Switching Memory Research Articles

Robust Carbon‐Dot Optical Disks for Orthogonal Amplitude‐Polarization Encryption Storage

AbstractHigh‐capacity steganography is crucial for the secure exchange of massive information. Exploring orthogonally optical recording can significantly improve encryption levels. However, due to the lack of robust media, the hidden data are easy to be cracked or destructed. Herein, carbon dots have the switchable memory function between optical transmittance and polarization state after receiving excitation power adjustment is discovered. A large‐area carbon‐based disk is further constructed which is measured to resist the high‐temperature damage at 423 K for more than 405 h and is estimated to remain stable at room‐temperature (301 K) beyond 2341 years. With the alternated arrangement of the dual functional carbon dots at one region of the disk, only by using an amplitude‐type holographic diffraction key can the polarized pattern be correctly read out. The ultra‐high secure encryption strategy also puts a bright way to the applications of 3D image hiding, permanent data preservation, and anti‐counterfeiting labels.

An efficient device model for ferroelectric thin-film transistors

Ferroelectric thin-film transistors (Fe-TFTs) have promising potential for flexible electronics, memory, and neuromorphic computing applications. Here, we report on a physics-based efficient device model for Fe-TFTs that effectively describes memory switching and device I–V characteristics. This model combines a stochastic multi-domain description of FE switching dynamics with a virtual source treatment of TFT device characteristics. It demonstrates that the memory window of Fe-TFTs depends on the amplitude and duration of the applied voltage pulses, thus suggesting quantitative means of programming and control. Additionally, we introduce a machine-learning-enabled method to automatically generate optimal voltage pulses for accurately programming multiple intermediate FE states, which is crucial for multi-bit memory and neuromorphic computing applications. To showcase the model’s applications, we simulate a 4×4 crossbar array circuit based on Fe-TFTs, highlighting its utility in performing multiply-accumulate computing operations. This small array can achieve a high speed of ∼1.28 tera operations per second (OPS) and a power efficiency of ∼0.43 W/PetaOPS. The model developed here is valuable for exploring the capabilities of Fe-TFTs in future flexible memory and computing technologies.

Numerical solutions of regime-switching functional diffusions with infinite delay

We study a class of diffusion processes which are determined by solutions X(t) to stochastic functional differential equation with infinite memory and random switching represented by Markov chain Λ(t). Under suitable conditions, we adopt Euler-Maruyama method to deal with the convergence of numerical solutions of the corresponding stochastic differential equations. More precisely, we investigate convergence rates in the L 2-norm the stochastic functional differential equation with infinite memory and random switching under the global Lipschitz conditions. Then we also discuss L 2-convergence under the local Lipschitz conditions.

Audio Signal-Stimulated Multilayered HfOx/TiOy Spiking Neuron Network for Neuromorphic Computing.

As the key hardware of a brain-like chip based on a spiking neuron network (SNN), memristor has attracted more attention due to its similarity with biological neurons and synapses to deal with the audio signal. However, designing stable artificial neurons and synapse devices with a controllable switching pathway to form a hardware network is a challenge. For the first time, we report that artificial neurons and synapses based on multilayered HfOx/TiOy memristor crossbar arrays can be used for the SNN training of audio signals, which display the tunable threshold switching and memory switching characteristics. It is found that tunable volatile and nonvolatile switching from the multilayered HfOx/TiOy memristor is induced by the size-controlled atomic oxygen vacancy pathway, which depends on the atomic sublayer in the multilayered structure. The successful emulation of the biological neuron's integrate-and-fire function can be achieved through the utilization of the tunable threshold switching characteristic. Based on the stable performance of the multilayered HfOx/TiOy neuron and synapse, we constructed a hardware SNN architecture for processing audio signals, which provides a base for the recognition of audio signals through the function of integration and firing. Our design of an atomic conductive pathway by using a multilayered TiOy/HfOx memristor supplies a new method for the construction of an artificial neuron and synapse in the same matrix, which can reduce the cost of integration in an AI chip. The implementation of synaptic functionalities by the hardware of SNNs paves the way for novel neuromorphic computing paradigms in the AI era.

