Low Switching Voltage Research Articles

Self‐assembled vapor-transport-deposited SnS nanoflake-based memory devices with synaptic learning properties

The most salient features of resistive switching (RS) devices are low energy consumption, fast switching speed, and high-density integration, which render them promising candidates for realizing non-volatile memory and artificial synaptic devices. However, the growth of functional switching layers for RS devices needs innovative deposition techniques. Herein, we utilize a high-throughput vapor-transport-deposition (VTD) technique for synthesizing self-assembled tin-sulfide (SnS) nanoflakes, which are then used as a switching layer to fabricate an RS device. First principle calculations are conducted to understand the optoelectronic properties of SnS by employing density functional theory. The proposed Ag/SnS/Pt memory device exhibits substantial merits, including low-switching voltages (VSET: 0.22 V and VRESET: −0.20 V), suitable ON/OFF ratio (∼259), excellent endurance (106), and extended memory retention (106 s) characteristics. In addition, RS stochasticity is modeled using statistical time-series analysis via Holt’s exponential smoothing. Interestingly, the device can emulate multiple synaptic functionalities, including potentiation, depression, paired-pulse facilitation, paired-pulse depression, excitatory postsynaptic current, inhibitory postsynaptic current, and advanced spike-timing dependent plasticity rules. Moreover, the proposed synaptic device can detect the edge of images by utilizing a convolutional neural network. The unique and efficient VTD-SnS-based device will be a potential candidate for high-density non-volatile memory and neuromorphic computing applications.

Realization of dual-functional resistive switching characteristics in Ag−In−Zn−S/sericin peptide-based memristive device

Employing suitable materials and device engineering is one of the crucial methods toward the realization of multifunctional memristive devices for constructing bioinspired neuromorphic systems. In this work, dual-functional memristors composed of eco-friendly natural silk sericin, coexistently enabling the achievement of threshold switching and memory switching triggered by adjusting the compliance current value, have been fabricated with a specific two-terminal device structure: Ag/Ag−In−Zn−S/silk sericin/W. Experimentally, the as-manufactured memristors exhibit several desirable qualities, such as low switching voltage (< 0.7 V), relatively small cycle-to-cycle and device-to-device variabilities, nonvolatile multilevel storage characteristics, and rapid switching speed (40 ns). Beyond these qualities, fundamental synaptic behaviors, such as paired-pulse facilitation and spike-timing-dependent plasticity (STDP), have been mimicked. This was made possible by a filamentary mechanism based on Ag migration. The fitted time constants corresponding to the STDP potentiation and depression are about 30 ms, and the highest changes in synaptic weight for positive and negative voltage pulses are 84.4% and 61.7%, respectively. Furthermore, the typical coincidence detection task has been executed, demonstrated by simulation based on the fitted STDP's parameters of the sericin-based device. The results from this study indicate that the sericin-based memristors, as designed, have the potential to be employed in the creation of versatile neuromorphic devices for neuromorphic computing systems.

Donor-acceptor hyperbranched copolyimides contain different linear segment for electrochromic and resistive memory devices

In this work, two hyperbranched copolyimides (O-coPI and F-coPI) were synthesized which the diamine donors in the linear segment contain different substituents. To investigate the effects of substituents in donors on their memory behavior, the corresponding linear polyimides (F-LPI and O-LPI) were also discussed. The devices based on hyperbranched copolyimides exhibited non-volatile write once read many times memory (WORM) behavior, while the devices based on linear polyimides exhibited volatile memory dynamic random-access memory (DRAM) behavior. Polyimides (O-coPI and O-LPI) prepared with methoxy-substituted diamine donors have low switching voltages due to their good electron-donating properties. In addition, O-coPI and O-LPI also exhibit electrochromic properties. Hyperbranched copolyimide O-coPI have higher optical contrast and faster response time than that of linear polyimide O-LPI. This work provides a new direction for the development of multifunctional memory materials.

A BMO‐based MRPID controller with optimal control of speed in hybrid stepper motor

AbstractThis paper proposes a Barnacles mating optimizer‐based multi‐resolution proportional‐integral derivative (MRPID) controller for precise speed control of the hybrid stepper motor (HSM). The proposed approach is a barnacle mating optimizer (BMO) control scheme. The main objective of this approach is to use the MRPID controller to improve speed control in particular and uncertain conditions. The BMO is utilized to create the proposed MRPID controller. The proposed converter has a low switching voltage and uses a low input current. The proposed converter supplies a large amount of power to the voltage source inverter (VSI), which converts DC to AC and then supplies it to the HSM. The HSM can be utilized in various settings, including robots and factory applications. Then, the performance of the proposed system has been evaluated in the MATLAB platform and compared with various existing systems. The existing adaptive neuro‐fuzzy inference system (ANFIS) and the moth flame optimization algorithm (MFO) methods are used to validate the efficiency of the proposed controller. The proposed system rise time is 0.0007, the settling time is 0.1, the recovery time is 0.221, the AMU is 1.205, the IAE is 0.1034, and the SSE is 0.234. According to the simulation findings, the suggested system is statistically significant.

