Small Operating Voltage Research Articles

Reconfigurable Sensing‐Memory‐Processing and Logical Integration Within 2D Ferroelectric Optoelectronic Transistor for CMOS‐Compatible Bionic Vision

AbstractNeuromorphic ferroelectric transistors integrating sensing and memory capabilities for photoelectric stimuli have provided a remarkable platform for multifunctional bionic vision. However, most hardware demonstrations utilizing ferroelectric transistors cannot implement multiple bio‐visual functions simultaneously under a small operating voltage with scalable material systems, which reduces the compatibility with complementary metal‐oxide‐semiconductor (CMOS) technology and blocks further bio‐visual applications. Herein, an optoelectronic transistor gated is constructed with ferroelectric LiNbO3, which exhibits sensing‐memory‐processing functions and logic integration simultaneously under a low operating voltage (≈1.5 V). Benefiting from the programmable photoinduction and strong ferroelectric polarization, the reliable and highly controllable synaptic characteristics and the bio‐visual selective learning behavior are successfully demonstrated. A high recognition accuracy (≈94.5%) in simulations is also achieved due to the unique linear synaptic plasticity. Furthermore, based on dual‐wavelength modulation, the full‐optical logics “AND” and “OR” are established within the same device. This work provides novel opportunities for the complex multifunctional bionic vision and toward large‐scale integration compatible with silicon‐based CMOS processes.

Achieving Reliable and Ultrafast Memristors via Artificial Filaments in Silk Fibroin.

The practical implementation of memristors in neuromorphic computing and biomimetic sensing suffers from unexpected temporal and spatial variations due to the stochastic formation and rupture of conductive filaments (CFs). Here, the biocompatible silk fibroin (SF) is patterned with an on-demand nanocone array by using thermal scanning probe lithography (t-SPL) to guide and confine the growth of CFs in the silver/SF/gold (Ag/SF/Au) memristor. Benefiting from the high fabrication controllability, cycle-to-cycle (temporal) standard deviation of the set voltage for the structured memristor is significantly reduced by ≈95.5% (from 1.535 to 0.0686 V) and the device-to-device (spatial) standard deviation is also reduced to 0.0648 V. Besides, the statistical relationship between the structural nanocone design and the resultant performance is confirmed, optimizing at the small operation voltage (≈0.5 V) and current (100 nA), ultrafast switching speed (sub-100 ns), large on/off ratio (104 ), and the smallest switching slope (SS < 0.01 mV dec-1 ). Finally, the short-term plasticity and leaky integrated-and-fire behavior are emulated, and a reliable thermal nociceptor system is demonstrated for practical neuromorphic applications.

Ultrathin Co0.5NiS Nanosheets for Hydrazine Oxidation Assisted Nitrite Reduction

AbstractNitrite (NO2−) and hydrazine (N2H4) are common N‐pollutants in groundwater. The electrochemical method can realize the treatment of N‐pollutants and the synthesis of energy substance ammonia (NH3). Designing and synthesizing efficient electrocatalysts is of great significance. Herein, ultrathin Co0.5NiS nanosheets attached on nickel foam (Co0.5NiS‐NSs/NF) are synthesized via cyanogel‐NaBH4 hydrolysis process and succedent sulfurization approach. Owing to the ultrathin nanosheet structure and the interaction between Ni and Co, Co0.5NiS‐NSs/NF exhibits high activity for NO2− reduction reaction (NO2−RR), in which the Faraday efficiency is 92.2% and the NH3 yield is 0.25 mmol h−1 cm−2 at −0.15 V potential. Meanwhile, Co0.5NiS‐NSs/NF also displays remarkable activity for N2H4 oxidation reaction in KOH electrolyte. Therefore, a symmetrical Co0.5NiS‐NSs/NF||Co0.5NiS‐NSs/NF electrolyzer is assembled, which only needs the operating voltage of 0.36 V to reach 10 mA cm−2 for NO2−‐to‐NH3 conversion in the presence of N2H4. This work reports a promising and efficient strategy for NH3 production at a small operating voltage and treatment of the N‐pollutants.

Derivation of Ultra-High Gain Hybrid Converter Families for HASEL Actuators Used in Soft Mobile Robots.