Synergistic effects of cellulose nanocrystal on the mechanical and shape memory properties of TPU composites

Cellulose nanocrystal is a nanomaterial that has a large specific surface area, high surface energy, and high strength. As well, it is biocompatible, environmentally friendly, nontoxic, and can be extracted from biomass resources. Because of these features, cellulose nanocrystals can be used to improve the mechanical properties of polymer matrices with a shape memory effect and as a shape memory switch. In this study, a polytrimethylene ether glycol-based thermoplastic polyurethane (TPU)/cellulose nanocrystal (CNC) composite was prepared via an in-situ polymerization process to create a self-healing polymer matrix. Also, the effect of CNC doses in low concentrations (≤2 wt%) on the different properties of the resulting bio-nanocomposite was investigated. The results showed that the introduction of CNCs affects the hydrogen bonding within the polymer matrix and provides better thermal stability in the high temperature range than pure TPU. Furthermore, the samples with 0 wt%, 0.75 wt%, 1 wt%, and 2 wt% of CNC exhibited an increasing trend in tensile strength with values of 11.71 MPa, 18.95 MPa, 17.88 MPa, and 26.18 MPa, respectively, which indicates a remarkable improvement in mechanical strength. The shape memory behavior was also notably prominent in this polymer composite, where the composite containing 2 wt% of CNC showed the fastest recovery time (240 s) at 75 °C with the highest shape retention. Moreover, their flow behavior and deformation capacity were examined through rheology tests. Besides, docking simulations were conducted in silico to assess the interaction of the TPU/CNC composite with the DNA gyrase enzyme. The interaction between CNC/TPU composite and DNA gyrase was meticulously analyzed across 10 distinct conformations, yielding docking scores ranging from −6.5 Kcal/mol to −5.3 Kcal/mol. Overall, the physico-mechanical properties of the TPU/CNC composites were substantially enhanced with the incorporation of nanofillers.

Digital Light Processing Resins with Programmable Shape Memory for Biomedical Applications.

The creation of biodegradable and biocompatible shape memory polymers amenable to biofabrication techniques remains a challenge. The ability to create shape-changing biodegradable objects that are triggered at body temperature opens up possibilities in tissue engineering, minimally invasive surgery, and actuating bioimplants. Merging Digital Light Processing (DLP) printing with shape memory polymers brings us closer to new smart biomedical outcomes. Previously, we developed a poly(caprolactone-co-trimethylenecarbonate) urethane acrylate resin for the DLP fabrication of biodegradable 3D objects. In further studies, we observed that some of these resins possessed shape memory properties, triggered by body temperature (37 °C). In this subsequent study, we explored the shape memory properties and tunability of this resin family via changes in copolymer composition, molecular weight, and identity of the acrylate end-capping unit. We found that we could create a library of shape memory resins, amenable to DLP printing, which allowed the creation of shape-actuating structures with some tunability over the speed of shape memory and mechanical properties. We observed that increased mole fraction of caprolactone in the copolymer and increased molecular weight of the polymer led to a decrease in speed of the shape memory switch. Furthermore, we observed a trade-off between the composition and the end-capping moiety on the mechanical properties of the polymers. These polymeric resins were able to be processed into shapes that were able to perform work, including the release of cargo and grabbing/lifting of an object. This platform now provides a way to tune the speed and mechanical properties of a shape memory DLP object created from common and scalable polymerization techniques. This work ultimately provides a new platform to develop customizable and biodegradable devices capable of actuating and delivery devices for numerous biomedical applications.

No Impairment in Bone Turnover or Executive Functions in Well-Treated Preschoolers with Phenylketonuria-A Pilot Study.

Patients with phenylketonuria (PKU) present signs of impaired executive functioning and bone health in adolescence and adulthood, depending in part on the success of therapy in childhood. Therefore, nine children with well-treated PKU (4-7 years old, 22.2% ♀, seven with a full set of data, two included into partial analysis) and 18 age-, gender- and season-matched controls were analyzed for differences in executive functioning and bone parameters in plasma. Plasma was analyzed with commercially available kits. Cognitive performance in tonic alertness, visuo-spatial working memory, inhibitory control and task switching was assessed by a task battery presented on a touch screen. Regarding cognition, only the performance in incongruent conditions in inhibitory control was significantly better in children with PKU than in controls. No further differences in cognitive tests were detected. Furthermore, no significant difference in the bone turnover markers osteocalcin, undercarboxylated osteocalcin and CTX were detected between children with PKU and controls, while children with PKU had a significantly higher vitamin D concentration (69.44 ± 12.83 nmol/L vs. 41.87 ± 15.99 nmol/L, p < 0.001) and trended towards lower parathyroid hormone concentrations than controls (48.27 ± 15.16 pg/mL vs. 70.61 ± 30.53 pg/mL, p = 0.066). In this small group of well-treated preschoolers with PKU, no impairments in cognitive performance and bone turnover were observed, while vitamin D supplementation of amino acid supplements seems to be sufficient to achieve good vitamin D status.

