Performance Of Memory Devices Research Articles

Enhanced performance of self-selective RRAM devices in V/TaOx/Pt structure

Abstract The performance of resistive random-access memory devices with vanadium as the top electrode and different TaOx insulating layer is investigated in this paper. The results indicate that the VO2 oxide layer generated by the oxidation of the vanadium electrode can serve as inherent selector, without the need for additional series selectors required in conventional methods. A large amount of oxygen vacancy migration was limited in the double insulating layers, enabling the device to achieve stable Self-Selective resistive random-access memory performance. This indicated that the advantage of the double insulation layers lay in manipulating the migration of oxygenions and vacancies. Endurance tests showed no degradation over 103 cycles, and the device maintained stability after 20,000 pulse applications. The subthreshold swing of the selector was less than 42 mV/dec, and the switching time was less than 2 μs. This research presents a promising advancement in resistive random-access memory technology with potential for high-density memory integration and reliable performance.

Aromaticity‐Dependent Memristive Switching

AbstractIn recent years, memristors have drawn attention as non‐volatile memory devices for advanced computing engineering. The features of memristors, such as hysteresis, high resistance state to low resistance state ratio, retention time, etc., are determined by the material, structure of the device, the switching mechanism, and the kinetics resulting from the characteristics of the materials. Here, a resistive switching is proposed based on the aromaticity change of the material. A device has been built based on tetracyclone that undergoes the transition from an antiaromatic to an aromatic state upon applied potential. This phenomenon results in the presence of two distinguishable, and more importantly, stable resistive states of the memristor. On the basis of theoretical and experimental investigation, it is demonstrated that the working principle of the device depends on the redox change of the molecules. This study provides the foundation for a new kind of memristive switching mechanism: the formation of virtual conductivity paths. They can be a key to improving the performance of semiconductor memory devices in crucial factors such as stability, reversibility, and nonvolatility because these paths are related to electron delocalization and do not involve any significant structural changes in the device (e.g., diffusion).

Engineering of ZrO2-based RRAM devices for low power in-memory computing

This work evaluates the impact of applying hydrogen plasma (H-plasma) either after the deposition of the ZrO2 layer or as an intermediate step during the deposition on the performance of resistive random-access memory devices. Devices treated with H-plasma exhibited lower power consumption during the forming process and a higher Ron/Roff ratio over 50 cycles of SET and RESET pulses compared to untreated devices. The position of the plasma treatment significantly influenced the device's performance. We measured the leakage current, which correlates well with the forming process. Devices with higher leakage current required less power during the forming process. It was observed that a thicker capping layer following plasma insertion reduced forming power and improved the conductance quantization for multilevel cell characteristics.

Convolutional neural network for high-performance reservoir computing using dynamic memristors

In the rapidly advancing field of neuromorphic computing, W/ZnO/TiN resistive random-access memory (RRAM) devices have emerged as a next-generation computational building block. Our findings reveal the significant role played by the thickness of the ZnO layer in determining the electrical properties essential for data storage and neuromorphic applications. The short-term memory (STM) capabilities, which are critical for processing temporal information, are closely examined alongside their potential to simulate biological synaptic functions through multilevel conductance states and synaptic behaviors such as paired-pulse facilitation. Integrating these devices into reservoir computing systems enhances pattern recognition and accelerates learning, which demonstrates their utility in sequential data processing. In addition, conductance modulation via pulse width adjustment is a novel strategy to optimize memory device performance. By showcasing the effectiveness of W/ZnO/TiN devices in neuromorphic computing through high-accuracy image recognition tasks, our study highlights their foundational role in advancing neuromorphic computing technologies. The adaptability, learning capabilities, and efficiency of these devices underscore their potential for developing hardware-based neuromorphic systems that are capable of complex data processing.