Improved Duty Compensation Control-Based Bidirectional Resonant DC−DC Converter With Reduced Input-Current Ripple for Battery Energy Storage Systems

This paper proposes an improved duty control-based resonant bidirectional dc–dc converter (BDC) to remarkably minimize input-current ripple for battery energy storage systems. The proposed converter offers a resonant-boost operation using a pulse-width-modulation (PWM) full-bridge circuit with a push-pull transformer under the forward-mode. Whereas, in the backward-mode, a resonant-buck operation is implemented with a PWM neutral-point-clamped (NPC)-type circuit. Unlike conventional current-fed BDCs, the most appealing characteristic of the proposed converter is the NPC-type structure with a push-pull transformer, which can significantly mitigate the input-current ripple without using extra input-inductors. Moreover, the proposed BDC minimizes the conduction-loss of the low-voltage side bottom switches by alleviating unbalanced DC offset-currents via proposed duty-compensation control under mismatched magnetizing inductances of the transformer's primary-windings. The designed circuit operation is analyzed in detail and its practicability has been fully confirmed with the proportional-integral and spider-monkey-optimization control techniques-based experimental verifications using a prototype 1-kW test-bed.

Hysteresis Resonance and Multi-Pinched Hysteresis Loops in Cu/Cu:ZnO/Cu Resistive Switching Devices

At present, great attention is being devoted towards resistive switching devices owing to lower switching voltage (<3 V), higher tolerance (> 10∧6 cycles), higher scalability (< 10 nm), multi-bit operations, and higher information storage time (10 years) compared to the existing broadly employed transistor technology. This was all possible owing to the accidental discovery of memristance by Hewlett Packard (HP) labs in 2008. In the past few decades, discoveries of such unique electronic properties have led to tremendous technological advancements. Consequently, it is very important to continually seek newer electronic characteristics. In this work, copper (Cu)-doped zinc oxide (ZnO) thin film was synthesized on Cu electrodes to form a Cu/Cu: ZnO/Cu resistive switching device. Function generator and oscilloscope were employed to obtain the electronic characteristics of the device instead of conventional techniques, which resulted in a 96.17% improvement in total equipment expenses. Most importantly, the proposed device exhibited hysteresis resonance and multi-pinched hysteresis; such phenomena have never been reported to date. These characteristics are extremely essential towards futuristic electronics for the development of computational circuits with meliorated performance, electronic systems with improved controllability, memory cells with higher data storage, and in-memory-based processing capabilities.

High gain coupled inductor SEPIC based boost inverter using extended SPWM

This research work designs a high gain coupled inductor SEPIC (CI-SEPIC) based boost inverter. This topology presents low switching voltage stress, high output DC and AC voltage and highly efficient system, which makes it suitable for renewable energy applications. A seventh order system is obtained through dynamic modelling of the CI-SEPIC converter for which PID controller is designed to track the reference value. The extended sine-wave pulse width modulation (ESPWM) has maintained the high gain without compromising the efficiency and ensured low voltage stress on the switching devices. Simulation and experimental results validated that CI-SEPIC based boost inverter with ESPWM achieved high dc gain of 15.98, boost factor of 25, exceptional dc-ac coupling with minimum possible capacitance of 3.3uF, decreased device stress by 33% and smaller size of the complete system.

Insights into nano-mechanical degradation behavior of Ag/Ti2AlC composite under different arc erosion stages

Serious arc erosion is the main reason for premature failure of the Ag-matrix composite electrical contact materials in actual service. Clarifying the structure and property degradation process is crucial for creating eco-friendly Ag/MAX electrical contacts and upgrading high-performance materials for low-voltage switch applications. In this study, the representative Ag/Ti2AlC electrical contacts were designed into three arc erosion stages (from 1 to 5610 cycles) by ex-situ arc discharging experiment, and the nanoindentation technique was then applied to in-depth analyze the evolution behavior of nano-mechanical properties by comparing nano hardness, modulus, creep, continuous stiffness, elastic/plastic deformation, and NanoBlitz 3D Mapping indentation results in different erosion stages. Finally, the inherent relationship among the structural dissociation of Ti2AlC, and compositional changes of Ag/Ti2AlC interface and nano-mechanical properties of composite was revealed, and the material degradation model and anti-arc erosion mechanism were proposed. This work further elucidates the intrinsic source of excellent arc erosion resistance and degradation process of Ag/Ti2AlC composite from the nano-mechanical perspective and lays a theoretical foundation for the future design and optimization of this material system.