Evaluating the efficacy of cranial electrotherapy stimulation in mitigating anxiety-induced cognitive deficits

Cranial electrotherapy stimulation (CES) is a form of non-invasive brain stimulation (NIBS) that has demonstrated potential to modulate neural activity in a manner that may be conducive to improved cognitive performance. While other forms of NIBS, such as transcranial direct current stimulation (tDCS), have received attention in the field as potential acute cognitive enhancers, CES remains relatively unexplored. The current study aimed to assess the efficacy of CES in improving acute cognitive performance under normal experimental conditions, as well as during sessions of induced situational anxiety (threat of shock or ToS). To study this question, participants completed a cognitive battery assessing processing speed and distinct aspects of executive functioning (working memory, inhibition, and task switching) in two separate sessions in which they received active and sham CES. Participants were randomly assigned to between subject groups of either situational anxiety (ToS) or control condition (no ToS). We predicted that active CES would improve performance on assessments of executive functioning (working memory, inhibition, and task switching) relative to sham CES under ToS. We did not find any significant effects of ToS, CES, or an interaction between ToS and CES for any measures of executive functioning or processing speed. These findings suggest that a single dose of CES does not enhance executive functioning or processing speed under normal conditions or during ToS.

Low-loss, compact, fibre-integrated cell for quantum memories

We present a low-loss, compact, hollow core optical fibre (HCF) cell integrated with single mode fibre (SMF). The cell is designed to be filled with atomic vapour and used as a component in photonic quantum technologies, with applications in quantum memory and optical switching. We achieve a total insertion loss of 0.6(2) dB at 780 nm wavelength via graded index fibre to ensure efficient mode matching coupled with anti-reflection coatings to minimise loss at the SMF-HCF interfaces. We also present numerical modelling of these interfaces, which can be undertaken efficiently without the need for finite element simulation. We encapsulate the HCF core by coupling to the SMF inside a support capillary, enhancing durability and facilitating seamless integration into existing fibre platforms.

Default mode network shows distinct emotional and contextual responses yet common effects of retrieval demands across tasks.

The default mode network (DMN) lies towards the heteromodal end of the principal gradient of intrinsic connectivity, maximally separated from the sensory-motor cortex. It supports memory-based cognition, including the capacity to retrieve conceptual and evaluative information from sensory inputs, and to generate meaningful states internally; however, the functional organisation of DMN that can support these distinct modes of retrieval remains unclear. We used fMRI to examine whether activation within subsystems of DMN differed as a function of retrieval demands, or the type of association to be retrieved, or both. In a picture association task, participants retrieved semantic associations that were either contextual or emotional in nature. Participants were asked to avoid generating episodic associations. In the generate phase, these associations were retrieved from a novel picture, while in the switch phase, participants retrieved a new association for the same image. Semantic context and emotion trials were associated with dissociable DMN subnetworks, indicating that a key dimension of DMN organisation relates to the type of association being accessed. The frontotemporal and medial temporal DMN showed a preference for emotional and semantic contextual associations, respectively. Relative to the generate phase, the switch phase recruited clusters closer to the heteromodal apex of the principal gradient-a cortical hierarchy separating unimodal and heteromodal regions. There were no differences in this effect between association types. Instead, memory switching was associated with a distinct subnetwork associated with controlled internal cognition. These findings delineate distinct patterns of DMN recruitment for different kinds of associations yet common responses across tasks that reflect retrieval demands.

Analytical Release Voltage Model of Monolithic 3-D Integrated Nanoelectromechanical Memory Switches

Analytical Release Voltage Model of Monolithic 3-D Integrated Nanoelectromechanical Memory Switches

A comprehensive investigation of Bi2O3 on the physical, structural, optical, and electrical properties of K2O.ZnO.V2O5.B2O3 glasses

