Next-generation Memory Research Articles

Atomic-Level Stoichiometry Control of Ferroelectric HfxZryOz Thin Films by Understanding Molecular-Level Chemical Physical Reactions.

HfO2-based thin films have garnered significant interest for integrating robust ferroelectricity into next-generation memory and logic chips, owing to their applicability with modern Si device technology. While numerous studies have focused on enhancing ferroelectric properties and understanding their fundamentals, the fabrication of ultrathin HfO2-based ferroelectric films has seldom been reported. This study presents the concept of atomic-level stoichiometry control of ferroelectric HfxZryOz films by examining the molecular-level interactions of precursor molecules in the atomic layer deposition (ALD) process through theoretical calculations. Atomic layer modulation (ALM) employs sequential precursor pulses, and the stoichiometries of HfxZryOz films are determined by the chemical and physical reactions predicted by theoretical simulations. The HfxZryOz ALM films demonstrate superior crystallinity and ferroelectricity compared to conventional HfxZryOz ALD films, with large polarization values reaching 2Pr = 48.8 μC/cm2 at a thickness of 4.5 nm. Because the ALM concept combines experimental and theoretical approaches, it can be applied to other applications that require multicomponent thin films with atomic-level stoichiometry control.

Gate-controllable two-dimensional transition metal dichalcogenides for spintronic memory

Rapid technological advancement has increased the demand for high-speed, low-power devices, particularly applied in artificial intelligence (AI) and the Internet of Things (IoT). Limitations of traditional memory devices underscore the urgency for high-performance, energy-efficient memory technologies. On the other hand, developing two-dimensional (2D) material-based devices is indispensable for next-generation memory and three-dimensional integration circuit (3D-IC) systems. Here, we propose a gate-controllable spin valve utilizing transition metal dichalcogenides (TMDs) to meet the urgent need. A high tunneling magnetoresistance (TMR) of over 4000% can be reached in reading with the help of the controlled gate. Moreover, under ungated conditions, a giant spin current density with an ultralow power consumption of 80 μW and a high spin-polarized ratio of 0.9 can be achieved, enabling high-speed and energy-efficient switching during writing. According to our design, the gate-controllable system can prevent undesired mixed reading and writing operations. Our results highlight TMDs as a promising material in spintronic memory devices.

Resistive switching behavior of quasi-2D CsPbBr3 memristors: Impact of ambient atmosphere on logic storage and computing integration with anti-crosstalk and reconfiguration features

Passive units integrating storage and computing with anti-crosstalk and multi-logic reconstruction are crucial for high computing power and high-density non-volatile storage. In this study, we report an anti-crosstalk and reconfigurable logic memory based on a single passive quasi-two-dimensional (2D) CsPbBr3 device. The effect of the ambient atmosphere (air and N2 environments) on the resistive behavior of the memristors is explored. In air, these devices exhibit negative differential resistance (NDR) effects and antipolar resistive switching behavior, while in N2, they display irreversible switching from low-resistance state to high-resistance state. Various active electrodes (Ag, Cu, Au, and C) were employed to investigate this phenomenon. It is proposed that in air, O ions interact with surface defects under high alternating voltage, retaining a significant quantity of Br− ions within the quasi-2D CsPbBr3, resulting in capacitive-like behavior. Conversely, in N2, surface defects capture Br− ions, leading to the absence of a hysteresis loop in the I-V characteristic. Under N2 operation, write-once-read-many (WORM) capability is achieved. Surprisingly, operating under air enables integrated non-volatile storage and computing, facilitating 12 reconfigurable logic operations in a passive 1R structure and suppressing sneak current in crosstalk setups. This study emphasizes the pivotal role of air in the resistive switching mechanism and provides novel insights for developing next-generation memories tailored for high-density integrated circuits and storage-computing integration.

Composition-Graded Nitride Ferroelectrics Based Multi-Level Non-Volatile Memory for Neuromorphic Computing.