Three Phase PFC Converter With Multilevel Inductive Switching Network

The rising power requirement of the on-board charger (OBC) demands high efficiency and high power density in the 3-phase power factor correction (PFC) converters. However, due to the large volume of boost inductors and filters of the conventional 2-level converters, their power density is limited. In this paper, multilevel inductive switching network (MISN) modules based on low-voltage switches are arranged in series at the ac-side to reduce the large size of inductors and filters. Besides, the operating principle and control strategy of the 3-phase MISN-PFC converter are analyzed. In addition, to determine the multiple variables of the MISN module, the design methodology is proposed based on the loss model and volume model for the multilevel converter. Finally, a 10kW prototype has been established to verify the analysis, where 99% efficiency at full load and 430W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density are achieved.

A single phase modified Y-source inverter with high voltage gains and reduced switch stresses

Abstract This study is dedicated to develop a single-phase modified Y-source inverter (m-YSI) topology having a high boost factor and low switch voltage stress by adding a switch to the low voltage region. Thanks to this structure, continuous input current and wide control range are achieved regardless of winding factor. Since an external switch is used in the recommended modified Y-source inverter, the modulation index and duty ratio are controlled independently. Detailed analyses of the modified Y-source inverter were performed using Matlab/Simulink and its performance was compared with conventional Y-source inverters. Compared to selected conventional Y-source inverters, the proposed m-YSI has almost three times less voltage stress. A lower-cost topology has been obtained in which state-of-the-art control methods can be applied, thanks to a wide control range and circuit components with a low power ratio. This proposed model can be used as a double-stage micro-inverter in photovoltaic systems.

Extraction, chemical, and dual-functional memory and threshold resistive switching characteristics of Elaeodendron buchananii extract

This work presents a study on the electrical properties of plant materials, which is a fascinating area of research. These materials show promising potential in mitigating the exponential increase in electronic waste by enabling the development of eco-friendly electronic devices that can biodegrade. This research article showcases findings on the extraction, chemical analysis, and dual-functional memory and threshold resistive switching of extracts from the Elaeodendron buchananii plant. We report threshold switching with impressive ON/OFF ratio of >103, a retention time of ≥103, and endurance of 20 cycles, for the sandwich type device consisting of Elaeodendron buchananii plant extract-based film positioned between silver and indium-doped tin oxide electrodes. After modifying the experimental parameters, specifically by reducing the voltage scan increments to 1mV and increasing the compliance current to 150μA, transition from threshold switching to bipolar memory mode was detected. This particular memory mode exhibited an ON/OFF ratio of 10 and demonstrated very low switching voltages of −0.37V and +0.22V, although for only a limited number of write/erase cycles. The switching mechanism for both the threshold and memory mode can be attributed to the formation of conductive filaments caused by the migration of oxygen vacancies.

A Flat-Top Single-Ended Resonant Converter With Low Switch Voltage Stress

This paper proposes a flat-top single-ended resonant converter (SERC) for wireless charger with the merit of low switch voltage stress, by introducing a parallel LC network in series with the primary switch. A characteristics analysis of the proposed SERC is performed in time domain, obtaining the ZVS condition, power transfer capacity expression and the time requirement to achieve an ideal voltage cancelling. Due to the injected third harmonic, the voltage waveform of the switch can be shaped into a near trapezoid or a saddle shape. From the perspective of waveform superposition, we derive the conditions for the minimum switch voltage stress and the flat-top waveform of switch voltage. Finally, a 1900W prototype is built to verify the theoretical analysis. The experimental results show that the proposed converter achieved a flat-top switch voltage waveform and the voltage stress of 2.12 times the input voltage at full load, compared to that of 2.65 times the input voltage for the conventional one. Besides, the maximum efficiency is also increased to 93.33% from 92.32%.

Electrical and Optical Investigation of an Electric Arc in Hydrogen for short gaps

Hydrogen or mixtures containing hydrogen represent attractive gases for low-voltage switching devices because of increased arc quenching behaviour. However, fundamental electrical properties of arcs in hydrogen are still not well known. In this paper, first results of a study of a DC switching arc in pure hydrogen at 1 bar between graphite electrodes are presented for low currents of 8 and 16 A. The arc voltage and current are measured during contact separation. High-speed images of the arc are processed to determine the arc length considering the high arc dynamics with erratic elongations and jumps of the electrode attachment. The arc voltage dependence on the length results in a typical sheath voltage of approximately 23 V and mean electric fields in the arc column of 18.7 V/mm at 8 A and 10.8 V/mm at 16A.