This work proposes, analyzes, designs, and validates superior topologies of UHGH converters that are capable of supporting extremely large conversion ratios up to ∼2000× and output voltage up to ∼4-12 kV for future mobile soft robots from an input voltage as low as the range of a 1-cell battery pack. Thus, the converter makes soft robots standalone systems that can be untethered and mobile. The extremely large voltage gain is enabled by a unique hybrid combination of a high-gain switched magnetic element (HGSME) and a capacitor-based voltage multiplier rectifier (CVMR) that, together, achieve small overall size, efficient operation, and output voltage regulation and shaping with simple duty-cycle modulation. With superior performance, power density, and compact size, the UHGH converters prove to be a promising candidate for future untethered soft robots.

Reliable Memristor Crossbar Array Based on 2D Layered Nickel Phosphorus Trisulfide for Energy-Efficient Neuromorphic Hardware.

Designing reliable and energy-efficient memristors for artificial synaptic arrays in neuromorphic computing beyond von Neumann architecture remains a challenge. Here, memristors based on emerging layered nickel phosphorus trisulfide (NiPS3 ) are reported that exhibit several favorable characteristics, including uniform bipolar nonvolatile switching with small operating voltage (<1V), fast switching speed (< 20ns), high On/Off ratio (>102 ), and the ability to achieve programmable multilevel resistance states. Through direct experimental evidence using transmission electron microscopy and energy dispersive X-ray spectroscopy, it is revealed that the resistive switching mechanism in the Ti/NiPS3 /Au device is related to the formation and dissolution of Ti conductive filaments. Intriguingly, further investigation into the microstructural and chemical properties of NiPS3 suggests that the penetration of Ti ions is accompanied by the drift of phosphorus-sulfur ions, leading to induced P/S vacancies that facilitate the formation of conductive filaments. Furthermore, it is demonstrated that the memristor, when operating in quasi-reset mode, effectively emulates long-term synaptic weight plasticity. By utilizing a crossbar array, multipattern memorization and multiply-and-accumulate (MAC) operations are successfully implemented. Moreover, owing to the highly linear and symmetric multiple conductance states, a high pattern recognition accuracy of ≈96.4% is demonstrated in artificial neural network simulation for neuromorphic systems.

Triphasic Ni2P−Fe2P−CoP heterostructure interfaces for efficient overall water splitting powered by solar energy

In this study, we design a triphasic Ni2P − Fe2P − CoP heterostructure appearing under the form of a hierarchical 3D core–shell hybrid (CoP@Ni2P − Fe2P) for bifunctionally catalyzing both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline medium. Density functional theory results indicate that the rich interfaces of Ni2P − Fe2P − CoP architecture exhibit the best electronic properties and enhanced multiple electroactive site number with optimum hydrogen adsorption energy, significantly surpassing the CoP, CoP−Ni2P, or CoP−Fe2P cases. Therefore, the electrolyzer cell of CoP@Ni2P − Fe2P(+,−) requires a small operating voltage of 1.51 V to reach 10 mA cm−2 during alkaline water splitting, outperforming the commercial catalyst couple of Pt/C(−)//RuO2(+) and numerous earlier reports. In addition, the solar-driven water splitting system demonstrates a high solar-to-hydrogen (STH) conversion of 15.33 %, along with excellent long-term stability. The results open a potential approach to design innovative high-performance electrocatalysts for practical green hydrogen production via electrochemical water splitting process.

All-Water-Driven High-k HfO2 Gate Dielectrics and Applications in Thin Film Transistors.

In this article, we used a simple, non-toxic, environmentally friendly, water-driven route to fabricate the gate dielectric on the Si substrate and successfully integrate the In2O3/HfO2 thin film transistor (TFT). All the electrical properties of In2O3 based on HfO2 were systematically analyzed. The In2O3/HfO2 device exhibits the best electrical performance at an optimized annealing temperature of 500 °C, including a high µFE of 9 cm2 V-1 s-1, a high ION/IOFF of 105, a low threshold voltage of 1.1 V, and a low sub-threshold of 0.31 V dec-1. Finally, test the stability of the bias under positive bias stress (PBS) and negative bias stress (NBS) with threshold shifts (VTH) of 0.35 and 0.13 V while these optimized properties are achieved at a small operating voltage of 2 V. All experimental results demonstrate the potential application of aqueous solution technology for future low-cost, energy-efficient, large-scale, and high-performance electronics.