Multi-level non-volatile ferroelectric memories are emerging as promising candidates for data storage and neuromorphic computing applications, due to the enhancement of storage density and the reduction of energy and space consumption. Traditional multi-level operations are achieved by utilizing intermediary polarization states, which exhibit an unpredictable ferroelectric domain switching nature, leading to unstable multi-level memory. In this study, a unique approach of composition-graded ferroelectric ScAlN to achieve tunable operating voltage in a wide range and attain precise control of domain switching and stable multi-level memory is proposed. This non-volatile memory supports multi-level storage up to 7-bit capacities, and exhibits enhanced performance compared to the uniform composition device, showing one order of magnitude higher ON/OFF ratio, 30% reduced working voltage, and up to 50% enhanced tuning window of operating voltage. Finally, the emulation of long-term plasticity and linear weight update akin to biological synapse with high uniformity and reliability are demonstrated. The proposed composition-grading architecture offers new opportunities for next-generation multi-level ferroelectric memories, paving the way for advanced hybrid integration in multifunctional computing systems.

Resistivity Engineering of Atomic Layer Deposited Tungsten Carbonitride Thin Films Via Carbon Concentration Control for Cross-Point Memory Electrodes Applications

As the demand for data storage and processing continues to rise exponentially, the development of phase change memory (PCM) has gained significant attention. In particular, three-dimensional (3D) vertical cross-point (VXP) array architecture is one of the most promising solutions for PCM fabrication, offering increased integration density and cost-effectiveness compared to the conventional planar memory structures, realized by atomic layer deposition (ALD) due to its excellent controllability and conformality.1) However, the implementation of a 3D VXP structure necessitates selectors, such as an ovonic threshold switch (OTS), to suppress sneak current from unselected cells. The switching behavior of the OTS selector depends heavily on electrode materials, constituting an essential part of the OTS device.2) Thus, detailed engineering of electrode material is required to obtain desirable properties for 3D VXP. Electrodes for 3D VXP require moderate resistivity because of the trade-off between thermal efficiency and power consumption. Moreover, the resistivity of film can be shifted by carbon incorporation. In this regard, we controlled the resistivity of the electrode with varying carbon concentration of the film utilizing ALD technique. In this study, we focus on the development of thermal ALD tungsten carbonitride electrodes for 3D VXP arrays. Tungsten nitride is mainly used as an electrode due to its high thermal stability and conductivity. We present a novel ALD process with intentional carbon control of tungsten nitride to change film properties, including resistivity, by adjusting process parameters. Through systematic control of ALD process parameters, we investigated the impact of carbon concentrations on film characteristics and subsequently analyzed how these variations influence the electrical properties of OTS devices. This research opens the possibility of tuning electrode characteristics in detail, ultimately enhancing the overall electrical performance of the next-generation cross-point memory devices.

Enhancing a-IGZO Thin-Film Transistors Performance Via Multi-Parameter Machine Learning

Driven by miniaturization in accordance with Moore's Law, memory devices like DRAM and NAND have achieved significant performance improvements. However, this relentless scaling has encountered fundamental physical limitations, hindering further miniaturization of traditional silicon (Si)-based transistors and restricting further performance gains. To confront this challenge, research is actively exploring new materials and architectures. Among these promising candidates, the Indium Gallium Zinc Oxide (IGZO) channel transistor has emerged as particularly attractive due to its advantages in low leakage current. Despite the advantages of IGZO for low-power consumption, achieving high field-effect mobility, crucial for fast operation speeds in memory devices, remains a significant challenge.To overcome this limitation, a novel machine learning (ML)-based approach is proposed for fabricating high-performance, ultra-thin IGZO thin-film transistors (TFTs) using sputtering process for the channel. This method optimizes the sputtering process, resulting in IGZO TFTs with outstanding multiple electrical properties simultaneously. The fabricated TFTs exhibit a high field-effect mobility of 33.2 cm²/V·s, a near-zero threshold voltage of -0.05 V, and a channel with a sub-10nm thickness. The performance of the fabricated TFTs is comparable to that of transistors produced by Atomic Layer Deposition (ALD), a technique renowned for its ability to create ultra-thin films with high quality. This achievement implies the potential of sputtering process to overcome the throughput challenges of ALD. Leveraging machine learning's strengths, the proposed method guides the optimization of the sputtering process, eliminating the need for traditional labor-intensive and trial-and-error methods. This approach has the potential to significantly accelerate the development of next-generation memory devices with unprecedented efficiency and speed.

