storage-array design. Full article

Emerging non-volatile memories based on ferroelectric materials are currently under development to be integrated in the back-end-of-line of advanced complementary metal-oxide-semiconductor (CMOS) nodes. A life cycle assessment (LCA) over 16 impact categories has been carried out to compare planar (2D) and vertical (3D) integration strategies for the manufacturing of Hf_0.5Zr_0.5O₂-based ferroelectric capacitors on a 22 nm CMOS technology node. The LCA demonstrates that the 3D approach allows us to reduce the environmental impacts by up to 20% over several impact categories. The device isolation by a single chemical–mechanical polishing (CMP) step instead of the standard photolithography and plasma etching processes proved to be the main source of reduction on the overall environmental footprint. Full article

The von Neumann architecture faces severe bottlenecks in energy efficiency. Computing-in-Memory (CiM) addresses this by performing computations within memory arrays, yet analog CiM solutions suffer from precision loss and high overhead from analog-to-digital converters and digital-to-analog converters (ADCs/DACs). This paper proposes a novel ADC-free CiM architecture based on Ferroelectric Field-Effect Transistors (FeFETs). Logic circuits (NOR, NAND, XNOR) that store weight vectors within FeFETs were designed. Compared with analog CiM circuits, the FeFETs-CiM circuits proposed in this paper can reduce power consumption by 901.1 times and latency by 272.7 times. Furthermore, the design of 3-bit FeFETs-CiM gates was extended, demonstrating flexible configurability for scalable edge computing applications. Finally, an application specific FeFETs-CiM subtractor for k-nearest neighbor (kNN) distance calculation was designed, which energy consumption is as low as 85.02 fJ/OP and latency is as low as 0.56 ns under 500 MHz operation frequency. The calculation robustness of the FeFETs-CiM kNN distance calculator was ensured by simulating under different process corners and temperatures. The performance improvements owing to the proposed FeFETs-CiM CMOS circuits were evaluated by taking the kNN algorithm as an example, which can ensure the data access reduction by more than 300 times compared to von Neumann architecture. Full article

Due to the Von Neumann bottleneck of traditional CMOS computing, there is an urgent need to develop in-memory logic devices with low power consumption. In this work, we demonstrate ferroelectric diode devices based on the TiN/Hf_0.5Zr_0.5O₂/HfO₂/TiN structure, implementing 16 Boolean logic operations through single-step or multi-step (2–3 steps) cascade and achieving attojoule-level one-bit full-adder computation. The TiN/Hf_0.5Zr_0.5O₂/HfO₂/TiN ferroelectric diode exhibits non-destructive readout and bidirectional rectification characteristics, with the conduction mechanism following Schottky emission behavior in the on-state. Based on its bidirectional rectification characteristics, we designed and simulated the circuit scheme of 16 Boolean logic and one-bit full-adder through cascaded operations. Both the input and output logic values are represented in the form of resistance, without the need for additional form conversion circuits. The state writing is performed by pulse-controlled polarization flipping, and the state reading is non-destructive. The logic circuits in this work demonstrate superior performance with ultralow computing power consumption in simulation. This breakthrough establishes a foundation for developing energy-efficient and scalable in-memory computing systems. Full article

The phase transitions and switching dynamics of topological polar textures in hafnium oxide (HfO₂)-based cylindrical-shell ferroelectrics are studied using a three-dimensional (3D) phase field model based on the self-consistent solution of the time-dependent Ginzburg–Landau model and Poisson equation. The comprehensive interplays of bulk free energy, gradient energy, depolarization energy, and elastic energy are taken into account. When a cylindrical ferroelectric device is biased under the in-plane radial electric field, there is a size-controlled phase transition between the ferroelectric (FE), antiferroelectric (AFE), and paraelectric (PE) phases, depending on ferroelectric film thickness and cylindrical shell radius. For in-plane polarization textures at the equilibriums, the FE phase has a Néel-like texture with a center-type four-quad domain, the AFE phase has a monodomain texture, and the PE phase has a Bloch-like texture with a vortex four-quad domain. These polarization domain textures are resultant from energy competition and topologically protected by the geometrical confinement. The polarization dynamics from polar states towards equilibriums are analyzed considering the separated contributions of x- and y-components of polarizations that are driven by x-y in-plane electric fields. The emergent topological domains and phase transitions provide guidelines for geometrical engineering of a novel nano-structured ferroelectric device that is different from the planar one, offering new possibilities for multi-functional high-density ferroelectric memory. Full article

