Resistance State Research Articles

The Fabrication of Polyimide-Based Tunable Charge Traps Ternary Memristors Doped with Ni-Co Coated Carbon Composite Nanofibers

In the dynamic fields of information science and electronic technology, there is a notable trend towards leveraging carbon materials, favored for their ease of synthesis, biocompatibility, and abundance. This trend is particularly evident in the development of memristors, benefiting from the unique electronic properties of carbon to enhance device performance. This study utilizes sensitized chemical evaporation and spin-coating carbonization techniques to fabricate nickel-cobalt coated carbon composite nanofibers (SC-NCMNTs). Novel polyimide (PI) matrix composite memory devices were fabricated using in situ polymerization technology. Transmission electron microscopy (TEM) and micro-Raman spectroscopy analyses validated the presence of dual interface structures located between the Ni-Co-MWNTs, carbon composite nanofibers, and PI matrix, revealing a significant number of defects within the SC-NCMNTs/PI composite films. Consequently, this results in a tunable charge trap-based ternary resistive switching behavior of the composite memory devices, exhibiting a high ON/OFF current ratio of 104 and a retention time of 2500 s at an operating voltage of less than 3 V. The mechanism of resistive switching is thoroughly elucidated through a comprehensive charge transport model, incorporating molecular orbital energy levels. This study provides valuable insights for the rational design and fabrication of efficient memristors characterized by multilevel resistive switching states.

Reset transition in HfO2-Based memristors using a constant power signal

Memristors, also known as resistive switching devices, have great potential for applications in memory and neuromorphic systems. Understanding the switching mechanisms is crucial since ReRAM memories need to operate at high frequencies. It is known the reset transition is dominated by the conductive filament Joule heating. We have studied the reset transition in TiN/Ti/HfO2/W metal–insulator–metal memristors by applying constant power signals to different initial filament thicknesses, which were obtained using different initial low resistance states. The results show that power value controls the reset times, decreasing when the power is increased. On the other hand, larger resistances lead to faster reset transitions. These measurements have allowed us to obtain a value of the thermal resistance of the conductive filament. Moreover, we have observed the reset times as a function of the initial resistance and the power lies on a common plane, which allows us to estimate the transition time by fixing an initial resistance and a power value.

Bioengineered Extracellular Vesicles Delivering siMDM2 Sensitize Oxaliplatin Therapy Efficacy in Colorectal Cancer.

Oxaliplatin (OXA) is the first-line drug for the treatment of colorectal cancer (CRC), and susceptibility to drug resistance affects patient prognosis. However, the exact underlying mechanisms remain unclear. Platinum-acquired resistance in CRC is a continuous transition process; though, current research has mainly focused on the end state of drug resistance, and the early events of drug resistance have been ignored. In this study, single-cell transcriptome sequencing is combined with a dynamic network biomarker (DNB), and found that the functional inhibition of the mitochondrial electron transport chain complex I occur early in the development of attained resistance to OXA in CRC cells, as evidenced by a decrease in the levels of subunit proteins, primarily NDUFB8. Specifically, the mouse double minute 2 homologue (MDM2) mediates the ubiquitination and degradation of NDUFB8, reducing intracellular reactive oxygen species (ROS) generation under chemotherapeutic stress, consequently contributing to drug resistance. Based on this, the study constructs engineered extracellular vesicles carrying siMDM2 by electroporation and validates the application of EV-siMDM2 to improve the efficacy of OXA-based chemotherapy by inhibiting the MDM2/NDUFB8/ROS signaling axis in patient-derived xenograft (PDX) and hepatic and pulmonary metastasis mouse models, thus providing new ideas and an experimental basis for the platinum-resistant treatment of CRC.