Permanent Strain Engineering of Molybdenum Disulfide Using Laser-Driven Stressors for Energy-Efficient Resistive Switching Memory Devices.

Strain engineering provides an attractive approach to enhance device performance by modulating the intrinsic electrical properties of materials. This is especially applicable to 2D materials, which exhibit high sensitivity to mechanical stress. However, conventional methods, such as using polymer substrates, to apply strain have limitations in that the strain is temporary and global. Here, we introduce a novel approach to induce permanent localized strain by fabricating a stressor on SiO2/Si substrates using fiber laser irradiation, thereby enabling precise control of the surface topography. MoS2 is transferred onto this stressor, which results in the application of ~0.8% tensile strain. To assess the impact of the internal strain on the operation of ReRAM devices, the flat-MoS2-based and the strained-MoS2-based devices are compared. Both devices demonstrate forming-free, bipolar, and non-volatile switching characteristics. The strained devices exhibit a 30% reduction in the operating voltage, which can be attributed to bandgap narrowing and enhanced carrier mobility. Furthermore, the strained devices exhibit nearly a two-fold improvement in endurance, presumably because of the enhanced stability from lattice release effect. These results emphasize the potential of strain engineering for advancing the performance and durability of next-generation memory devices.

(Invited) 2-Dimensional Halide Perovskite Memristors for Data Storage and Neuromorphic Computing

Halide perovskites, fascinating memristive materials owing to mixed ionic-electronic conductivity, have been attracting great attention as nonvolatile data storage and artificial synapses recently. However, polycrystalline nature in thin film form and instability under ambient air hamper them to be implemented in demonstrating reliable electronic devices. We successfully fabricated vertically aligned 2D halide perovskite films (V-HPs) for active layers of ReRAM and artificial synapses, showing moisture stability. Unlike random-oriented HPs, which exhibit negligible current hysteresis, V-HPs with Ag top electrodes exhibited highly stable and reliable binary memory performance. We built a flexible crossbar array to verify data storage capability, achieving a high (~100 %) device yield, robust endurance (5 × 106 cycles), long retention (2 × 105 s), reliability to operate under bending conditions, and moisture stability over a year. V-HPs with Au top electrodes showed multilevel analog memristive characteristics, programmable potentiation and depression with distinguished multi-states, long-short-term plasticity, paired-pulse facilitation, and even spike-timing-dependent plasticity. Our findings provide material design strategy that can be extended to the development of new semiconductor materials for next-generation memory devices.

(Invited) Correlating Device Physics with Material Chemistry in Hafnia-Based Ferroelectric Memory Systems

