Switching Mechanism Research Articles

Van der Waals Epitaxial Growth of One-Unit-Cell-Thick Ferroelectric CuCrS2 Nanosheets.

Ferroelectric two-dimensional (2D) materials with a high transition temperature are highly desirable for new physics and next-generation memory electronics. However, the long-range polar order of ferroelectrics will barely persist when the thickness reaches the nanoscale. In this work, we synthesized 2D CuCrS2 nanosheets with thicknesses down to one unit cell via van der Waals epitaxy in a chemical vapor deposition system. A combination of transmission electron microscopy, second-harmonic generation, and Raman spectroscopy measurements confirms the R3m space group and noncentrosymmetric structure. Switchable ferroelectric domains and obvious ferroelectric hysteresis loops were created and visualized by piezoresponse force microscopy. Theoretical calculation helps us understand the mechanism of ferroelectric switching in CuCrS2 nanosheets. Finally, we fabricated a ferroelectric memory device that achieves an on/off ratio of ∼102 and remains stable after 2000 s, indicating its applicability in novel nanoelectronics. Overall, 2D CuCrS2 nanosheets exhibit excellent ferroelectric properties at the nanoscale, showing great promise for next-generation devices.

Global Stabilization of Antipodal Points on $n$-Sphere With Application to Attitude Tracking

Existing approaches to robust global asymptotic stabilization of a pair of antipodal points on unit $n$-sphere $\mathbb{S}^n$ typically involve the non-centrally synergistic hybrid controllers for attitude tracking on unit quaternion space. However, when switching faults occur due to parameter errors, the non-centrally synergistic property can lead to the unwinding problem or in some cases, destabilize the desired set. In this work, a hybrid controller is first proposed based on a novel centrally synergistic family of potential functions on $\mathbb{S}^n$, which is generated from a basic potential function through angular warping. The synergistic parameter can be explicitly expressed if the warping angle has a positive lower bound at the undesired critical points of the family. Next, the proposed approach induces a new quaternion-based controller for global attitude tracking. It has three advantageous features over existing synergistic designs: 1) it is consistent, i.e., free from the ambiguity of unit quaternion representation; 2) it is switching-fault-tolerant, i.e., the desired closed-loop equilibria remain asymptotically stable even when the switching mechanism does not work; 3) it relaxes the assumption on the parameter of the basic potential function in literature. Comprehensive simulation confirms the high robustness of the proposed centrally synergistic approach compared with existing non-centrally synergistic approaches.

Light-Mediated Multilevel Flexible High-Efficiency Perovskite Resistive Switching Memory Based on Mn:CsPbCl3 Nanocrystals.

Herein, the electrical characteristics, photoelectric properties, resistive switching (RS) mechanism, and flexible storage application of Ag/PMMA&Mn:CsPbCl3/ITO (PMMA = poly(methyl methacrylate)) devices are studied by using the photoelectric material Mn:CsPbCl3 nanocrystals (NCs) embedded in PMMA as the RS layer. The devices exhibit bipolar RS behavior with low operating voltage, excellent cycling endurance (>1000 times), long retention time (≥104 s), high ON/OFF ratio (≈104), and good environmental stability. The flexible memory devices have demonstrated reliable mechanical stability of consecutive 1000 bending cycles. In addition, multilevel data storage is realized by introducing the UV light, and the adjustive resistive switching characteristics is achieved through photoelectric synergistic work. The resistive switching mechanism under the excitation of light has been studied comprehensively. This work may pave a new way for developing the next generation of high-density data storage and photoelectric memristor.