Tailoring magnetism in chromium-doped zinc cobalt ferrite nanostructure for advanced spintronic memory devices

Soft magnetic ferrites serve as a crucial component in a wide array of sensing and actuating applications across various industries, including consumer electronics, automotive systems, spintronics, and more. These materials also find utility in spintronics, particularly for next-generation magnetic random-access memory (MRAM) due to their excellent inductive properties, which enhance the performance and scalability of spintronic memory devices. This study focuses on fine-tuning soft magnetic ferrites for inductive applications by doping them with Cr ions. By utilizing advanced experimental techniques such as the vibrating sample magnetometer (VSM) for bulk magnetometry and X-ray magnetic circular dichroism (XMCD) alongside X-ray absorption spectroscopy for atomic studies, the research aims to investigate the structural, electronic, and magnetic properties of the nanoferrites. Addition of doping in the soft ferrites observes reduction in the general magnetic parameters, with the only exception being coercivity, which decreases from 381 Oe to 275 Oe as the doping concentration increases from x = 0 to x = 0.02, and then increases to 350 Oe at x = 0.03. Through such precise tuning of the nanoparticles, this study aims to investigate the controllable soft magnetic properties of the nanoferrites, thereby paving the way for fast access times, non-volatility, and low energy consumption, presenting a compelling alternative to conventional memory technologies.

Vortex Domain Wall Thermal Pinning and Depinning in a Constricted Magnetic Nanowire for Storage Memory Nanodevices.

In this study, we investigate the thermal pinning and depinning behaviors of vortex domain walls (VDWs) in constricted magnetic nanowires, with a focus on potential applications in storage memory nanodevices. Using micromagnetic simulations and spin transfer torque, we examine the impacts of device temperature on VDW transformation into a transverse domain wall (TDW), mobility, and thermal strength pinning at the constricted area. We explore how thermal fluctuations influence the stability and mobility of domain walls within stepped nanowires. The thermal structural stability of VDWs and their pinning were investigated considering the effects of the stepped area depth (d) and its length (λ). Our findings indicate that the thermal stability of VDWs in magnetic stepped nanowires increases with decreasing the depth of the stepped area (d) and increasing nanowire thickness (th). For th ≥ 50 nm, the stability is maintained at temperatures ≥ 1200 K. In the stepped area, VDW thermal pinning strength increases with increasing d and decreasing λ. For values of d ≥ 100 nm, VDWs depin from the stepped area at temperatures ≥ 1000 K. Our results reveal that thermal effects significantly influence the pinning strength at constricted sites, impacting the overall performance and reliability of magnetic memory devices. These insights are crucial for optimizing the design and functionality of next-generation nanodevices. The stepped design offers numerous advantages, including simple fabrication using a single electron beam lithography exposure step on the resist. Additionally, adjusting λ and d allows for precise control over the pinning strength by modifying the dimensions of the stepped areas.

Сегнетоэлектрические материалы в современных вычислениях

Background: Ferroelectric materials, known for their spontaneous electric polarization, are reshaping the landscape of modern computing. These materials have unique qualities, such as non-volatility, high-speed operation, and energy efficiency, which are critical for advancing modern computer technology. Objective: This study intends to investigate integrating ferroelectric materials into current computer systems, emphasizing to improve memory devices and processors and solve the accompanying technological obstacles and possibilities. Methods: A thorough analysis of existing literature and experimental data was carried out to determine the capabilities and limitations of ferroelectric materials in computing applications. Key performance indicators examined include polarization retention, energy consumption, scalability, and integration with existing semiconductor technology. Results: The results show that ferroelectric materials considerably increase memory device performance and efficiency by allowing quicker write/read operations and lowering power use. However, concerns such as material deterioration, data retention, and integration complexity with silicon-based technology remain. Conclusion: Ferroelectric materials provide exciting prospects for the next generation of computer technology. While they provide significant gains in memory and processing power, addressing the technological obstacles is critical to their effective adoption into mainstream computer applications. Further research and development are needed to solve these issues and fully realize the promise of ferroelectric materials in improving computer performance.