The discovery of ferroelectricity in (Hf,Zr)O2 (HZO) thin films in 2011 [1] ignited renewed exploration into ferroelectric memory technologies, such as ferroelectric random-access-memory (FeRAM) and ferroelectric field-effect-transistor (FeFET), which offer promising avenues for next-generation memory solutions.[2-5] Despite the commercialization of FeRAM using traditional materials like Pb(Zr,Ti)O3 and SrBi2Ta2O9, its niche presence indicates a gap in mainstream adoption for high-density information storage.[3-5] Conversely, HfO2 and ZrO2, integrated into mainstream semiconductor devices like metal-oxide-semiconductor field-effect-transistor (MOSFET) and dynamic random-access-memory (DRAM), suggest compatibility with established fabrication processes, hinting at the potential of ferroelectric HZO for next-gen memory. Unlike electron-stored DRAM and Flash, ferroelectric memories store data based on material polarization, underlining the substantial impact of material properties on device performance. Thus, understanding the physics and chemistry of ferroelectric HZO is paramount for enhancing memory performance, given the intricate interplay of intrinsic and extrinsic factors such as thermodynamics, polymorphism, doping effects, and surface energy. [2,6-8]This presentation provides a comprehensive examination of hafnia-based ferroelectrics and their applications in semiconductor devices, underscoring the intrinsic link between device physics and material chemistry.[9] Specifically, the integration into next-gen memory devices like DRAM and Flash is explored. Managing trade-offs between remanent polarization (Pr) and endurance, crucial for demanding DRAM applications, requires reducing coercive field (Ec), which directly impacts operational voltage. Recent advancements in depositing metal-rich HZO film via sputtering show promise, with potential implications for FeRAM implementation through ALD. [10]Regarding flash operation, read disturbance poses a significant challenge to FeFET NAND functionality, necessitating optimal Pr and Ec ratios in ferroelectric materials. While achieving high Pr is a focus, excessive Pr can be detrimental to gate insulators, requiring a balance to avoid charge trapping and fatigue. Uniformly attaining suitable Pr and Ec values in hafnia-based ferroelectrics remains a considerable challenge without significant breakthroughs. Evaluation of FeFET performance reveals notable advancements in material chemistry control, enabling endurance up to 1010 cycles and write times as low as 300 ps, indicating a promising trajectory for FeFET technology.While substantial progress has been made in understanding material properties and exploring device applications in the first decade of ferroelectric HZO research, ongoing assessment and future directions are critical. Addressing device issues and material property challenges are urgent for practical applications in mainstream memory devices. Furthermore, concerns regarding circuitry and system integration in large-scale ferroelectric memory arrays necessitate continued research and development efforts. Despite these challenges, the benefits of ferroelectric materials and devices in semiconductor applications justify sustained exploration and innovation.[1] T. S. Böscke et al. Appl. Phys. Lett. 2011, 99 (10), 102903.[2] M. H. Park et al. Adv. Mater. 2015, 27 (11), 1811-1831.[3] U. Schroederet al. Nature Reviews Materials 2022, 7 (8), 653-669.[4] M. H. Park et al. MRS Commun. 2018, 8 (3), 795-808.[5] J. Y. Park, D.-H. Choe, D. H. Lee et al. Adv. Mater. 2023, 35 (43), 2204904.[6] M. H. Parket al. Nanoscale 2017, 9 (28), 9973-9986.[7] Y. Lee et al. Mater. Sci. Semicond. Process. 2023, 160, 107411.[8] J. Lee et al. Nano Converg 2023, 10 (1), 55.[9] H. Choi and Y. H. Cho et al. J. Phys. Chem. Lett. 2024, 15 (4), 983-997.[10] Y. Wang et al. Science 2023, 381 (6657), 558-563.

(Invited) Ultra-thin Oxide TFTs and Related Instabilities

Keywords: Amorphous oxide semiconductors, Ultra-thin oxide TFTs, NBTS, PBTSRecently, amorphous oxide semiconductors have attracted much attention for BEOL-compatible electronics such as next-generation memory applications (e.g. 2T0C). For practical use of oxide TFTs in BEOL-compatible electronics, ultra-thin channel thickness is essential. However, we have recently discovered that the well-known reliability issues such as negative bias temperature stress (NBTS) and positive bias temperature stress (PBTS) become more serious in ultra-thin oxide TFTs. In this respect, we investigated on how channel thickness relates with the instabilities in this study. As seen in Fig.1, PBTS instability becomes worse with the decrease in channel thickness. It is discovered that back-channel trap states are critical to PBTS instabilities, and such a back-channel effect appears more seriously when the channel thickness decreases. More details including experimental evidence and TCAD simulation results will be discussed at the conference. Figure 1. Comparison of positive bias temperature stress (PBTS) test results of IGZO TFTs with different channel thickness (7, 15, 20, 30, 40, 60 nm).