Исследование предиктивных схем управления функционированием организационно-технических систем

Organizational and technical systems are the most common tool for solving national economic problems. However, due to the personnel included in them, they are characterized by stochastic behavior, which raises the issue of developing their probabilistic model. On the other hand, the probabilistic apparatus is a tool for forecasting future phenomena and situations and therefore a mechanism for its use in predictive (forecast) management is needed. For this purpose, the work uses the first probabilistic approximation in the form of a Markov process and its description by the Fokker–Planck–Kolmogorov equation. The purpose of the study is to formulate and solve optimal control problems with probabilistic control quality criteria for a tracking predictive control scheme, as well as to develop a mechanism for metasystem switching of mo¬dels in the case of an adaptive scheme with a predictive model in the control loop. Materials and methods. Based on the analysis of scientific ideas and methodological approaches in predictive management of domestic and foreign authors, as well as mathematical methods and models, two schemes for implementing predictive management were selected to improve the efficiency of the functioning of organizational and technical systems: tracking schemes and adaptive management. Results. The optimal control problem was solved using two methods: Pontryagin's maximum principle and Bellman's principle of dynamic programming. It is shown that in the first case there is a convex upward strategy for achieving the target value of the controlled value with a maximizing approach, and in the second case the result is a convex downward strategy used for the optimal consumption of management resources. In addition, for another predictive control scheme – adaptive with a predictive model in the loop, the effectiveness of using the strategy of metasystem switching of models with the formulation and solution of six metasystem problems has been proven. Conclusion. The proposed approach can be used when designing management systems in organizational and technical systems and choosing behavior strategies in difficult market conditions when solving problems of their development.

3D-Printed Porous Supramolecular Sorbents for Cobalt Recycling.

Electronic waste recycling is a recognized global challenge that requires new strategies to bind and release critical materials selectively, such as cobalt present in lithium-ion batteries. To address this challenge, hierarchical 3D-printed porous polymer scaffolds bearing supramolecular receptors were prepared using vat photopolymerization and their cobalt binding profiles were examined as a function of matrix polarity. By combining high-resolution digital light processing (DLP) with polymerization-induced phase separation (PIPS), functional acrylic copolymer networks with micrometer-level precision of geometry and nanometer-level pores were generated. Covalent integration of a methacrylate-functionalized bisdicyclohexyl acetamide (BDCA-MA) receptor enabled binding and release of cobalt(II) chloride (CoCl2) via a solvent polarity switch mechanism involving a change in solvent from ethanol to water. The present structures proved reusable as shown by sustained high binding efficiency over five bind and release cycles. This platform represents a "green" and energy conscious method for future electronic waste recycling.

Cognitive and neural mechanisms of voluntary versus forced language switching in Chinese-English bilinguals: an fMRI study.

The ecological validity of bilingual code-switching has garnered increasing attention in recent years. Contrary to traditional studies that have focused on forced language switching, emerging theories posit that voluntary switching may not incur such a cost. To test these claims and understand differences between forced and voluntary switching, the present study conducted a systematic comparison through both behavioral and neural perspectives. Utilizing fMRI alongside picture-naming tasks, our findings diverge from prior work. Voluntary language switching not only demonstrated switching costs at the behavioral level but also significantly activated brain regions associated with inhibitory control. Direct comparisons of voluntary and forced language switching revealed no significant behavioral differences in switching costs, and both shared several common brain regions that were activated. On the other hand, a nuanced difference between the two types of language switching was revealed by whole-brain analysis: voluntary switching engaged fewer language control regions than forced switching. These findings offer a comprehensive view of the neural and behavioral dynamics involved in bilingual language switching, challenging prior claims that voluntary switching imposes no behavioral or neural costs, and thus providing behavioral and neuroimaging evidence for the involvement of inhibitory control in voluntary language switching.

Huge mobility difference between the neutral and charged steps on 180° domain walls of PbTiO3 by first-principles calculations

The microscopic mechanism of ferroelectric switching is the motion of domain walls, which is actually accomplished by the movement of tiny steps on the domain walls. Using first-principles calculations, the detailed polarization structures and the motion barriers of neutral and charged steps on 180° domain walls of prototypical ferroelectrics PbTiO3 are elaborately revealed in this study. While the Bloch components get weakened near all neutral steps, they become weakened/strengthened near the head-to-head/tail-to-tail charged steps. The neutral step possesses a lower formation energy but a higher migration barrier, indicating that the charged step could move faster. Based on these results, the possible motion picture of steps on one 180° domain wall of tetragonal ferroelectrics is proposed, which provides a better understanding of the mechanism of domain wall motion and may shed light on the future development of domain wall–based functional devices.