Ultrasensitive Ferroelectric Semiconductor Phototransistors for Photon‐Level Detection

AbstractLow‐light‐level photodetections are highly desired in the fields of astronomy and quantum information. However, the existing techniques suffer from high operation voltages and complexity of fabrication, which reduces its compatibility with complementary metal oxide semiconductors (CMOS) based read‐out circuit and prevent the use of imaging. Here, a low‐light‐level phototransistor that employs a photo‐induced ferroelectric reversal mechanism in a ferroelectric semiconductor channel: α‐In2Se3 is demonstrated. It shows a record‐low noise‐equivalent power of 7.9 × 10−22 W Hz−1/2, a record‐high specific detectivity of 6.34 × 1017 Jones, and sensitivity approaching 20 photons in a photon‐counting mode, and fast time response of 260 µs/50 ns in the rise/decay period. It also works as an optoelectronic memory with an on/off ratio of 2.9 × 105, retention of longer than 10 years, and endurance of more than 106 cycles. Due to its high performance, simple architecture, and small operation voltage, the phototransistor provides a feasible platform for new‐generation low‐light‐level image sensors.

Self-supported ZIF-coated Co2P/V3P bifunctional electrocatalyst for high-efficiency water splitting

Exploring high-efficiency dual-functional electrocatalysts to drive electrochemical water splitting is of great importance for advancement of renewable hydrogen energy. Herein, a hierarchical core–shell structure electrocatalyst ZIF-Co2P/V3P is in situ grown on Ni foam (abbreviated as ZIF-Co2P/V3P@NF) by a stepwise method. Firstly, Co, V layered double hydroxides (CoV-LDHs) is grown directly on Ni foam (NF) substrate by solvothermal method. Secondly, CoV-LDHs@NF is transferred into 2-MeIm solution and its surface is coated with a layer of imidazolate zeolite skeleton (ZIF). Finally, ZIF-Co2P/V3P@NF catalyst is obtained by low-temperature phosphorization method. The performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can be adjusted by tuning molar ratio of Co/V, and the optimized ZIF-Co2P/V3P@NF-2 manifests superior performance due to its core–shell structure covered by ZIF skeleton, rich heterogeneous interfaces, as well as the positive synergistic interaction between the Co2P and V3P. The overpotentials are only 57 mV@10 mA cm−2 for HER and 261 mV@10 mA cm−2 for OER. Remarkably, the alkaline electrolyzer assembled with ZIF-Co2P/V3P@NF-2 catalyst acquires a small operating voltage of 1.54 V to drive the current density of 10 mA cm−2 and displays excellent long-term durability. This work provides a novel opinion for design and preparation of non-noble metal electrocatalysts.

Amorphous Boron Nitride Memristive Device for High-Density Memory and Neuromorphic Computing Applications.

Although two-dimensional (2D) nanomaterials are promising candidates for use in memory and synaptic devices owing to their unique physical, chemical, and electrical properties, the process compatibility, synthetic reliability, and cost-effectiveness of 2D materials must be enhanced. In this context, amorphous boron nitride (a-BN) has emerged as a potential material for future 2D nanoelectronics. Therefore, we explored the use of a-BN for multilevel resistive switching (MRS) and synaptic learning applications by fabricating a complementary metal-oxide-semiconductor (CMOS)-compatible Ag/a-BN/Pt memory device. The redox-active Ag and boron vacancies enhance the mixed electrochemical metallization and valence change conduction mechanism. The synthesized a-BN switching layer was characterized using several analyses. The fabricated memory devices exhibited bipolar resistive switching with low set and reset voltages (+0.8 and -2 V, respectively) and a small operating voltage distribution. In addition, the switching voltages of the device were modeled using a time-series analysis, for which the Holt's exponential smoothing technique provided good modeling and prediction results. According to the analytical calculations, the fabricated Ag/a-BN/Pt device was found to be memristive, and its MRS ability was investigated by varying the compliance current. The multilevel states demonstrated a uniform resistance distribution with a high endurance of up to 104 direct current (DC) cycles and memory retention characteristics of over 106 s. Conductive atomic force microscopy was performed to clarify the resistive switching mechanism of the device, and the likely mixed electrochemical metallization and valence change mechanisms involved therein were discussed based on experimental results. The Ag/a-BN/Pt memristive devices mimicked potentiation/depression and spike-timing-dependent plasticity-based Hebbian-learning rules with a high pattern accuracy (90.8%) when implemented in neural network simulations.