Genetic aspects of taste formation

The article discusses the molecular genetic basis of taste development which determines the peculiarity of perception of sweet, salty, sour, bitter and high-protein food (umami). The genes TAS1R3, FTO, GLUT2, FGF21, GNAT3 are responsible for individual perception of sugar volume. Serum FGF21 levels are significantly elevated in obese patients and in patients with type 2 diabetes mellitus which presumably indicates a state of resistance to FGF21. Given the role of refined sugars in the development of diseases, the use of foods with a reduced content or complete absence of added sugar is a worldwide trend, especially necessary in the nutrition of children. During genome-wide sequencing for 39 patients aged 15-18 years, FGF21 gene polymorphism was detected in 27 adolescents (69 %) without gender identity. Almost all patients with FGF21 gene polymorphism showed a high addiction to sweet foods. Currently, the existence of a sixth taste is being debated, it is ammonium chloride, whose receptors are regulated by the Otop1 gene which is also responsible for the identification of sour taste.

Field-Free Superconducting Diode Effect and Magnetochiral Anisotropy in FeTe0.7Se0.3 Junctions with the Inherent Asymmetric Barrier.

Nonreciprocal electrical transport, characterized by an asymmetric relationship between the current and voltage, plays a crucial role in modern electronic industries. Recent studies have extended this phenomenon to superconductors, introducing the concept of the superconducting diode effect (SDE). The SDE is characterized by unequal critical supercurrents along opposite directions. Due to the requirement on broken inversion symmetry, the SDE is commonly accompanied by electrical magnetochiral anisotropy (eMCA) in the resistive state. Achieving a magnetic-field-free SDE with field tunability is pivotal for advancements in superconductor devices. Conventionally, field-free SDE has been achieved in Josephson junctions by intentionally intercalating an asymmetric barrier layer. Alternatively, internal magnetism was employed. Both approaches pose challenges in the selection of superconductors and fabrication processes, thereby impeding the development of SDE. Here, we present a field-free SDE in FeTe0.7Se0.3 (FTS) junction with eMCA, a phenomenon absent in FTS single nanosheets. The field-free property is associated with the presence of a gradient oxide layer on the upper surface of each FTS nanosheet, while eMCA is linked to spin splitting arising from the absence of inversion symmetry. Both SDE and eMCA respond to magnetic fields with distinct temperature dependencies. This work presents a versatile and straightforward strategy for advancing superconducting electronics.

Chemical and Resistive Switching Properties of Elaeodendron buchananii Extract-Carboxymethyl Cellulose Composite: A Potential Active Layer for Biodegradable Memory Devices.

Biodegradable electronic devices play a crucial role in addressing the escalating issue of electronic waste accumulation, which poses significant environmental threats. In this study, we explore the utilization of a methanol-based extract of the Elaeodendron buchananii plant blended with a carboxymethyl cellulose biopolymer to produce a biodegradable and environmentally friendly functional material for a resistive switching memory system using silver and tungsten electrodes. Our analyses revealed that these two materials chemically interact to generate a perfect composite with near semiconducting optical bandgap (4.01 eV). The resultant device exhibits O-type memory behavior, with a low ON/OFF ratio, strong endurance (≥103 write/erase cycles), and satisfactory (≥103) data retention. Furthermore, through a comprehensive transport mechanism analysis, we observed the formation of traps in the composite that significantly improved conduction in the device. In addition, we established that altering the voltage amplitude modifies the concentration of traps, leading to voltage amplitude-driven multiple resistance states. Overall, our findings underscore the potential of functionalizing polymers that can be functionalized by incorporating plant extracts, resulting in biodegradable and nonvolatile memory devices with promising performance metrics.

Threshold Switching and Resistive Switching in SnO2-HfO2 Laminated Ultrathin Films

Polycrystalline SnO2-HfO2 nanolaminated thin films were grown by atomic layer deposition (ALD) on SiO2/Si(100) and TiN substrates at 300 °C. The samples, when evaluated electrically, exhibited bipolar resistive switching. The sample object with a stacked oxide layer structure of SnO2 | HfO2 | SnO2 | HfO2 additionally exhibited bidirectional threshold resistive switching properties. The sample with an oxide layer structure of HfO2 | SnO2 | HfO2 displayed bipolar resistive switching with a ratio of high and low resistance states of three orders of magnitude. Endurance tests revealed distinguishable differences between low and high resistance states after 2500 switching cycles.