Electrical 180° switching of Néel vector in spin-splitting antiferromagnet.

Antiferromagnetic spintronics have attracted wide attention due to its great potential in constructing ultradense and ultrafast antiferromagnetic memory that suits modern high-performance information technology. The electrical 180° switching of Néel vector is a long-term goal for developing electrical-controllable antiferromagnetic memory with opposite Néel vectors as binary "0" and "1." However, the state-of-art antiferromagnetic switching mechanisms have long been limited for 90° or 120° switching of Néel vector, which unavoidably require multiple writing channels that contradict ultradense integration. Here, we propose a deterministic switching mechanism based on spin-orbit torque with asymmetric energy barrier and experimentally achieve electrical 180° switching of spin-splitting antiferromagnet Mn5Si3. Such a 180° switching is read out by the Néel vector-induced anomalous Hall effect. On the basis of our writing and readout methods, we fabricate an antiferromagnet device with electrical-controllable high- and low-resistance states that accomplishes robust write and read cycles. Besides fundamental advance, our work promotes practical spin-splitting antiferromagnetic devices based on spin-splitting antiferromagnet.

What Happens to a Pyrrole Hemithioindigo Photoswitch Trapped in a Fluorescent Protein?

Artificial molecular photoswitches that can be reversibly controlled into different configurations by external light stimulation have broad application prospects in various fields, such as materials and chemical biology. Among them, the pyrrole hemithioindigo (PHT) photoswitch has a geometric structure similar to that of the fluorescent protein chromophore. What happens when the chromophore is replaced by PHT, and does it achieve similar functions to the original one? To answer these questions, we carried out ONIOM(QM/MM) and classical molecular dynamics studies on the photoisomerization mechanism and spectroscopic properties of PHT in the fluorescent protein. The results showed that in the protein environment, the fate of excited PHT is governed by the competition between fluorescence emission and hula-twist isomerization. Due to the strong steric hindrance effects caused by the interlacing residues in the protein that restrict the PHT conformation transformation, the cis-to-trans isomerization process of PHT needs to overcome a barrier of at least 4.9 kcal/mol; thus, fluorescence emission is more dominant in competition. It is also found that the intermolecular interaction between LYS67 and the carbonyl oxygen of PHT has a significant effect on the fluorescence emission. These results revealed the photochemical reaction mechanism of a light-driven molecular switch in the fluorescent protein and provided further theoretical support for the field of chemical biology.

Ceramic Bowl‐Supported Nanofibrous Membrane with Fluorinated Silsesquioxane‐inspired Switchable Surfaces for Successive Crude Oil/Water Separation and Secondary Water Treatment

A simple, facile and economic approach was developed to transform a 2-tier hydrophilic biased electrospun hybrid PEBAX-FPOSS or Cabon/silica-FPOSS deposited on top of silica aerogel-exfoliated kaolinite ceramic, into hydrophobicity via a wetting switching mechanism subject to %FPOSS variance. Under the same wetting switching mechanism, we did transform originally hydrophobic expanded polystyrene (EP)-FPOSS into super-hydrophobicity with overriding good oil sorption and recovery capacity. Within 5%−10% FPOSS incorporation into PEBAX or Carbon/Silica, the consolidated hybrid membrane scaffold exhibited hydrophilic wettings with the capability not only to separate crude oil/water mixture but also to remove bacteria from both oil/water and polluted water. However, with 30–70% FPOSS blends via electrospinning, the system switched into hydrophobic/oleophilic wetting with the capability to separate crude oil/water in good performance. The hydrophilic electrospun hybrid membranes exhibited good performances in terms of water flux rate, organic rejection, and mechanical strength, which however is an index of %FPOSS incorporation. However, it became impossible to engage in gravity-driven filtration as FPOSS incorporation exceeded 70%.

Rational Design of 2D Supramolecular Networks Switchable by External Electric Fields.