The multi-component glass system has a composition of 10K2O–10ZnO–55 B2O3–(25–x)V2O5–xBi2O3 (x = 4, 5, 7.5, 9, 10 mol%) are synthesized by the melt-quenching method. Using X-ray diffraction examination, the amorphous phase in the material was confirmed. The physical characteristics of the produced compositions are examined using density (D) and molar volume (Vm). Calculations of physical properties showed that adding Bi2O3 from 4 to 10 mol% increased the glass density from 2.7878 to 3.3617 g cm−3 and decreased the molar volume from 40.4196 to 38.5895 cm3/mol. Studies of glass samples using the FTIR show bands of absorption for oxides in different structural groups. Octahedral [BiO6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{BiO}}}_{6}$$\\end{document}], [BO4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{BO}}}_{4}$$\\end{document}], and tetrahedral [BO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{BO}}}_{3}$$\\end{document}] structural units are observed in the present glass matrices. The cutoff wavelength (λC\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\lambda }_{C}$$\\end{document}), and optical band gap energy were determined using UV absorption spectra. The increase in non-bridging oxygens can be linked to the decrease in optical band gap energy (Eopt\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${E}_{opt}$$\\end{document}) (direct and indirect) and the increase in cutoff wavelength with an increase in Bi2O3 content. This is attributed to the existence of bismuth ions and the creation of non-bridging oxygens. Besides that, the values of optical parameters, viz., optical electronegativity, refractive index, and molar refractivity, are calculated. The metallization criterion values are less than 1 and the glass samples exhibit an increased tendency towards metallization. Both the conductivity and the dielectric constant increase with the rise in Bi2O3 content, however, the dielectric loss and the impedance reduce. The behavior and values of conductivity for the studied glasses reveal the semiconducting properties of all glass samples. These results suggest that the produced glass samples may be employed as amorphous semiconductors in electronics and memory switching devices.

Exploration of electrode-modulated memory and threshold switching behaviour in Se-Te-Sn thin film devices

Due to their potential use in high-density, three-dimensional stackable cross-point array structures, the electrical switching ability of chalcogenide glasses has captured a lot of attention. Herein, the switching behaviour of unique Se86-xTe14Snx (x = 0, 2, 4, 6) chalcogenide glassy alloys in the form of a thin film were investigated. The electrode modulated dual functionality in switching was achieved by employing Aluminium (Al) and Silver (Ag), as top electrodes. The films with Al/Se86-xTe14Snx/Al interface exhibited memory-type switching due to the phase-changing properties of the material. The threshold voltage (Vth) decreased linearly from 12.75 V to 4.2 V at room temperature as Sn concentration in the glass increased. On the other hand, when the top electrode was replaced with Ag, the Ag/Se86-xTe14Snx/Al interface acted as a programmable metallization cell (PMC) showing threshold-switching properties. Ag/Se82Te14Sn4/Al thin film of thickness 200 nm showed promising results as a material for a unidirectional selector, due to the formation of temporary Ag filament inside chalcogenide material. The composition showed high selectivity (∼104), high endurance (>104 cycles), and low threshold voltage (∼1.6 V). The ability of the composition to exhibit electrode-dependent memory and threshold-switching phenomena makes the material an interesting case.

Multifunctional polyphosphazene grafted with triphenylamine and aminostilbene chromophore for electrochromic and sensor application

In this paper, a sequence of polyphosphazenes (PPZs) as electrochromic (EC) and sensor materials have been designed and synthesized by introducing chromophores, (4-(diphenyl amino)phenyl) methanol (CH1) for PPZ1, 3-(4-(dimethyl amino) phenyl)-2-(4hydroxyphenyl) acrylonitrile (CH2) for PPZ2, and CH1 and CH2 for PPZ3 into the main chain. In terms of EC performance, PPZ1 shows the best EC performance among the three PPZs which can achieve 60 % optical contrast at 690 nm with good cyclic stability within 1000 s and fast switching response time (tcolor/tbleach = 1.2 s/0.6 s). Compared to PPZ1, the oxidation potential of PPZ3 is reduced compared to PPZ1. PPZ2 and PPZ3 as sensors are more sensitive for the detection of 2,4,6-trinitrophenol (TNP) and trifluoroacetic acid (TFA) compared to PPZ1. What's more, PPZs can be used in memory devices with non-volatile flash memory performance and switching current ratios of 103:102.4:1, 104.7:101.3:1 and 103.5.:100.6:1 respectively. Therefore, PPZs have the promising prospect in optoelectronic field.

Inkjet printed IGZO memristors with volatile and non-volatile switching

Solution-based memristors deposited by inkjet printing technique have a strong technological potential based on their scalability, low cost, environmentally friendlier processing by being an efficient technique with minimal material waste. Indium-gallium-zinc oxide (IGZO), an oxide semiconductor material, shows promising resistive switching properties. In this work, a printed Ag/IGZO/ITO memristor has been fabricated. The IGZO thickness influences both memory window and switching voltage of the devices. The devices show both volatile counter8wise (c8w) and non-volatile 8wise (8w) switching at low operating voltage. The 8w switching has a SET and RESET voltage lower than 2 V and − 5 V, respectively, a retention up to 105 s and a memory window up to 100, whereas the c8w switching shows volatile characteristics with a low threshold voltage (Vth < − 0.65 V) and a characteristic time (τ) of 0.75 ± 0.12 ms when a single pulse of − 0.65 V with width of 0.1 ms is applied. The characteristic time alters depending on the number of pulses. These volatile characteristics allowed them to be tested on different 4-bit pulse sequences, as an initial proof of concept for temporal signal processing applications.