Hafnia-Based Ferroelectric Transistor with Poly-Si Gates for Gate-First Three-Dimensional NAND Structures.

Ferroelectric transistors based on hafnia-based ferroelectrics have emerged as promising candidates for next-generation memory devices. Additionally, hafnia-based ferroelectric transistors are suggested for three-dimensional (3D) memory devices, such as 3D ferroelectric NAND. This paper investigates the utilization of poly-Si as a gate material for hafnia-based ferroelectric transistors in 3D NAND structures. Conventional gate materials, such as TiN or W, are usually deposited in 3D NAND structures by using the gate-last process, which requires an additional gate replacement process. We demonstrate that poly-Si can be used as a gate material for hafnia-based ferroelectric transistors. We show that the 3D ferroelectric NAND based on the poly-Si gate can be fabricated by a simpler gate-first process without requiring a gate replacement process. Our findings underscore the potential of poly-Si as a gate material for ferroelectric transistors and 3D ferroelectric NAND.

Investigation of self-selective RRAM based on V/ITO structure with rapid thermal annealed ITO for synapse emulation

This paper focuses on the investigation of V/ITO (O2 Rapid Thermal Annealing)-based Self-Selective Resistive Random-Access Memory (RRAM) device. In this study, the natural oxidation of Vanadium top electrode and the rapid thermal annealing (RTA) process greatly simplified the device fabrication process. The VO2-based Selector, formed by the natural oxidation of the Vanadium electrode, effectively suppresses current and is directly integrated with the ITO layer, eliminating the need for additional serial Selector. The oxygen content of the ITO film is significantly increased by the RTA process, enabling the previously conductive ITO material to be used as the RRAM insulating layer without the need for additional deposition of insulating layer. This V/ITO (O2 RTA) structure not only exhibits highly uniform resistance distributions (σ/μ<2.8 %) and endurance stability (10000 cycles), but also effectively simulates synaptic plasticity, exhibiting both short-term and long-term memory behaviors. Notably, potentiation and depression characteristics are displayed by the device when continuous pulse voltage is applied. These advancements underscore the innovation and applicability of RTA-treated ITO films in next-generation memory technologies.

Exploring Fast Domain Wall Motion and DMI Realization in Compensated Ferrimagnetic Nanowires

Abstract Recent advancements in spintronics have spurred interest in current-induced domain wall motion (CIDWM) as a promising avenue for next-generation memory technologies. While previous research has predominantly focused on thin ferromagnetic films, recent attention has shifted towards ferrimagnetic materials due to their potential for magnetization compensation and efficient domain wall (DW) motion. In this study, we investigated the dynamics of DWs in compensated ferrimagnetic Pt/GdxFe1-x nanowires through experimental characterization and analysis. Our results reveal fast DW motion around the magnetic compensation point, indicating the influence of spin-orbit torque induced by current flow. We systematically explore the Dzyaloshinskii-Moriya interaction (DMI) field across different compositions of GdFe, observing elevated DMI field values near the compensation compositions. Additionally, we examine the impact of wire width and pulse duration on DW velocity, demonstrating higher velocities in narrower wires and shorter pulse durations. In the 1 μm wire, a DW velocity of around 3200 m/s was achieved by applying a 3 ns short pulse current. Our findings elucidate the intricate interplay between film composition, magnetic properties, wire width, pulse duration, and DW dynamics, providing valuable insights for the design and optimization of ferrimagnetic materials for future magnetic memory technologies.

A 32-Gb/s Single-Ended PAM-4 Transceiver With Asymmetric Termination and Equalization Techniques for Next-Generation Memory Interfaces

A 32-Gb/s Single-Ended PAM-4 Transceiver With Asymmetric Termination and Equalization Techniques for Next-Generation Memory Interfaces

Comparative Study of Current-Induced Torque in Cr/CoFeB/MgO and W/CoFeB/MgO.