The reversible formation of hydrogen bonds is a ubiquitous mechanism for controlling molecular assembly in biological systems. However, achieving predictable reversibility in artificial two-dimensional (2D) materials remains a significant challenge. Here, we use an external electric field (EEF) at the solid/liquid interface to trigger the switching of H-bond-linked 2D networks using a scanning tunneling microscope. Assisted by density functional theory and molecular dynamics simulations, we systematically vary the molecule-to-molecule interactions, i.e., the hydrogen-bonding strength, as well as the molecule-to-substrate interactions to analyze the EEF switching effect. By tuning the building block's hydrogen-bonding ability (carboxylic acids vs aldehydes) and substrate nature and charge (graphite, graphene/Cu, graphene/SiO2), we induce or freeze the switching properties and control the final polymorphic output in the 2D network. Our results indicate that the switching ability is not inherent to any particular building block but instead relies on a synergistic combination of the relative adsorbate/adsorbate and absorbate/substrate energetic contributions under surface polarization. Furthermore, we describe the dynamics of the switching mechanism based on the rotation of carboxylic groups and proton exchange, which generate the polarizable species that are influenced by the EEF. This work provides insights into the design and control of reversible molecular assembly in 2D materials, with potential applications in a wide range of fields, including sensors and electronics.

Photovoltaic hotspots: A mitigation technique and its thermal cycle

In the rapidly evolving field of solar energy, Photovoltaic (PV) manufacturers are constantly challenged by the degradation of PV modules due to localized overheating, commonly known as hotspots. This issue not only reduce the efficiency of solar panels but, in severe cases, can lead to irreversible damage, malfunctioning, and even fire hazards. Addressing this critical challenge, our research introduces an innovative electronic device designed to effectively mitigate PV hotspots. This pioneering solution consists of a novel combination of a current comparator and a current mirror circuit. These components are uniquely integrated with an automatic switching mechanism, notably eliminating the need for traditional bypass diodes. We rigorously tested and validated this device on PV modules exhibiting both adjacent and non-adjacent hotspots. Our findings are groundbreaking: the hotspot temperatures were significantly reduced from a dangerous 55 °C to a safer 35 °C. Moreover, this intervention remarkably enhanced the output power of the modules by up to 5.3%. This research not only contributes a practical solution to a longstanding problem in solar panel efficiency but also opens new pathways for enhancing the safety and longevity of solar PV systems.

Self-Assembly of Delta-Formamidinium Lead Iodide Nanoparticles to Nanorods: Study of Memristor Properties and Resistive Switching Mechanism.

In the quest for advanced memristor technologies, this study introduces the synthesis of delta-formamidinium lead iodide (δ-FAPbI3) nanoparticles (NPs) and their self-assembly into nanorods (NRs). The formation of these NRs is facilitated by iodide vacancies, promoting the fusion of individual NPs at higher concentrations. Notably, these NRs exhibit robust stability under ambient conditions, a distinctive advantage attributed to the presence of capping ligands and a crystal lattice structured around face-sharing octahedra. When employed as the active layer in resistive random-access memory devices, these NRs demonstrate exceptional bipolar switching properties. A remarkable on/off ratio (105) is achieved, surpassing the performances of previously reported low-dimensional perovskite derivatives and α-FAPbI3 NP-based devices. This enhanced performance is attributed to the low off-state current owing to the reduced number of halide vacancies, intrinsic low dimensionality, and the parallel alignment of NRs on the FTO substrate. This study not only provides significant insights into the development of superior materials for memristor applications but also opens new avenues for exploring low-dimensional perovskite derivatives in advanced electronic devices.