An ab-initio investigation of physical characteristics of GdSc1-xTMxO3(TM=Ti; x=0.25, 0.5, 0.75) for photo influenced (NIR)memory storage and allied devices

In the present study, we have computed the structural, electronic, and optical characteristics of pristine GdScO3 and GdSc1-xTMxO3 (TM = Ti; x = 0.25, 0.5, 0.75) for improved performance of Resistive Random Access Memory (RRAM) devices. All calculations have been performed using the Tran Balha-modified Becke Johnson (TB-mBJ) approximation within the framework of the WEIN2K simulation package. Herein, the effect of Ti-dopant (transition metal, i.e., TM) with varying concentrations has been observed, especially in tuning the energy band gap. The structural analysis of composites reveals structural stability and a significant reduction in bulk modulus with increasing dopant concentration, leading to enhanced electrical conductivity. The band structure analysis reveals that the band gap tends to decrease with increasing concentrations of Ti-dopant.As regards total density of states (TDOS), it has been found that with increasing concentrations of Ti, dopant extra states appear in the conduction band. This is the reason behind the formation of the conducting filaments (CF) within the active layer of RRAM devices. The partial density of states (PDOS) elaborates that for all studied composites, the formation of the conduction band (C.B.) and valence band (V.B.) is a consequence of the hybridization of Sc-3d, Gd-5d, and Ti-4d states, along with the minute contribution of O-2p states. Optical characteristics disclose the photoresponse of all studied composites, wherein GdSc0.25Ti0.75O3 exhibits wide range absorption, henceforth making it a making it a more suitable candidate for photoinfluencing, especially in near infrared (NIR) RRAM devices.

Mathematical analysis of spin transport in topological insulators to optimize memory devices performance using numerical simulations

Understanding spin transport in topological insulators (TIs) is crucial for the development of spin-based technologies, such as magnetic memory, sensors, and quantum bits. To optimize memory device performance, we developed a comprehensive mathematical model that describes the evolution of spin density, as a function of space and time, taking into account spin-momentum locking, spin-orbit coupling, spin dynamics, and diffusive transport processes (including phonon and impurity scattering). Using numerical simulations (finite element method and Backward Euler Method) implemented in Python, we analyzed the spin transport in TIs. Our study demonstrated a critical dependence of spin transport efficiency on device length, with a maximum efficiency of 75% at a length of 8 micrometers. Beyond a critical length of 10 micrometers, efficiency recovered, reaching 80% at 14 micrometers. We observed oscillatory behavior in spin polarization, with amplitude modulation indicating constructive and destructive interference patterns. The inclusion of spin-orbit coupling and Dirac terms in our model revealed a non-uniform spin polarization distribution, with a 30% increase in polarization near the center. Defects and boundaries significantly impacted spin transport, reducing polarization by 40% near the defect region. Through optimization, we achieved a 25% increase in spin transport efficiency and a 20% enhancement in memory device performance. Our results demonstrate the crucial role of optimizing device length, material quality, and interface engineering in achieving efficient spin transport and improved memory device performance, paving the way for the development of high-performance spin-based technologies.

Resetting the Drift of Oxygen Vacancies in Ultrathin HZO Ferroelectric Memories by Electrical Pulse Engineering