Modeling and Understanding the Compact Performance of h‐BN Dual‐Gated ReS2 Transistor

AbstractIn this study, high‐performance few‐layered ReS2 field‐effect transistors (FETs), fabricated with hexagonal boron nitride (h‐BN) as top/bottom dual gate dielectrics, are presented. The performance of h‐BN dual gated ReS2 FET having a trade‐off of performance parameters is optimized using a compact model from analytical choice maps, which consists of three regions with different electrical characteristics. The bottom h‐BN dielectric has almost no defects and provides a physical distance between the traps in the SiO2 and the carriers in the ReS2 channel. Using a compact analyzing model and structural advantages, an excellent and optimized performance is introduced consisting of h‐BN dual‐gated ReS2 with a high mobility of 46.1 cm2 V−1 s−1, a high current on/off ratio of ≈106, a subthreshold swing of 2.7 V dec−1, and a low effective interface trap density (Nt,eff) of 7.85 × 1010 cm−2 eV−1 at a small operating voltage (&lt;3 V). These phenomena are demonstrated through not only a fundamental current–voltage analysis, but also technology computer aided design simulations, time‐dependent current, and low‐frequency noise analysis. In addition, a simple method is introduced to extract the interlayer resistance of ReS2 channel through Y‐function method as a function of constant top gate bias.

Structure optimization of carbon nanotube ionization sensor based on fluid model

Compared with the traditional ionization sensor, triple electrode ionization gas sensor based on carbon nanotubes features excellent performances of small size and low operation voltage, and plays an important role in developing smart grids and the ubiquitous Internet of Things. However, they exhibit the disadvantages of small collecting current and low sensitivity, and need to be optimized in structure. Based on the Townsend discharge mechanism and three governing equations of particle mass conservation, electron energy conservation and Poisson equations, a two-dimensional plasma discharge fluid simulation model of the sensor is established by using the COMSOL Multiphysics software. According to gas composition, component concentration, structure of the sensor and voltage applied to the electrodes, we determine the chemical reaction, reaction rate coefficient, field control equation, initial values and boundary conditions. In order to calculate the interior distribution of charged particles inside the boundary, the inter-electrode space region is meshed. Initial values of mesh are set, such as a dense mesh of nano-meter length around the electrode having micro-nano structure, and a rough mesh of micro-meter length in the other region of inter-electrode space. The initial values of time-step are set for each mesh grid, and the discharge model of each mesh grid is numerically solved by the finite volume method. The three linkage governing equations are discretized and calculated iteratively in time and space, and the mesh values and time-steps are adjusted to make the results converged. The electrostatic field distribution and the average collecting current density of the eight kinds of sensors are obtained in the background gas of nitrogen. The optimal sensor structure is obtained by comparing the electric field intensities and current densities under different structure parameters. The eight kinds of the sensors are prepared for experimentally verifying the optimization method. The optimal structure of the 7# sensor has the highest collecting current density in the eight kind structures, which is consistent with the simulation results, and proves the feasibility of the structure optimization method proposed in the paper. Based on the optimal structure, the sensors, respectively with the electrode spacings of 100 and 120 μm, are fabricated, and the response characteristics of NO/SO&lt;sub&gt;2&lt;/sub&gt; mixture gas are obtained. Compared with other technologies, the sensor with optimal structure exhibits 1－2 orders of sensitivity higher than the others. The optimized triple electrode ionization sensor based on carbon nanotubes exhibits many potential applications.

An Investigation of SEI Layer Composition in Presence of Nano-Fillers in Mcmb Electrodes