COOLAIR and PRC2 function in parallel to silence FLC during vernalization

Noncoding transcription induces chromatin changes that can mediate environmental responsiveness, but the causes and consequences of these mechanisms are still unclear. Here, we investigate how antisense transcription (termed COOLAIR) interfaces with Polycomb Repressive Complex 2 (PRC2) silencing during winter-induced epigenetic regulation of Arabidopsis FLOWERING LOCUS C (FLC). We use genetic and chromatin analyses on lines ineffective or hyperactive for the antisense pathway in combination with computational modeling to define the mechanisms underlying FLC repression. Our results show that FLC is silenced through pathways that function with different dynamics: a COOLAIR transcription-mediated pathway capable of fast response and in parallel a slow PRC2 switching mechanism that maintains each allele in an epigenetically silenced state. Components of both the COOLAIR and PRC2 pathways are regulated by a common transcriptional regulator (NTL8), which accumulates by reduced dilution due to slow growth at low temperature. The parallel activities of the regulatory steps, and their control by temperature-dependent growth dynamics, create a flexible system for registering widely fluctuating natural temperature conditions that change year on year, and yet ensure robust epigenetic silencing of FLC.

Reliable Memristive Switching Empowered by Ag/NiO/W ReRAM Configuration for Multi‐Level Non‐Volatile Memory Applications

AbstractResistive random‐access memories (ReRAM) are promising candidates for next‐generation non‐volatile memory, logic components, and bioinspired neuromorphic computing applications. The analog resistive switching (RS) tuning with a sizable memory window is crucial for realizing multi‐level storage devices. This work demonstrates the multi‐level storage capability of fabricated Ag/NiO/W ReRAM architecture, controlled through voltage modulations. The fabricated ReRAM structures exhibit stable bipolar analog RS, non‐overlapping resistance, and endurance of ≈104 cycles, respectively, with marginal statistical variations/fluctuations. Also, the fabricated ReRAM offers highly controlled and stable retention characteristics tested up to ≈104 s with significantly controlled statistical variations/fluctuations. Adjacent thereto, it offers a substantially lower operating SET and RESET voltage of 1 and −1 V, respectively. Moreover, the non‐overlapping multiple resistive states are observed with the voltage pulse modulation schemes. Furthermore, the current switching mechanism is described using a model proposed for the conductive filament growth and the contribution of the NiO/W interface layer (IL) toward notable RS of fabricated Ag/NiO/W structures.

Switchable deep eutectic solvent as green and efficient media for liquid-phase microextraction of phenoxyacetic acid herbicides in water and food matrices

In this work, a switchable deep eutectic solvent (SDES) based on fatty acid and polyetheramine ion pair was prepared for liquid-phase microextraction (LPME) of phenoxyacetic acid herbicides in drinking water, beverage and honey matrices. The as-synthesized SDES equipped with an interesting characteristic of fast and reversible polarity switching, achieving homogeneous extraction and rapid bi-phase separation simultaneously. Several key parameters affecting the extraction performance were investigated comprehensively by Box-Behnken design. Under the optimal conditions, the method exhibited excellent linearity (15–4000 μg L−1), low detection limits (3–5 μg L−1), desirable precision (RSD < 8.1 %), and satisfactory recovery (72.6–98.7 %). More importantly, the introduction of SDES can simplify the pre-treatment procedure, shorten extraction time (4 min), and avoid the usage of traditional organic solvent during the whole extraction process. In addition, the switching mechanism of SDES was characterized by FT-IR and 1H NMR, and the forming mechanism of SDES was investigated using density-functional theory. The green of the method was estimated using the analytical ecological scale, the analytical green calculator, and the green analytical procedure index. The cytotoxicity of SDES was investigated and the result displayed that toxicity of the SDES was very low with the EC50 > 500 mg/L. Therefore, the proposed method was green and efficient and revealed considerable application prospects for the extraction of trace analytes from complex materials.

Mechanisms of Electrical Switching of Ultrathin CoO/Pt Bilayers.

We study current-induced switching of the Néel vector in CoO/Pt bilayers to understand the underlying antiferromagnetic switching mechanism. Surprisingly, we find that for ultrathin CoO/Pt bilayers electrical pulses along the same path can lead to an increase or decrease of the spin Hall magnetoresistance signal, depending on the current density of the pulse. By comparing these results to XMLD-PEEM imaging of the antiferromagnetic domain structure before and after the application of current pulses, we reveal the details of the reorientation of the Néel vector in ultrathin CoO(4 nm). This allows us to understand how opposite resistance changes can result from a thermomagnetoelastic switching mechanism. Importantly, our spatially resolved imaging shows that regions where the current pulses are applied and regions further away exhibit different switched spin structures, which can be explained by a spin-orbit torque-based switching mechanism that can dominate in very thin films.