Ferroelectric HfO2‐based films incorporated in nonvolatile memory devices offer a low‐energy, high‐speed alternative to conventional memory systems. Oxygen vacancies have been rigorously cited in literature to be pivotal in stabilizing the polar noncentrosymmetric phase responsible for ferroelectricity in HfO2‐based films. Thus, the ability to regulate and control oxygen vacancy migration in operando in such materials would potentially offer step changing new functionalities, tunable electrical properties, and enhanced device lifespan. Herein, a novel in‐ operando approach to control both wake‐up and fatigue device dynamics is reported. Via clever design of short ad hoc square electrical pulses, both wake‐up can be sped up and both fatigue and leakage inside the film can be reduced, key factors for enhancing the performance of memory devices. Using plasmon‐enhanced photoluminescence and dark‐field spectroscopy (sensitive to <1% vacancy variation), evidence that the electrical pulses give rise to oxygen vacancy redistribution is provided and it is shown that pulse engineering effectively delays wake‐up and reduces fatigue characteristics of the HfO2‐based films. Comprehensive analysis also includes impedance spectroscopy measurements, which exclude any influence of polarization reversal or domain wall movement in interpretation of results.

Suppression of crystallization process in Atomic Layer Deposited hafnium oxide films

Research on the deposition process of atomic layer deposition (ALD) of hafnium oxide thin films is important because it enhances the performance of nonvolatile memory devices and optical coatings and contributes significantly to advancements within the semiconductor industry. In this study, the alternating deposition of tetrakis(dimethylamido) hafnium and cyclopentadienyl tris(dimethylamino) hafnium precursors was studied. Moreover, this method allows for modulation of the refractive index, surface morphology, preferred orientation and phases of the material. Theoretical calculations revealed that the two precursors selectively adsorb on different crystal planes during the ALD process, elucidating the mechanism behind their preferred orientations. This study reports a method for regulating the phase development of thin films. The crystallization of the hafnium oxide thin films was suppressed by controlling the conditions of deposition.

In-situ crystallization of rutile-phased TiO2 via the template effect using MoO2 electrode for the metal-insulator-metal capacitor applications

This study investigates the viability of TiO2 as a high-k material in metal-insulator-metal (MIM) capacitors, essential components influencing semiconductor memory device performance. Traditional materials like ZrO2 and HfO2 face intrinsic limitations, prompting exploration into TiO2's potential, particularly in its rutile crystalline structure with a remarkable dielectric constant of 170. Leveraging atomic layer deposition (ALD), TiO2 emerges as a promising candidate for MIM capacitors. The study focuses on the practical application of a MoO2 electrode in TiO2 dielectric film MIM capacitors, demonstrating its potential to induce rutile crystallization in both MoO2 and TiO2 while suppressing morphology degradation. Insights into the mechanism of TiO2 rutile crystallization contribute to the development of an optimized MoO2/TiO2-based MIM capacitor, offering a significant advancement in addressing challenges and improving the performance of next-generation semiconductor memory devices.

Nanocrystal Materials for Resistive Memory and Artificial Synapses: Progress and Prospects.

Resistive random-access memory (RRAM) is considered to be the most promising next-generation non-volatile memory because of its low cost, low energy consumption, and excellent data storage characteristics. However, the on/off (SET/RESET) voltages of RRAM are too random to replace the traditional memory. Nanocrystals (NCs) offer an appealing option for these applications since they combine excellent electronic/optical properties and structural stability and can address the requirements of low-cost, large-area, and solution-processed technologies. Therefore, the doping NCs in the function layer of RRAM are proposed to localize the electric field and guide conductance filaments (CFs) growth. The purpose of this article is to focus on a comprehensive and systematical survey of the NC materials, which are used to improve the performance of resistive memory (RM) and optoelectronic synaptic devices and review recent experimental advances in NC-based neuromorphic devices from artificial synapses to light-sensory synaptic platforms. Extensive information related to NCs for RRAM and artificial synapses and their associated patents were collected. This review aimed to highlight the unique electrical and optical features of metal and semiconductor NCs for designing future RRAM and artificial synapses. It was demonstrated that doping NCs in the function layer of RRAM could not only improve the homogeneity of SET/RESET voltage but also reduce the threshold voltage. At the same time, it could still increase the retention time and provide the probability of mimicking the bio-synapse. NC doping can significantly enhance the overall performance of RM devices, but there are still many problems to be solved. This review highlights the relevance of NCs for RM and artificial synapses and also provides a perspective on the opportunities, challenges, and potential future directions.