Since the advent of first commercial Li-ion battery (LIB) in 1991 by Sony, a continuous improvement in their electrochemical performance has been realized. Research has been focused on developing anode materials having higher energy density and specific capacity to replace the existing graphitic anodes [1]. A number of materials such as SnO2 [2], Li4Ti5O12 [3], Si [4] etc. have been extensively studied. Despite displaying promising initial electrochemical characteristics, the large volume change for most of these materials causes the rupture of the solid electrolyte interface (SEI) layer. This repeated breakage and replenishing process of the SEI layer results in continuous decomposition of electrolyte and loss of cathode Li inventory thereby shortening cycle life. Moreover, some other materials such as TiO2 face the problem of low electronic conductivity, small operating voltage window and high cost [5]. Another approach to improve the long-term performance of LIB anodes, in terms of high rate performance and cycling stability, is to further improve the electrochemical performance of graphitic materials. Graphite experiences a volume change about 10% during intercalation/deintercalation [6, 7]. However, the brittle inorganic film may crack and new SEI will form if the SEI surface film is not mechanically stable to accommodate this volumetric strain. Therefore, it is critically important to build-up a thin, stable and ionically conducting surface layer that can tolerate volume change and offer low impedance to ensure a near reversible cycling performance. In this work, we explore the formation of SEI layer and its chemistry on mesocarbon microbeads (MCMB) electrode in presence of different conducting nano-fillers such as carbon black (CB) and carbon nanotubes (CNT). The SEI is characterized ex-situ using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) providing insight into its composition together with nano-scale morphological description. To carry out the depth analysis of SEI layer, the XPS spectra were recorded after sputtering the samples for a time of 400, 2200, 4000, 5800 and 7600 sec. as shown in Fig.1a. To demonstration the effect of nano-fillers, the C1s spectra for CB as conducting additives exhibits a strong signal between 284-285 eV (C-C), 289-290 eV (Li2CO3 or alkylcarbonate) and between 285-286 eV (alkoxide) on the cycled electrode as shown in Fig. 1. As shown, the proportion of Li2CO3 steadily decreases with sputtering indicating its lower presence in inner layers of the SEI. In case of CB as conductive additives, the insignificant change in proportion of CO3-CO (Fig. 1b) suggests a mechanically weak SEI film formed on the surface. On the other hand, the surface film generated in presence of CNT as additives offers a larger CO3 proportion and significantly reduced CO (Fig. 1b). This suggests the SEI film formed on the surface of MCMB is mechanically strong due to higher proportion of carbonate. Significantly, the ratio of amount of CO3 to CO ratio is shown to lie between 0.7 to 1.5 in case of mixed CB-CNT nano-fillers as conducting additives. This finding indicates that the SEI formed in the presence of mixed nano-fillers offers (a) flexibility to accommodate partial strain generated due to volume change, and (b) is capable of conducting Li-ion as a result of a relatively higher percentage of carbonates. Reference s : [1] F. S. Li, Y. S. Wu, J. Chou, M. Winter and N. L. Wu, Adv. Mater., 27, 130-137 (2015). [2] P. Meduri, C. Pendyala, V. Kumar, G. U. Sumanasekera, and M. K. Sunkara, Nano Lett., 9, 612-616 (2009). [3] M. Wagemaker, D. R. Simon, E. M. Kelder, J. Schoonman, C. Ringpfeil, U. Haake, D. Lützenkirchen-Hecht, R. Frahm, and F. M. Mulder, Adv. Mater., 18, 3169-3173 (2006). [4] X. Chen, K. Gerasopoulos, J. Guo, A. Brown, C. Wang, R. Ghodssi, and J. N. Culver, ACS Nano, 4, 5366-5372 (2010). [5] N. Nitta, F. Wu, J. T. Lee, and G. Yushin, Mater. Today, 18, 252-264 (2015). [6] S. Ahamad, and A. Gupta, Electrochim. Acta, 297, 916-928 (2018). [7] S. Ahamad, M. Ahmad, B. R. Mehta, and A. Gupta, J. Electrochem. Soc. 164, A2967-A2976 (2017). Figure 1

Investigation of Na3V2(PO4)2O2F as a sodium ion battery cathode material: Influences of morphology and voltage window