A multilevel resistive switching memristor based on flexible organic–inorganic hybrid film with recognition function

Abstract Brain-inspired neuromorphic computing systems fueled the emergence of memristor-based artificial synapses, however, conventional silicon-based devices restricted their usage in the wearable field because of their difficulty in bending. To tackle the above challenge, a vertically structured flexible memristor with aluminum-based hydroquinone organic–inorganic hybrid film and Al2O3 as the functional layer, ITO and Pt as the bottom and top electrodes, and PET as the substrate has been developed utilizing molecular/atomic layer deposition to achieve a tradeoff between the resistive transition properties and the flexibility of memristors. The obtained devices combine stable resistive switching behavior and flexibility, showing high switching ratio of 103, better retention (up to 105 s) and endurance properties (up to 104 cycles), and robustness at radius of curvature of 4.5 mm after 104 bending cycles. Furthermore, the presence of multilevel resistive states in these devices ensures that the memristor can emulate synaptic properties such as paired-pulse facilitation, transition from short-term plasticity to long-term plasticity, long-term potentiation and depression, and spike-time-dependent plasticity. The resistive switching mechanism and the role of the bending state on the electrical performance of the device are explored. The fully connected artificial neural network based on the memristor can achieve a recognition accuracy of 90.2% for handwritten digits after training and learning. Flexible memristor will bring feasible advances to the integration of neuromorphic computing and wearable functionality.

Intrinsic Josephson junction characteristics of Nd2-xCexCuO4 /SrTiO3 epitaxial films

The current-voltage (I-V) properties along the c axis on Nd2-xCexCuO4/SrTiO3 epitaxial films with x = 0.145, 0.15 were investigated. For all the samples it has been established that the I-V characteristics exhibit several resistive branches, which correspond to the resistive states of individual Josephson junctions. The results confirm the idea of a tunneling mechanism between the CuO2 layers (superconductor - insulator - superconductor junction) for the investigated Nd2-xCexCuO4 compound. The I-V dependence of this compound with x = 0.15 points out on the nonmonotonic nature of the d-wave or anisotropic s-wave symmetry order parameter associated with the coexistence of superconductivity and antiferromagnetic fluctuations.

A Violet‐Light‐Responsive ReRAM Based on Zn2SnO4/Ga2O3 Heterojunction as an Artificial Synapse for Visual Sensory and In‐Memory Computing

AbstractDue to the imitation of the neural functionalities of the human brain via optical modulation of resistance states, photoelectric resistive random access memory (ReRAM) devices attract extensive attraction for synaptic electronics and in‐memory computing applications. In this work, a photoelectric synaptic ReRAM (PSR) of the structure of ITO/Zn2SnO4/Ga2O3/ITO/glass with a simple fabrication process is reported to imitate brain plasticity. Electrically induced long‐term potentiation/depression (LTP/D) behavior indicates the fulfillment of the fundamental requirement of artificial neuron devices. Classification of three‐channeled images corrupted with different levels (0.15–0.9) of Gaussian noise is achieved by simulating a convolutional neural network (CNN). The violet light (405 nm) illumination generates excitatory post synaptic current (EPSC), which is influenced by the persistent photoconductivity (PPC) effect after discontinuing the optical excitation. As an artificial neuron device, PSR is able to imitate some basic neural functions such as multi‐levels of photoelectric memory with linearly increasing trend, and learning‐forgetting‐relearning behavior. The same device also shows the emulation of visual persistency of optic nerve and skin‐damage warning. This device executes high‐pass filtering function and demonstrates its potential in the image‐sharpening process. These findings provide an avenue to develop oxide semiconductor‐based multifunctional synaptic devices for advanced in‐memory photoelectric systems.

Schottky barrier memory based on heterojunction bandgap engineering for high-density and low-power retention

Dynamic random-access memory (DRAM) has been scaled down to meet high-density, high-speed, and low-power memory requirements. However, conventional DRAM has limitations in achieving memory reliability, especially sufficient capacitance to distinguish memory states. While there have been attempts to enhance capacitor technology, these solutions increase manufacturing cost and complexity. Additionally, Silicon-based capacitorless memories have been reported, but they still suffer from serious difficulties regarding reliability and power consumption. Here, we propose a novel Schottky barrier memory (SBRAM), which is free of the complex capacitor structure and features a heterojunction based on bandgap engineering. SBRAM can be configured as vertical cross-point arrays, which enables high-density integration with a 4F2 footprint. In particular, the Schottky junction significantly reduces the reverse leakage current, preventing sneak current paths that cause leakage currents and readout errors during array operation. Moreover, the heterojunction physically divides the storage region into two regions, resulting in three distinct resistive states and inducing a gradual current slope to ensure sufficient holding margin. These states are determined by the holding voltage (Vhold) applied to the programmed device. When the Vhold is 1.1 V, the programmed state can be maintained with an exceptionally low current of 35.7 fA without a refresh operation.