Reversible Switching Based on Truly Intramolecular Long-Range Proton Transfer─Turning the Theoretical Concept into Experimental Reality.

Herein, we demonstrate a working prototype of a conjugated proton crane, a reversible tautomeric switching molecule in which truly intramolecular long-range proton transfer occurs in solution at room temperature. The system consists of a benzothiazole rotor attached to a 7-hydroxy quinoline stator. According to the experimental and theoretical results, the OH proton is delivered under irradiation to the quinolyl nitrogen atom through a series of consecutive proton transfer and twisting steps. The use of a rigid rotor prevents undesired side processes that decrease the switching performance in previously described proton cranes and provides an unprecedented switching efficiency and fatigue resistance. The newly designed system confirms the theoretical concept for the application of proton transfer-initiated intramolecular twisting as the switching mechanism, developed more than 10 years ago, and provides unique insights for the further development of tautomeric molecular switches and motors, molecular logic gates, and new molecular-level energy storage systems.

Enhanced performance of conjugated polymer-based ternary memory devices by embedding Pt nanoparticles

Organic ternary memory devices show higher data storage density than common inorganic binary memory, however, facing the challenge of the low ON/OFF current ratio and high threshold voltage hinders their application. Herein, a conjugated polymer, poly[2,7-(9,9-dioctyl)-fluorene-alt-12 H-benz[5,6]-isoindole[2,1-a] benzimidazole-12-one] (PFBIM), was synthesized and applied to fabricate memristors by spin coating. The PFBIM-based memristors showed unique ternary memory behavior, but their ON/OFF ratio is just 9.6 × 103 and the threshold voltage is − 1.35 V. To improve memory performance, the strategy of polymer film blends Pt NPs was implemented. Impressively, enhanced performance was achieved when the PFBIM-based memristor incorporated 5% Pt NPs, the ON/OFF ratio increased to 1.37 × 105 and the threshold voltage decreased to − 0.65 V. The ternary switching mechanism and the role of Pt NPs on enhanced memristor performance were studied. This work may provide useful information to ameliorate performance and promote the further advance of ternary memory devices.

Realization of future neuro-biological architecture in power efficient memristors of Fe3O4/WS2 hybrid nanocomposites

The future generation of digital technology will heavily rely on power efficient non-volatile resistive memory systems as a potential alternative to flash memory due to its limitations in scalability and endurance. To attain the commercial benchmark, memristors have still lacked performance. This study reports a novel and cost-effective solution processable method for growing surface-modified hybrid nanocomposites (Nc) on a large scale, as an active layer. The solution-processed synthesis approach used for Ag/Fe50W50/Pt hybrid nanocomposite memristor device results in the formation of heterophase grain boundaries, which create residual filaments along these boundaries. The device Fe3O4-WS2(Nc) shows excellent performance, having ultra-low energy consumption (0.1fJ), high reproducibility (10 devices), scalability, excellent endurance (106), and excellent environment stability. Density functional theory (DFT) simulations reveal that structural symmetry distortion and interfacial interaction of hybrid nanocomposite at the interface plays a vital role in the switching mechanism. As high-performance electronic synapses, the optimal pulse scheme enables a steady interaction of short- and long-term plasticity principles, such as spike -time dependent plasticity (STDP) and pulse pair facilitation (PPF), essential for learning and neuromorphic computing analogous to human brain. Moreover, by using Modified National Institute of Standards and Technology (MINST), the memristor device attained a high learning accuracy of 95.4% under convolution neural network (CNN) simulations. The present study revealed that the performance of hybrid-nanocomposite memristors could lead to efficient future neuromorphic architecture.