Na-ion batteries (NIBs) offer a low-cost solution for energy storage applications. However, the cathode materials of NIBs are still limited by their low energy density, exhibiting either small capacity or low operation voltage. In this work we explored a high-voltage cathode material, vanadium fluorophosphate Na3V2(PO4)2O2F. We prepared the material in both nano-size and micro-size by a hydrothermal method, adopting ethylene glycol and water as the solvent, respectively. The morphology and physiochemical properties of the nano-sized and micro-sized Na3V2(PO4)2O2F are systematically characterized and the battery cycling performances are examined in different voltage windows. Interestingly, we find that the battery capacity and rate capability are highly dependent on the cathode morphology while the cyclability of the electrode is mainly affected by the operation voltage window. The nano-sized Na3V2(PO4)2O2F can achieve an energy density of 459 Wh kg−1 with good cyclability within a voltage window of 3–4.5 V while the micro-sized Na3V2(PO4)2O2F delivers a much poorer electrochemical performance due to its coarse morphology. By widening the operation voltage window to 1–4.5 V, an energy density of 660 Wh kg−1 can be obtained from the nano-sized Na3V2(PO4)2O2F electrode at the initial cycles, but it decreases significantly after tens of cycles. We analyzed the rate capability of Na3V2(PO4)2O2F by considering multi Na+ ion intercalation reactions and found the large voltage window induced additional Na+ ion intercalation reaction occurs through a much slower kinetic process as compared to other reactions activated in the narrower voltage window (e.g., 3–4.5 V). The model of the intercalation reactions as well as the possible reasons of the degraded cycling performance in wide operation voltage windows are discussed based on the battery charging-discharging behavior, electrochemical impedance analysis, ex-situ morphology measurements and previously established material models. The findings validate the potential of Na3V2(PO4)2O2F as a high energy density cathode material for NIB, but also call for new crystal structure design of Na3V2(PO4)2O2F to achieve high energy density and good cyclability at the same time.

Eco-friendly, low-temperature solution production of oxide thin films for high-performance transistors via infrared irradiation of chloride precursors

In this paper, we present the infrared (IR) irradiation of chloride precursors as a promising method for the eco-friendly, low-temperature solution fabrication of oxide film devices, which typically require thermal annealing at temperature over 450 °C. By the IR irradiation of AlCl3 precursor, high-quality Al2O3 dielectric films were prepared at a low temperature of 230 °C. The obtained Al2O3 dielectric layers had high dielectric properties, such as a high capacitance of 158 nF/cm2 and a small leakage current of 5.4 × 10−8 A/cm2. Various structure characterizations confirmed the high quality of Al2O3 films produced by IR irradiation. Moreover, full low-temperature solution-produced thin-film transistors (TFTs) were fabricated through the IR irradiation of chloride precursors. The In2O3 TFTs achieved a high mobility of 33.6 cm2V−1s−1 at a small operation voltage of 4 V. Compared with the common thermal annealing method, IR irradiation results in better precursor conversion, higher oxygen lattice, and fewer oxygen defects. These results suggest that IR irradiation can serve as a new approach for the eco-friendly, low-temperature solution production of various oxide thin films and devices. The method is also very promising for the low-energy production of functional materials and devices.

CoNi/Ba0.5Sr0.5Co0.8Fe0.2O3−δ/N-doped-carbon as a highly-active bifunctional electrocatalyst for water splitting

Perovskite-type oxides are considered as promising electrocatalysts to replace noble metals. Their electrochemical water splitting activity is, however, somewhat limited. This work reports a facile approach to promote the water splitting kinetics of a perovskite oxide, Ba0.5Sr0.5Co0.8Fe0.2O3−δ, by constructing a core-shell structured composite, CoNi/Ba0.5Sr0.5Co0.8Fe0.2O3−δ/N-doped-C, which couples Ba0.5Sr0.5Co0.8Fe0.2O3−δ with CoNi nanoparticles and N-doped-C. By this simple approach, the hydrogen evolution reaction inactive Ba0.5Sr0.5Co0.8Fe0.2O3−δ is transformed into a highly efficient catalyst (CoNi/Ba0.5Sr0.5Co0.8Fe0.2O3−δ/N-doped-C), which shows a small overpotential (0.18 V) to achieve a current density of 10 mA cm−2 in 1 M KOH. The CoNi/Ba0.5Sr0.5Co0.8Fe0.2O3−δ/N-doped-C also exhibits a remarkably high activity for oxygen evolution reaction in 1 M KOH solution. A small overpotential of 0.22 mV is demanded to drive a current density of 10 mA cm−2, which is superior to that of pristine Ba0.5Sr0.5Co0.8Fe0.2O3−δ and many state-of-the-art catalysts. An alkaline electrolyzer using CoNi/Ba0.5Sr0.5Co0.8Fe0.2O3−δ/N-doped-C as both electrodes delivers a current density of 10 mA cm−2 at a small operating voltage (1.64 V), much superior to a symmetric prototype using Ba0.5Sr0.5Co0.8Fe0.2O3−δ. Therefore, CoNi/Ba0.5Sr0.5Co0.8Fe0.2O3−δ/N-doped-C is among the best bifunctional catalysts for water splitting. More generally, this work opens new opportunities regarding designs of novel electrocatalysts and further improvements of state-of-the-art catalysts for various applications.