(Invited) Design and Modeling of Resistive Switching Devices for Neuromorphic Applications

Resistive switching devices are a critical component for the realization of computational systems that mimic biological neural systems. In biological systems, connection weights between the neurons are dependent on the time lapse between the neurons’ action potentials. Resistive switching devices (memristors) with multiple conductance states can mimic this biological spike-time-dependent plasticity (STDP) behaviour, with multiple conductance states being analogous to different synaptic weights. Additionally, memristors are one of the contenders as storage elements in non-volatile memories. The change in conductance in memristors can be broadly attributed to vacancy migration inside the switching layer (valence change memory) or the formation of metallic filaments inside the switching layer (electrochemical metallization).Electrochemical metallization-based memristors with vertical transport and small inter-electrode distances have been reported recently. Their device characteristics exhibit multiple conductance states with relatively low switching voltages, which makes them well-suited for low-power neuromorphic applications. Our work models the transport in these memristors, focusing on explaining and capturing their current-voltage characteristics. Our model also captures the switching dynamics (with an emphasis on estimating switching energies and delays) and explains the experimentally observed STDP behaviour in these devices. We have proposed models for filament growth and dissolution along one dimension (axial) and two dimensions (axial and radial). The simulation results obtained using our model (and implemented in Verilog-A) have been validated with experimental data from multiple sources. Our work demonstrates the flexibility of including different transport mechanisms in a unified framework.We have characterized valence change memory (VCM) memristors with HfO2 and HfZrO2 as switching layers. They exhibit bipolar switching, negative differential resistance, multiple conductance states, and STDP behaviour, which have been analyzed. We have also modeled the transport in these VCM-based memristors, and simulated the I-V and dynamic switching characteristics, and STDP behaviour in these devices. We have simulated arrays of, both, ECM and VCM devices using the proposed models, and tried to demonstrate a typical pattern classification problem using in-memory computation. We believe that our models provide useful insight into the design of memristors for neuromorphic and memory applications.

Enhanced resistive switching characteries in HfOx memory devices by embedding W nanoparticles

Resistive random access memory (RRAM) has lots of advantages that make it a promising candidate for ultra-high-density memory applications and neuromorphic computing. However, challenges such as high forming voltage, low endurance, and poor uniformity have hampered the development and application of RRAM. To improve the uniformity of the resistive memory, this paper systematically investigates the HfOx-based RRAM by embedding nanoparticles. In this paper, the HfOx-Based RRAM with and without tungsten nanoparticles (W NPs) is fabricated by magnetron sputtering, UV lithography, and stripping. Comparing the various resistive switching behaviors of the two devices, it can be observed that the W NPs device exhibits lower switching voltage (including a 69.87% reduction in Vforming and a reduction in Vset/Vreset from 1.4 V/-1.36 to 0.7 V/-1.0 V), more stable cycling endurance (&gt;105 cycles), and higher uniformity. A potential switching mechanism is considered based on the XPS analysis and the research on the fitting of HRS and LRS: Embedding W NPs can improve the device performance by inducing and controlling the conductive filaments (CFs) size and paths. This thesis has implications for the performance enhancement and development of resistive memory.

Model-based Optimization of the Switching Performance of a Switch Disconnector

Low voltage switch disconnectors (SD) combine rated load switching with disconnector functionality, providing safe electrical isolation. Electrical contacts are separated forming an arc discharge that needs to be quenched at first current zero (CZ) to protect the load and the SD itself. With increased line voltage, interruption at first CZ crossing is getting more difficult due to increased transient recovery voltage (TRV) and larger post arc current, leading to excessive contact erosion with longer arcing time. Arc simulation methodology was utilized to improve the design for better arc cooling close to CZ. Therefore, benchmark values of arc resistance and thermal time constant were evaluated close to CZ for a successful test at lower line voltage. The cooling efficiency of different designs at higher line voltage was analyzed by 3D arc simulation. A revised design was able to clear overload currents at lower and higher line voltages at first CZ, preventing excessive contact damage.