Ce-doping at Mn site to enhance resistive switching performance of spinel MnCo2O4 resistive random access memory devices

The spinel Ce-doping MnCo2O4 (MCO) thin films were fabricated on Pt/Ti/SiO2/Si substrates for resistive switching (RS) layer using sol-gel spin-coating deposition method. The Pt/Mn0.925Ce0.075Co2O4/Pt (Pt/7.5MCC/Pt) device exhibits stabler and superior bipolar RS performance, the concentrated distribution of Reset/Set voltage as low as – 0.62/1.175 V, good cycle endurance and excellent time retention capability. The improvement in the RS performance of the Pt/7.5MCC/Pt devices can be attributable to the effective limitation of the random formation and rupture of conductive filaments by appropriate Ce doping. The carrier transport mechanism of the device at high resistance state can be dominated by the Schottky emission, whereas the carrier transport mechanism at low resistance state consistent with the Ohmic conduction. This work provides a potential performance improvement approach to design the resistive memory devices for data storage applications.

Self-rectifying resistive switching in MAPbI3-based memristor device

A critical stage in developing high-density memristors is addressing the sneak current within the crossbar architecture. One of the effective strategies to endow the memristive cell with the ability to prevent sneak currents when it is in a low resistance state is to give it an inherent diode, known as a self-rectifying memristive cell. This study demonstrates the Schottky diode inside the MAPbI3-based memristive cell, a consequence of its interaction with the tungsten (W) electrode. The performance of memory devices is reliable with low-voltage operation, a resistance window having over ten of magnitude, and the retention time remains over 104 s. Prominently, the self-rectifying behavior is sustainable over 150 cycles and exhibits a rectification ratio of approximately 102 times. Density functional theory calculation reveals the presence of unoccupied gap states on an interfaced MAPbI3 surface, serving as electron trapping states during the charge transport across the W/MAPbI3 Schottky interface. Consequently, the conduction mechanism is primarily governed by an interfacial-controlled model, notably Schottky emission. This improvement promises to eliminate sneak currents in future crossbar array fabrication.

Exploring non-stoichiometric SiOx thin film for non-volatile memory application

This article explores the electrical performance of capacitive memory and resistive switching (RS) devices based on thin films of a single active layer of Silicon oxide (SiOx). The fabricated device Au/SiOx/p-Si displayed frequency-dependent characteristics ranging from 200 kHz to 1 MHz w.r.t capacitance. The charge trapping nature was also investigated, which revealed a charge storage density (N) of order 1010 cm−2 and a low trapping density of interface (Dit) ∼2.65 × 1011 eV−1 cm−2. Furthermore, the device exhibits bipolar RS behavior while maintaining a stable endurance for 1000 DC sweeping cycles and a good retention period of > 103 s. The major pathway of the conduction mechanism in these devices is attributed to the accumulation of oxygen vacancies near the Au/SiOx interface. The conduction in this device is predominantly governed by trap-mediated space-charge-limited current (SCLC) and ohmic conductions.

Optimized chalcogenide medium for inherently activated resistive switching device

The suitability of thin films of the chalcogenide germanium telluride (GeTex) with various chemical compositions for use as an active medium in a conductive bridge resistive switching memory device with Cu and TiN as the active and counter electrodes, respectively, was examined. Experimental results showed that all of the tested resistive switching devices showed identical current-voltage hysteresis curves for the first and second cycles, the electroforming (EF)-free characteristic, which is favourable for achieving high operational reliability. From a comparative study of different active electrodes, we concluded that the intrinsic electronic traps and diffused Cu ions in the GeTex layer were responsible for the EF-free characteristic. Furthermore, as the Te content increased, the retention characteristics of the programmed resistance state became unstable since the short-range-ordered Te-Te clusters in the GeTex layer caused the Cu conductive filament to dissolve in Cu-Te locally. Experimental results indicated that the chalcogenide materials were good candidates for a highly reliable active layer in a conducting-bridge resistive switching memory device. This report presents various microscopic analysis results to show the superior performance of chalcogenide-based resistive switching memory devices.