Aluminum scandium nitride (Al_1−xSc_xN) is a promising ferroelectric material for non-volatile random-access memory devices and electromechanical sensors. However, adverse effects on polarization from electrical leakage are a significant concern for this material. We observed that the electrical conductivity of Al_1−xSc_xN thin films grown on epitaxial TiN(111) buffered Si(111) follows an Arrhenius-type behavior versus the growth temperature, suggesting that point defect incorporation during growth influences the electronic properties of the film. Photoluminescence intensity shows an inverse correlation with growth temperature, which is consistent with increased non-radiative recombination from point defects. Further characterization using secondary ion mass spectrometry in a focused ion beam/scanning electron microscope shows a correlation between trace Ti concentrations in Al_1−xSc_xN films and the growth temperature, further suggesting that extrinsic dopants or alloying components potentially contribute to the point defect chemistry to influence electrical transport. Investigation of the enthalpy of formation of nitrogen vacancies in Al_1−xSc_xN using density functional theory yields values that are in line with electrical conductivity measurements. Additionally, the dependence of nitrogen-vacancy formation energy on proximity to Sc atoms suggests that variations in the local structure may contribute to the occurrence of point defects, which, in turn, can impact electrical leakage. Furthermore, we have demonstrated ferroelectric behavior through electrical measurements and piezoresponse force microscopy after dc bias poling of films in spite of electrical conductivity spanning several orders of magnitude. Although electrical leakage remains a challenge in Al_1−xSc_xN, the material holds potential due to tunable electrical conductivity as a semiconducting ferroelectric material. Full article

Ferroelectricity in hafnium oxide (HfO₂)-based thin films has emerged as a scalable pathway toward CMOS-compatible non-volatile memories and logic devices. This study examines how dopant chemistry and film thickness influence the stabilization of the ferroelectric phase in ALD-grown HfO₂ thin films doped with Zr, Al, and Y. Structural, morphological, and electrical characterizations were carried out using AFM, GIXRD, P–E, in-plane I/W–E, and C–V measurements on films with thicknesses of 7 nm and 100 nm. AFM revealed atomically smooth and dense surfaces (R_q < 0.5 nm), while GIXRD confirmed the stabilization of the orthorhombic Pca2₁ phase in doped 7 nm films and its relaxation toward the monoclinic phase at 100 nm. The 7 nm HfZrO and HfYO films exhibited robust ferroelectric hysteresis with remanent polarization values up to 60 μC·cm⁻², whereas HfAlO showed a narrower but still distinct switching response. In-plane I/W–E characteristics indicated a combination of Poole–Frenkel and injection-limited conduction, consistent with defect-assisted polarization reversal and asymmetric contact barriers. At 100 nm, all films showed reduced polarization and partially dielectric behavior, as corroborated by the C–V data. These results demonstrate that nanoscale confinement, dopant-induced strain, and oxygen vacancy related defect chemistry collectively stabilize the orthorhombic ferroelectric phase, with Zr doping providing the most favorable balance between polarization strength and leakage control. Full article

The conventional static imprint effect in Hf_xZr_1−xO₂ (HZO) ferroelectric (FE) devices, which degrades data retention, is generally characterized by a shift in the hysteresis loop along the electric field axis. Unlike the static imprint effect, the dynamic imprint effect emerges under dynamic electric fields or actual operating conditions, making the FE film exceptionally sensitive to switching pulse parameters and domain history. In HZO anti-ferroelectric (AFE) devices, this dynamic imprint effect alters the coercive field distribution associated with domain switching and poses a significant challenge to long-term stable device operation. This study systematically investigates the dynamic imprint effect and its recovery process using a comprehensive integration of first-order reversal curve (FORC) analysis, transient current-voltage (I-V), and polarization-voltage (P-V) characterization. By analyzing localized imprint behavior under sub-cycling conditions, mechanisms and recovery pathways of imprint in AFE devices are proposed. Finally, possible physics-based mechanisms describing imprint behaviors and recovery behaviors are discussed, providing insights for optimizing AFE memory technology performance and reliability. Full article

Ba_0.6Sr_0.4TiO₃ (BST) thin films were deposited on ITO substrates via rf magnetron sputtering, followed by structural and morphological characterization using XRD and FE-SEM. Metal–insulator–metal (MIM) RRAM devices were fabricated by depositing Al top electrodes, and their electrical properties were examined through I–V measurements. The optimized BST films deposited at 40% oxygen concentration exhibited stable resistive switching, with an operating voltage of 3 V, an on/off ratio of 1, and a leakage current of 10⁻⁸ A. After rapid thermal annealing at 500 °C, the on/off ratio improved to 2 but leakage increased to 10⁻³ A. Incorporating an electron transport layer (ETL) effectively suppressed the leakage current to 10⁻⁵ A while maintaining the on/off ratio at 2. Moreover, a transition from bipolar to unipolar switching was observed at higher oxygen concentration (60%). These results highlight the role of ETLs in reducing leakage and stabilizing switching characteristics, providing guidance for the development of transparent, low-power, and high-reliability BST-based RRAM devices. This study aims to investigate the role of Ba_0.6Sr_0.4TiO₃ (BST) ferroelectric oxide as a functional switching layer in resistive random-access memory (RRAM) and to evaluate how interface engineering using an electron transport layer (ETL) can improve resistive switching stability, leakage suppression, and device reliability. Full article