Low turn-on voltage and high isolation RF MEMS switches for coding metamaterial

Low turn-on voltage and high isolation RF MEMS switches for coding metamaterial

Capacitor ripple reduction in T-type multilevel inverter operation for solar PV-application

Efficient and reliable power electronic converters are desired to integrate renewable energy sources into households or the grid. Multilevel inverters for their benefits are being explored for low-power applications. In this work, recently introduced 9-level T-Type switched-capacitor multilevel inverters are explored for 11-level operation, increasing their reliability in high-temperature conditions. The operation makes it capable of generating more voltage levels than the prior technology and diminishes capacitor inrush currents. Eventually, in 9-level operation, the undesired continuous high inrush current peaks are inevitable, which heat the capacitors due to electrolytic series resistance (ESR). This leads to early electrolyte evaporation and thus results in capacitance variation and an increase of ESR with time. In order to suppress the capacitor inrush currents, additional inductance of small value in the charging circuit is sought to mitigate these currents, but that leads to increased losses and increased switch ringing effect. In this work, the modulation of the inverter is performed to produce 11-levels at the inverter output. Inverter redundant states are so employed that the capacitors are always charged and discharged through the load. This results in reduction of inrush current peaks by approximately 20 times, thereby increasing the reliability and life of the inverter and making them more suitable for Solar PV applications in harsh weather conditions. This structure and modulation strategy also achieves lower switch voltage and current stresses. The improved topology and the modulation strategy are validated on the controller hardware-in-the-loop (CHIL) setup and PLECS environments. Further, the topologies are experimentally validated on a laboratory prototype.

Hydrogen Bonding-Assisted Complete Ferroelectric β-Phase Conversion in Poly(vinylidene fluoride) Thin Films: Exhibiting an Excellent Memory Window and Long Retention.

Organic nonvolatile memory with low power consumption is a critical research demand for next-generation memory applications. Ferroelectric switching characteristics of poly(vinylidene fluoride) (PVDF) thin films modified with a trace amount of hydrated Cu salt (CuCl2·2H2O) are explored in the present study. Herein, a Cu salt-mediated PVDF (Cu/PVDF) thin film with preferential edge-on β-crystallites is fabricated through the orientation-controlled spin coating (OCSC) technique. This work proposes a convenient and effective approach to produce edge-on-oriented electroactive PVDF thin films with a high degree of polar β-phase, so as to realize the favorable switching under low operating voltages. Herein, chemically modified PVDF is anticipated to form a complex intermediate, which attains its stability by undergoing favorable hydrogen bonding that reorients the C-C structure of PVDF to obtain the β-conformation. Such information is verified by X-ray photoelectron spectroscopy (XPS). Grazing incidence Fourier transform infrared (GI-FTIR) spectroscopy revealed that the Cu salt incorporated into the PVDF matrix favored the formation of the electroactive β-phase with edge-on crystallite lamellae. Consequently, the Cu/PVDF thin film demonstrates a good contrast between electric field-assisted written and erased data bits in the piezoresponse force microscopy (PFM) phase image. Furthermore, to obtain the ferroelectric memory window, a metal-ferroelectric-insulator-semiconductor (MFIS) diode with Cu/PVDF as a ferroelectric layer has been fabricated. The capacitance-voltage (C-V) characteristic of the MFIS diode exhibits a memory window of 12 V with a long-term retention behavior (∼longer than 7 days). In a nutshell, we tried to represent a clear understanding of the interfacial interactions of the Cu salt with PVDF, which favor the edge-on formation that results in the promising low-voltage ferroelectric switching and excellent retention response, where any additional electrical poling and/or external stretching is completely possible to be ruled out, thus offering a new prospect for the evolution of devices with long-lasting nonvolatile memories.

A Reduced Switch Count Seven-Level Boost ANPC Based Grid Following Inverter Topology With Photovoltaic Integration

A boost active-neutral-point-clamped (BANPC) multilevel inverter based on a switched-capacitor network generally shows a bargain between the number of switches and its voltage rating. Moreover, control complexities are increased with the increase in switch count. In this paper, a new single-phase seven-level boosted ANPC (7L-BANPC) topology using 8(eight) switches, one floating capacitor, and one dc source is presented. The proposed inverter is capable of producing 1.5 times voltage boosting and needs a lower switch voltage rating. The efficiency of the proposed inverter is increased significantly due to lower rating switching devices and a reduced number of total conducting switches. The unipolar level-shifted sine pulse width modulation is considered for controlling the proposed inverter. A three-phase single-stage grid-connected SPV system with the proposed 7L-BANPC inverter is implemented. For the proposed system, theoretical analysis and design calculations are illustrated. The steady-state and dynamic performances of the proposed inverter as well as the grid-connected SPV system under different load power factors, modulation indices, and environmental conditions are simulated using the MATLAB/Simulink software and tested using OPAL-RT real-time emulator. A comparison with existing topologies clearly shows the benefits of the proposed inverter.