Simultaneously ultrafast and robust two-dimensional flash memory devices based on phase-engineered edge contacts

As the prevailing non-volatile memory (NVM), flash memory offers mass data storage at high integration density and low cost. However, due to the ‘speed-retention-endurance’ dilemma, their typical speed is limited to ~microseconds to milliseconds for program and erase operations, restricting their application in scenarios with high-speed data throughput. Here, by adopting metallic 1T-LixMoS2 as edge contact, we show that ultrafast (10–100 ns) and robust (endurance>106 cycles, retention>10 years) memory operation can be simultaneously achieved in a two-dimensional van der Waals heterostructure flash memory with 2H-MoS2 as semiconductor channel. We attribute the superior performance to the gate tunable Schottky barrier at the edge contact, which can facilitate hot carrier injection to the semiconductor channel and subsequent tunneling when compared to a conventional top contact with high density of defects at the metal interface. Our results suggest that contact engineering can become a strategy to further improve the performance of 2D flash memory devices and meet the increasing demands of high speed and reliable data storage.

Effect of Transition Metal Dichalcogenide Based Confinement Layers on the Performance of Phase-Change Heterostructure Memory.

Phase-change random-access memory is a promising non-volatile memory technology. However repeated phase-change operations can cause durability issues owing to defects formed by long-distance atom diffusion. To mitigate these issues, phase-change heterostructure (PCH) devices with confinement material (CM) layers based on transition metal dichalcogenides (TMDs) such as TiTe2 have been proposed. This study implements PCH devices with additional TMDs, including NiTe2 and MoTe2 , alongside TiTe2 , and analyzes their characteristics by examining the differences in the CM layers. The results show that the NiTe2 -based PCH device demonstrates a RESET current of 1.4mA, 38% lower than that of the TiTe2 -based device, enabling low-power operation. Furthermore, the MoTe2 -based PCH device exhibits a cycling endurance exceeding 107 cycles, a five-fold improvement in durability compare with the TiTe2 -based device. The performance differences observe in each PCH device can be attributed to the variation in the material properties, such as the cohesive energy and electrical conductivity, of the TMDs used as the CM layer. These results provide critical clues to improve the performance and reliability of conventional PCH memory devices.

Uncovering the Role of Crystal Phase in Determining Nonvolatile Flash Memory Device Performance Fabricated from MoTe2-Based 2D van der Waals Heterostructures.

Although the crystal phase of two-dimensional (2D) transition metal dichalcogenides (TMDs) has been proven to play an essential role in fabricating high-performance electronic devices in the past decade, its effect on the performance of 2D material-based flash memory devices still remains unclear. Here, we report the exploration of the effect of MoTe2 in different phases as the charge-trapping layer on the performance of 2D van der Waals (vdW) heterostructure-based flash memory devices, where a metallic 1T'-MoTe2 or semiconducting 2H-MoTe2 nanoflake is used as the floating gate. By conducting comprehensive measurements on the two kinds of vdW heterostructure-based devices, the memory device based on MoS2/h-BN/1T'-MoTe2 presents much better performance, including a larger memory window, faster switching speed (100 ns), and higher extinction ratio (107), than that of the device based on the MoS2/h-BN/2H-MoTe2 heterostructure. Moreover, the device based on the MoS2/h-BN/1T'-MoTe2 heterostructure also shows a long cycle (>1200 cycles) and retention (>3000 s) stability. Our study clearly demonstrates that the crystal phase of 2D TMDs has a significant impact on the performance of nonvolatile flash memory devices based on 2D vdW heterostructures, which paves the way for the fabrication of future high-performance memory devices based on 2D materials.