Orbital torque (OT) in magnetic heterostructures has been actively discussed in terms of its actual existence and usefulness in comparison to the spin-orbit torque (SOT) that shows promise for next-generation magnetoresistive random access memories. The objectives of this study are 2-fold: (i) making an apples-to-apples comparison in two representative stacks where OT and SOT are expected to dominate and (ii) examining the potential emergence of OT in archetypal SOT stacks. Cr/CoFeB/MgO and W/CoFeB/MgO are chosen as the OT- and SOT-dominant systems, respectively. Systematic variations in each layer's thicknesses reveal that (i) Cr/CoFeB/MgO exhibits substantial torque comparable to or even exceeding that of the W/CoFeB/MgO stack when Cr and CoFeB layers are especially thick and (ii) the torque in W/CoFeB/MgO changes sign with increasing W and CoFeB thicknesses, suggesting a crossover of the dominant mechanism from SOT to OT. The findings clarify the opportunities and challenges of devices leveraging SOT and OT.

Single-molecule Magnets (SMM) spin channels connecting FeMn antiferromagnet and NiFe ferromagnetic electrodes of a tunnel junction

The integration of single-molecule magnets (SMMs) into magnetic tunnel junctions (MTJs) offers significant potential for advancing molecular spintronics, particularly for next-generation memory devices, quantum computing, and energy storage technologies such as solar cells. In this study, we present the first demonstration of SMM-induced spin-dependent properties in an antiferromagnet-based MTJ molecular spintronic device (MTJMSD). We engineered cross-junction-shaped devices comprising FeMn/AlOx/NiFe MTJs. The AlOx barrier thickness where the exposed junction edges meet was comparable to the SMM length, facilitating the incorporation of SMM molecules as spin channels for spin-dependent transport. The SMM channels enabled long-range magnetic moment ordering around molecular junctions, which were precisely engineered via fabrication processes. The SMM, composed of a [Mn6(μ3-O)2(H2N-sao)6(6-atha)2(EtOH)6] (H2N-saoH = salicylamidoxime, 6-atha = 6-acetylthiohexanoate) complex, featured thioester groups at the ends that upon hydrolysis they form bonds with the magnetic electrodes. SMM-treated junctions demonstrated a significant current enhancement, reaching up to 7 μA at an input voltage of 60 mV. Furthermore, SMM-doped junctions exhibited current stabilization in the μA range at lower temperatures, whereas the bare electrodes showed current suppression to the picoampere range. Magnetization measurements conducted at 55 K and 300 K on pillar-shaped devices revealed a reduction in magnetic moment at low temperatures. Additionally, Kelvin probe atomic force microscopy (KPAFM) measurements confirmed that SMM integration transformed the electronic properties over long ranges.These findings are attributed to the spin channels formed between magnetic metal electrodes, which enhance spin polarization at each magnetic electrode. Our research highlights the potential of using antiferromagnetic materials, characterized by minimal stray fields and zero net magnetization, to transform MTJMSD devices.

Crystal Chemistry and Design Principles of Altermagnets.

Altermagnetism was very recently identified as a new type of magnetic phase beyond the conventional dichotomy of ferromagnetism (FM) and antiferromagnetism (AFM). Its globally compensated magnetization and directional spin polarization promise new properties such as spin-polarized conductivity, spin-transfer torque, anomalous Hall effect, tunneling, and giant magnetoresistance that are highly useful for the next-generation memory devices, magnetic detectors, and energy conversion. Though this area has been historically led by the thin-film community, the identification of altermagnetism ultimately relies on precise magnetic structure determination, which can be most efficiently done in bulk materials. Our review, written from a materials chemistry perspective, intends to encourage materials and solid-state chemists to make contributions to this emerging topic through new materials discovery by leveraging neutron diffraction to determine the magnetic structures as well as bulk crystal growth for exploring exotic properties. We first review the symmetric classification for the identification of altermagnets with a summary of chemical principles and design rules, followed by a discussion of the unique physical properties in relation to crystal and magnetic structural symmetry. Several major families of compounds in which altermagnets have been identified are then reviewed. We conclude by giving an outlook for future directions.