Solution-processed flexible non-volatile resistive switching device based on poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4, 8-diyl)]: polyvinylpyrrolidone composite and its conduction mechanism

Recently, solution-processed resistive switches for wearable electronics have got tremendous attention and are required for different applications due to their easy process and fabrication. Hence, this paper proposes the solution-processed resistive switching memory device based on two polymers, poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4, 8-diyl)] (F8BT) and polyvinylpyrrolidone (PVP) composite, which is fabricated on a flexible indium–tin–oxide (ITO)-coated polyethylene terephthalate (PET) substrate through spin coating technology. The fabricated device demonstrates a perfect non-volatile bipolar resistive switching through small operating voltage sweeping of ± 1.5 V, and its high-resistance state (HRS) and low-resistance state (LRS) are 92678.89 Ω and 337.85 Ω, respectively. To verify the non-volatility and long-term stability, the device is checked for more than 700 endurance cycles. During these cycles, the variations of HRS and LRS are 48 Ω and 37.35 Ω, respectively. The retention time is checked for more than 60 days, and the ROFF/RON ratio is 274.31. The bendability is carried out up to bending diameters < 10 mm, and FESEM is used for the morphological characteristics of the device. Conduction mechanism of the proposed device is supported by space charge-limited conduction (SCLC) which is explained by the log–log I–V slope-fitting curve. The results insure that the F8BT:PVP composite-based resistive switching device is to be a potential candidate for the future flexible and low-power non-volatile resistive switching memory device.

Tunnel-Field-Effect Spin Filter from Two-Dimensional Antiferromagnetic Stanene

We propose a device concept, based on monolayer stanene, able to provide highly polarized spin currents (up to a $98\%$) with voltage-controlled spin polarization operating at room temperature and with small operating voltage ($0.3$ V). The concept exploits the presence of spin-polarized edge states in a stanene nanoribbon. The spin polarization of the total current can be modulated by a differential tuning of the transmission properties, and of the occupation of edge states of different spin, via the application of an in-plane electric field. We demonstrate device operation using ab-initio and quantum transport simulations.

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

Thermal runaway has been a long-standing safety issue impeding the development of high-energy-density batteries. Physical safety designs such as employing circuit-breakers and fuses to batteries are limited by small operating voltage windows and no resumption of original working condition when it is cooled down. Here we report a smart thermoresponsive polymer electrolyte that can be incorporated inside batteries to prevent thermal runaway via a fast and reversible sol-gel transition, and successfully combine this smart electrolyte with a rechargeable Zn/α-MnO2 battery system. At high temperature, battery operation is inhibited as a result of the increased internal resistance caused by the gelation of liquid electrolyte. After cooling down, the electrolyte is spontaneously reversed to sol state and the electrochemical performance of the battery is restored. More importantly, sol-gel transition enables the smart battery to experience different charge-discharge rates under various temperature levels, providing a smart and active strategy to achieve dynamic and reversible self-protection.

Ionic Liquid Gating Control of Spin Reorientation Transition and Switching of Perpendicular Magnetic Anisotropy.

Electric field (E-field) modulation of perpendicular magnetic anisotropy (PMA) switching, in an energy-efficient manner, is of great potential to realize magnetoelectric (ME) memories and other ME devices. Voltage control of the spin-reorientation transition (SRT) that allows the magnetic moment rotating between the out-of-plane and the in-plane direction is thereby crucial. In this work, a remarkable magnetic anisotropy field change up to 1572 Oe is achieved under a small operation voltage of 4 V through ionic liquid (IL) gating control of SRT in Au/[DEME]+ [TFSI]- /Pt/(Co/Pt)2 /Ta capacitor heterostructures at room temperature, corresponding to a large ME coefficient of 378 Oe V-1 . As revealed by both ferromagnetic resonance measurements and magnetic domain evolution observation, the magnetization can be switched stably and reversibly between the out-of-plane and in-plane directions via IL gating. The key mechanism, revealed by the first-principles calculation, is that the IL gating process influences the interfacial spin-orbital coupling as well as net Rashba magnetic field between the Co and Pt layers, resulting in the modulation of the SRT and in-plane/out-of-plane magnetization switching. This work demonstrates a unique IL-gated PMA with large ME tunability and paves a way toward IL gating spintronic/electronic devices such as voltage tunable PMA memories.