Effect of SiCN thin film interlayer for ZnO-based RRAM.

This study investigates the effect of silicon carbon nitride (SiCN) as an interlayer for ZnO-based resistive random access memory (RRAM). SiCN was deposited using plasma-enhanced chemical vapor deposition (PECVD) with controlled carbon content, achieved by varying the partial pressure of tetramethylsilane (4MS). Our results indicate that increasing the carbon concentration enhances the endurance of RRAM devices but reduces the on/off ratio. Devices with SiCN exhibited lower operating voltages and more uniform resistive switching behavior. Oxygen migration from ZnO to SiCN is examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses, promoting the formation of conductive filaments (CFs) and lowering set voltages. Additionally, we examined the impact of top electrode oxidation on RRAM performance. The oxidation of the Ti top electrode was found to reduce endurance and increase low resistive state (LRS) resistance, potentially leading to device failure through the formation of an insulating layer between the electrode and resistive switching material. The oxygen storage capability of SiCN was further confirmed through high-temperature stress tests, demonstrating its potential as an oxygen reservoir. Devices with a 20 nm SiCN interlayer showed significantly improved endurance, with over 500 switching cycles, compared to 62 cycles in those with a 5 nm SiCN layer. However, the thicker SiCN layer resulted in a notably lower on/off ratio due to reduced capacitance. These findings suggest that SiCN interlayers can effectively enhance the performance and endurance of ZnO-based RRAM devices by acting as an oxygen reservoir and mitigating the top electrode oxidation effect.

7492 Fibroblast Growth Factor 21 In The Diagnosis And Treatment Of Metabolic Disorders

Abstract Disclosure: H.M. Heshmati: None. H.S. Abu-Lebdeh: None. Background: Fibroblast growth factor 21 (FGF21), a member of the human FGF superfamily, is a 181 amino acid peptide hormone primarily produced by the liver. The gene of FGF21, located on chromosome 19, was cloned in 2000. FGF21 is involved in the maintenance of metabolic homeostasis. This review presents an update on the relevance of FGF21 in the diagnosis and treatment of metabolic disorders including obesity, nonalcoholic fatty liver disease (NAFLD), dyslipidemia, and type 2 diabetes. Methods: A systematic search of literature was conducted using the search terms fibroblast growth factor 21, obesity, nonalcoholic fatty liver disease, dyslipidemia, and type 2 diabetes. Results: FGF21 is a stress hormone with effects on energy expenditure and metabolism of lipids and glucose. FGF21 exerts its endocrine action in the central nervous system and adipose tissue. The serum FGF21 levels in normal subjects increase with aging. Stressful conditions (e.g., fasting status, protein restriction, exercise, metabolic disorders, kidney diseases, cardiovascular diseases, and sepsis) increase FGF21 secretion. Serum FGF21 levels are increased in obesity, NAFLD, dyslipidemia, and type 2 diabetes. Some of these patients may have a state of FGF21 resistance. The resistance to FGF21 is related, at least in part, to the presence of high circulating levels of fibroblast activation protein, a protease that inactivates FGF21. It has been suggested that the exercise-induced weight loss can be due to increased FGF21 secretion and decreased FGF21 resistance in adipose tissue. Serum FGF21 level has the potential to be used as a biomarker for early diagnosis of metabolic disorders (e.g., NAFLD and type 2 diabetes). Based on different metabolic properties of FGF21, FGF21-based therapy has been considered as an attractive approach for the treatment of metabolic disorders. Since native FGF21 has poor pharmacodynamic properties (e.g., short half-life and proteolytic cleavage by proteases), long-acting FGF21 analogs (e.g., LY2405319, PF-05231023, pegozafermin, AKR-001, and LLF580) have been synthesized and tested in clinical trials for the treatment of obesity, NAFLD, dyslipidemia, and type 2 diabetes. The available results show that FGF21 analogs can reduce body weight, liver fat, blood lipids, and fasting insulin/insulin resistance. Overall, the treatment with these analogs is safe and well tolerated. Conclusion: FGF21 is a predominantly liver-derived peptide hormone regulating energy expenditure and metabolism of lipids and glucose. Serum FGF21 levels are increased in several metabolic disorders including obesity, NAFLD, dyslipidemia, and type 2 diabetes. FGF21 is an attractive target for the treatment of these metabolic disorders. Despite some promising results observed with the use of FGF21 analogs, more clinical studies are needed before recommending FGF21-based therapies in metabolic disorders. Presentation: 6/2/2024