Forecasting conditional volatility based on hybrid GARCH-type models with long memory, regime switching, leverage effect and heavy-tail: Further evidence from equity market

The properties of clustering, long memory, switching regime, leverage effect and heavy tail in volatility dynamic behavior are induced by important stylized facts in financial markets. There is still a controversy whether incorporating these properties could improve the modelling and forecasting performance of volatility. We construct hybrid volatility models via three perspectives including short memory, long memory and Markov switching GARCH with leverage effect and heavy tail, and empirically compare their performance of in-sample estimation, out-of-sample forecast and risk measurement based on trading data of Chinese equity market index. The out-of-sample forecast results indicate that the FIEGARCH model with innovation distribution of GED outperforms the competing models, and the backtesting results of VaR and ES confirm that this model performs well in the application of risk measurement.

Dysphagia Intervention in Patient with Diffusion Axon Injury with Bilateral Frontal Lobe Contusion: A Case Report

Introduction: Traumatic brain injury (TBI) is a leading cause of chronic neurologic disability. Damage often affects the frontal lobes, and thus the most frequent cognitive sequelae are deficits in the prefrontal cortex (PFC)-dependent functions, such as attention, working memory, social behavior, mental flexibility, and task switching. Objective: The goal of this case report is to highlight the assessment and intervention of the dysphagia program. Case Report: The patient was diagnosed with diffuse axonal injury with bilateral frontal lobe contusion. The patient is receiving care in the Physical Medicine and Rehabilitation (PMR) unit, where they are undergoing physiotherapy occupational therapy, and speech therapy. Results: Speech Assessment revealed deviated voice and resonance characteristics with Substitution &amp; Distortion of speech sounds. Swallowing assessment revealed Oro-pharyngeal Dysphagia. The patient was also undergoing Chemotherapy and Radiation-therapy. Recommendations for further follow-ups for speech &amp; swallowing therapy and other medical management were made. Conclusion: This study is useful in creating evidence regarding the assessment &amp; rehabilitation of Speech and swallowing in patients undergoing hemi-glossectomy. It also emphasizes the input from other medical professionals as an interdisciplinary team member.

A nanoscale study of hafnium oxide resistive memory switching dynamics

This paper deals with the set and reset time measurements of a resistive memory consisting of a Ti/TiN/HfO2 layer stack contacted with the tip of a conductive atomic force microscope in ultra high vacuum. We present measurements of the set and reset switching times in voltage pulse regime for different voltages and compliance currents. The experimental results are well reproduced by simulation. We derive analytical expressions for the set and reset times as function of experimental conditions. The effect of voltage and current on reset and set switching times is then discussed with the help of their analytical expressions, which are also applied on standard devices characteristics.

Highly reliable bipolar resistive switching of tantalum oxide-based memory using Al2O3 diffusion barrier layers

We present a novel bipolar resistive switching memory based on TaOx, featuring a Ru/Al2O3/Ta2O5/TaOx/Al2O3/W structure. Thin Al2O3 layers play a crucial role as diffusion barriers, preventing undesirable interfacial reactions at the top and bottom interfaces. They support the stable formation of the Schottky barrier near the Ru top electrode through redox reactions during operation, resulting in highly reliable bipolar resistive switching. The device exhibits excellent memory performance, including a fast operation speed (∼10 ns), good switching endurance (∼106 cycles), and robust data retention (>104 s at 200 °C).

Dynamic all-optical memory switching based on atomic optical bistable behavior in a three level Λ-type atomic system

We theoretically investigate the atomic optical bistability (AOB) in a three-level Λ-type atomic system confined in a unidirectional optical ring cavity. The role of the intensity or detuning of the control field on AOB is explored, and results show that absorption, dispersion, and nonlinearity can be modified significantly by the control field due to quantum coherence and interference in multilevel atomic systems. Thus, tuning the intensity or detuning of the control field can manipulate the switch-up and switch-down thresholds, as well as the area of the bistable hysteresis loop. According to the controllability of AOB, we design various schemes to realize dynamical all-optical switching between the high and low outputs of two bistable curves for a fixed cavity input. In addition, dynamical all-optical memory switching can be implemented by adding a pulse sequence for the intensity or detuning of the control field. For appropriate parameters, such as the cooperative coefficient, the extinction ratio of the switching can be improved dramatically.