Enhancing Charge Trapping Performance of Hafnia Thin Films Using Sequential Plasma Atomic Layer Deposition.

We aimed to fabricate reliable memory devices using HfO2, which is gaining attention as a charge-trapping layer material for next-generation NAND flash memory. To this end, a new atomic layer deposition process using sequential remote plasma (RP) and direct plasma (DP) was designed to create charge-trapping memory devices. Subsequently, the operational characteristics of the devices were analyzed based on the thickness ratio of thin films deposited using the sequential RP and DP processes. As the thickness of the initially RP-deposited thin film increased, the memory window and retention also increased, while the interface defect density and leakage current decreased. When the thickness of the RP-deposited thin film was 7 nm, a maximum memory window of 10.1 V was achieved at an operating voltage of ±10 V, and the interface trap density (Dit) reached a minimum value of 1.0 × 1012 eV-1cm-2. Once the RP-deposited thin film reaches a certain thickness, the ion bombardment effect from DP on the substrate is expected to decrease, improving the Si/SiO2/HfO2 interface and thereby enhancing device endurance and reliability. This study confirmed that the proposed sequential RP and DP deposition processes could resolve issues related to unstable interface layers, improve device performance, and enhance process throughput.

Observation of Néel-type magnetic skyrmion in a layered non-centrosymmetric itinerant ferromagnet CrTe1.38

Magnetic skyrmions are nanoscale vortex-like magnetization textures that hold great promise for next-generation memory and spintronic devices. While extensive research has focused on discovering such localized spin textures in bulk magnets and multilayers with heavy metals, there is a growing interest in finding them in two-dimensional (2D) magnetic materials. In this research work, we report two distinct phases of the 2D CrxTey family: non-centrosymmetric CrTe1.38 and centrosymmetric CrTe0.96, with a Curie temperature of around 200 and 300 K, respectively. Detailed magnetic study indicates a prominent out-of-plane magnetic anisotropy in CrTe1.38. In contrast, CrTe0.96 exhibits a weak uniaxial magnetic anisotropy. Lorentz transmission electron microscopy shows that the spontaneous ferromagnetic ground state of CrTe1.38 consists of Néel skyrmions, whereas CrTe0.96 exhibits Bloch domain walls, consistent with their crystalline symmetries. This research expands the quasi-2D CrxTey family and opens up new avenues for exploring non-trivial spin structures and their potential applications in spintronic devices.

Radiation Hardened Read-Stability and Speed Enhanced SRAM for Space Applications

With the advancement of CMOS technology, the susceptibility of SRAM to single node upset (SNU), double node upset (DNU), and multiple node upset (MNU) induced by radiation has increased. To address this issue, various cutting-edge solutions, such as radiation hardened sextuple cross coupled (RHSCC)-16T and DNU-completely-tolerant memory (DNUCTM) cells, have been proposed. While the RHSCC-16T cell is robust against SNU, it may be vulnerable to DNU. The DNUCTM cell is resistant to both SNU and DNU, but it remains susceptible to MNU. In this paper, we propose a radiation hardened read-stability and speed enhanced (RHRSE)-20T SRAM, which is immune to all potential cases of SNU, DNU, and MNU. Additionally, the proposed design demonstrates improvements in read and write delays compared to conventional SRAM designs. Experimental results confirm that the RHRSE-20T SRAM maintains stability under various charge levels for SEU, DNU, and MNU. The proposed integrated circuit is implemented in a 90-nm CMOS process and operates on a 1 V supply voltage, offering significant advantages for next-generation radiation-hardened memory applications.