Tunable luminous color of LEDs achieved through integrating reliable multilevel RRAM

We developed a color-modulated light-emitting device (LED) by the integration of a p-GaN/n-ZnO heterojunction with reliable resistive random access memory (RRAM) and demonstrated a multi-function integrated device with the adjustable electroluminescence (EL) color by modulating the injection current according to the multiple resistance states. As a critical foundation of an integrated device, reliable operation was achieved by introducing an AlOx layer into HfOx RRAM as an adjustment of the resistive switching endurance. Eventually, the EL color of LED was effectively regulated by modulating the compliance current of RRAM. Thanks to the high uniformity, this modulated LED may be a promising candidate for the application of low-cost and high-density LED displays without complicated structures and techniques, and it can provide a feasible approach for the realization of multilevel resistance state feedback from varied EL color in the future.

Wide-bandgap semiconductor SiC-based memristors fabricated entirely by electron beam evaporation for artificial synapses

The combination of high-performance materials and simplified multilayer fabrication processes can promote the rapid and high-quality development of memristors. In this work, we proposed wide-bandgap semiconductor silicon carbide (SiC)-based memristors fabricated entirely by electron beam evaporation technology. The Cu/SiC/Pt structure was fabricated on a 2-inch intrinsic silicon substrate, which can achieve a transition from volatility to non-volatility. Devices had a low and symmetric switching voltage of ±0.5 V, an endurance of >200 cycles, a retention of >103 s, an ON/OFF ratio of ∼103, and can achieve at least 6 different stable resistance states. The combined effects of traps and Cu conductive filaments caused the current to change abruptly during switching, while also possessing excellent synaptic plasticity and pulse programming ability. Our work demonstrated that wide-bandgap semiconductor SiC is a promising candidate for advanced memristors.

ESTUDIO DE LA RESPUESTA I-V EN CELDAS DE MEMORIA DESb70Te30

Chalcogenide glasses are within the group of phase change materials and are promising in their application to non-volatile electronic memories. Under electrical pulses, they can circulate between two amorphous and crystalline structural states that are well differentiated in their conductivity. Assuming that the phase change mechanisms depend on the energy per unit volume delivered to the sensitive material, it is desirable to build cells on a micrometer scale, also considering that they could eventually be integrated into microelectronic manufacturing processes. In a previous work, we observed an abrupt decrease in the resistance of Sb70Te30base thin films deposited by laser ablation in a temperature range of approximately 445 K when the sample is heated at low rates. From the results of differential scanning calorimetry and X-ray diffraction on samples obtained by the same method, we associate the change in resistivity with the crystallization process. In this work, we build micrometric devices with rectangular surface with Sb70Te30assensitive material, deposited on coplanar electrodes with spacing L (8 and 16μm) and width W (4, 8, 16, 32 and 64μm). We measure the voltage response of the devices when excited by scanning of increasing current and, between consecutive scanning, we measure the remaining resistance by applying a constant voltage value. In curves I-V, we identify a transformation from the original state to one of lower resistance, attributable to crystallization, but it was not possible to perform the reverse transformation to a state of higher resistance. Starting from the lack of knowledge about the conductivity of the material, we simulate the electric field in the cell using the Finite Element Method. The electrical conductivity of the chalcogenide glass in its initial state (amorphous) was estimated by adjusting its value in the simulations with different geometries, minimizing the difference between the measured and simulated resistances.

Bias voltage modulated electric transport properties in Fe65Co35/Hf0.5Zr0.5O2 films

We demonstrate the bias voltage modulated electric transport properties in Fe65Co35 (FeCo) films deposited on Hf0.5Zr0.5O2 (HZO) films. Intrinsic multiferroicity have been characterized for the FeCo/HZO heterostructures by analyzing the ferroelectric polarizations and imaging the magnetic domains. We show that, upon the application of bias voltages on the FeCo/HZO heterostructures, the current-voltage (I-V) curves of FeCo films can be regulated, giving rise to different resistance states, enabled partly by strain-mediated magnetoelectric coupling effect. The strain coupling effect between HZO and FeCo films is elucidated by simulating the volumetric strain of the FeCo/HZO films under the action of applied voltages. Through additional analysis, the bias voltage modulated electric transport properties could also be linked with charge-mediated magnetoelectric coupling effect. We anticipate that our work will inspire further studies on low-power consumption and high-density electronic devices.

Superior probabilistic computing using operationally stable probabilistic-bit constructed by manganite nanowire

Abstract Probabilistic computing has emerged as a viable approach to treat optimization problems. To achieve superior computing performance, the key aspect during computation is massive sampling and tuning on the probability states of each probabilistic bit (p-bit), demanding its high stability under extensive operations. Here, we demonstrate a p-bit constructed by manganite nanowire that shows exceptionally high stability. The p-bit contains an electronic domain that fluctuates between metallic (low resistance) and insulating (high resistance) states near its transition temperature. The probability for the two states can be directly controlled by nano-ampere electrical current. Under extensive operations, the standard error of its probability values is less than 1.3%. Simulations show that our operationally stable p-bit plays the key role to achieve correct inference in Bayesian network by strongly suppressing the relative error, displaying the potential for superior computing performance. Our p-bit also serves as high quality random number generator without extra data-processing, beneficial for cryptographic applications.

Resistive random access memory based on organic-metallic hybrid polymer

Abstract Resistive random access memories (ReRAMs) based on an organic-metallic hybrid polymer, Poly(Fe-btpyb) Purple, were fabricated. This material was synthesized by complexation of metal ion and organic ligand. When applying forward bias, an abrupt resistance change from a low resistance state (LRS) to a high resistance state (HRS), which is known as reset process, was observed. In contrast, a reverse bias switched the resistance from HRS to LRS (set process). The resistive switching phenomenon is probably caused by the electrochemical oxidation-reduction reaction of the metal ion (Fe(II)/Fe(III)). The nonvolatile memory characteristics were measured with data-retention tests, showing no significant degradation over 105 s. The endurance characteristics exhibited sufficient long-term durability, due to no conformational change of the organic ligand. It is proposed that the difference in charge-transfer efficiency between the reduced state (Fe(II)) and oxidized state (Fe(III)) might be the physical mechanism of the resistive switching.

Bioactive Ion-Confined Ultracapacitive Memristors with Neuromorphic Functions.

The field of bioinspired iontronics, bridging electronic devices and ionic systems, has multiple biological applications. Carbon-based ultracapacitive devices hold promise for controlling bioactive ions via electric double layers due to their high-surface-area and biocompatible porous carbon electrodes. However, the interplay between complex bioactive ions and porous carbons remains unclear due to the variety of structures of bioactive ions present in biological systems. Herein, we investigate the adsorption behavior of a series of bioactive ammonium-based cations with varying alkyl chain lengths in nanoporous carbons. We find that strong physisorption results from the synergistic hydrophobic interaction and electrostatic attraction between porous carbons (with a negative zeta potential) and bioactive cations. Bioactive cations with varying alkyl chain lengths can be irreversibly physically adsorbed and confined within nanoporous carbons resulting in anion enrichment and depletion during electric polarization. This situation, in turn, results in a characteristic memristive behavior in all-carbon capacitive ionic memristor devices. Our findings highlight the relationship between the resistance state of the memristor and ion adsorption mechanisms in all-carbon capacitive devices, which hold potential for future transmitter delivery, biointerfacing, and neuromorphic devices.