Switching Devices Research Articles

Ferroelectric polarization and conductance filament coupling for large window and high-reliability resistive memory and energy-efficient synaptic devices

Ferroelectric capacitors hold great promise for non-volatile memory applications. However, the challenge lies in fabricating resistive switching devices with a high on/off ratio, excellent non-volatility, and a simple manufacturing process. Here, a novel approach is introduced by demonstrating the efficacy of the coupling effect between ferroelectric polarization and oxygen vacancy-based conductive filaments in Hf0.5Zr0.5O2 (HZO) films for the creation of non-volatile resistive switching memory devices, achieving an impressive on/off ratio of 6.8 × 103 at +1.8 V. An in-depth exploration of the resistive switching mechanism is provided and subsequently the outstanding durability and retention characteristics of these devices for resistive switching is validated. Furthermore, the device’s capacity to emulate non-volatile synaptic functionalities is assessed. Our results reveal that under pulsed conditions of 1 V/–2 V with 1 µs pulses spaced 50 ms apart, the device can robustly achieve potentiation/depression synaptic plasticity, while exhibiting energy consumption (0.16 fJ for potentiation, 0.12 fJ for depression) reduced by 1–2 orders of magnitude compared to biological synapses. This work holds significant value as a reference for the fabrication of energy-efficient, non-volatile memory and synaptic devices.

Resistive Switching Devices for Neuromorphic Computing: From Foundations to Chip Level Innovations.

Neuromorphic computing has emerged as an alternative computing paradigm to address the increasing computing needs for data-intensive applications. In this context, resistive random access memory (RRAM) devices have garnered immense interest among the neuromorphic research community due to their capability to emulate intricate neuronal behaviors. RRAM devices excel in terms of their compact size, fast switching capabilities, high ON/OFF ratio, and low energy consumption, among other advantages. This review focuses on the multifaceted aspects of RRAM devices and their application to brain-inspired computing. The review begins with a brief overview of the essential biological concepts that inspire the development of bio-mimetic computing architectures. It then discusses the various types of resistive switching behaviors observed in RRAM devices and the detailed physical mechanisms underlying their operation. Next, a comprehensive discussion on the diverse material choices adapted in recent literature has been carried out, with special emphasis on the benchmark results from recent research literature. Further, the review provides a holistic analysis of the emerging trends in neuromorphic applications, highlighting the state-of-the-art results utilizing RRAM devices. Commercial chip-level applications are given special emphasis in identifying some of the salient research results. Finally, the current challenges and future outlook of RRAM-based devices for neuromorphic research have been summarized. Thus, this review provides valuable understanding along with critical insights and up-to-date information on the latest findings from the field of resistive switching devices towards brain-inspired computing.

Observation of nonvolatile magneto-thermal switching in superconductors

Applying a magnetic field to a solid changes its thermal-transport properties. Although such magneto-thermal-transport phenomena are usually small effects, giant magneto-thermal resistance has recently been observed in spintronic materials and superconductors, opening up new possibilities in thermal management technologies. However, the thermal conductivity conventionally changes only when a magnetic field is applied due to the absence of nonvolatility, which limits potential applications of thermal switching devices. Here, we report the observation of nonvolatile thermal switching that changes the electron thermal conductivity when a magnetic field is applied and retains the value even when the field is turned off. This unconventional magneto-thermal switching arises in commercial Sn-Pb solders and is realized by phase-separated superconducting states and resultant nonuniform magnetic flux distributions. This result confirms the versatility of the observed phenomenon and aids the development of active solid-state thermal management devices.

Hydrogen-Driven Low-Temperature Topotactic Transition in Nanocomb Cobaltite for Ultralow Power Ionic-Magnetic Coupled Applications.

We reversibly control ferromagnetic-antiferromagnetic ordering in an insulating ground state by annealing tensile-strained LaCoO3 films in hydrogen. This ionic-magnetic coupling occurs due to the hydrogen-driven topotactic transition between perovskite LaCoO3 and brownmillerite La2Co2O5 at a lower temperature (125-200 °C) and within a shorter time (3-10 min) than the oxygen-driven effect (500 °C, tens of hours). The X-ray and optical spectroscopic analyses reveal that the transition results from hydrogen-driven filling of correlated electrons in the Co 3d-orbitals, which successively releases oxygen by destabilizing the CoO6 octahedra into CoO4 tetrahedra. The transition is accelerated by surface exchange, diffusion of hydrogen in and oxygen out through atomically ordered oxygen vacancy "nanocomb" stripes in the tensile-strained LaCoO3 films. Our ionic-magnetic coupling with fast operation, good reproducibility, and long-term stability is a proof-of-principle demonstration of high-performance ultralow power magnetic switching devices for sensors, energy, and artificial intelligence applications, which are keys for attaining carbon neutrality.

Programmable Threshold Logic Implementations in a Memristor Crossbar Array.

In this study, we demonstrate the implementation of programmable threshold logics using a 32 × 32 memristor crossbar array. Thanks to forming-free characteristics obtained by the annealing process, its accurate programming characteristics are presented by a 256-level grayscale image. By simultaneous subtraction between weighted sum and threshold values with a differential pair in an opposite way, 3-input and 4-input Boolean logics are implemented in the crossbar without additional reference bias. Also, we verify a full-adder circuit and analyze its fidelity, depending on the device programming accuracy. Lastly, we successfully implement a 4-bit ripple carry adder in the crossbar and achieve reliable operations by read-based logic operations. Compared to stateful logic driven by device switching, a 4-bit ripple carry adder on a memristor crossbar array can perform more reliably in fewer steps thanks to its read-based parallel logic operation.

A Soft-Switching Proportional Dimming LED Driver Based on Switched Capacitor

This paper proposes a switched capacitor-based soft-switching proportional dimming LED driver to address color-mixing LED applications. The driver utilizes a half-bridge switch structure and incorporates a switched capacitor to regulate the dual resonant network. This configuration facilitates current sharing across each resonant network and enables fixed proportion dimming between them. The common inductance leveraged in this design results in fewer switching devices, thereby enhancing efficiency. Furthermore, all switches and diodes achieve soft switching, contributing to high efficiency. Finally, this paper built a 19 W experimental prototype, and the maximum efficiency reached 95.56%, which verified the correctness and feasibility of the driver.

Nanophotonic resistive switch based on tapered copper-silicon structure with low power and high extinction ratio

A non-volatile nanophotonic resistive switch in tapered copper-on-silicon structure is proposed with a potential of electrical writing and optical readout. Incorporating tapered hybrid plasmonic structure in the device enables variable areas of the density of conduction filaments in the direction of optical propagation causing enhanced interaction of light with the lossy metal filaments. The tapered Cu-SiO2-Si is shown to have large optical extinction ratio where high mobility of copper ions in thin SiO2 leads to the low power operation. Optical readout of the resistive switching is demonstrated in the 10 nm thin ion conducting layer (SiO2) at a 1550 nm wavelength with well-defined hysteresis curve. Switching between off and on states is attained by voltage induced annihilation/formation of the nanoscale metal filament inside a thin layer of SiO2 sandwiched between copper and silicon. An optical extinction ratio of 18 dB is reported for a 30 μm long device. In addition, the proposed nanophotonic switch exhibits an intrinsic stochastic property of set voltage reduction in each set-reset cycle. High extinction ratio, reduced set voltage, low power consumption, and non-volatility make the device excellent choice for applications in realizing ultra-compact on-chip devices for optical switching, modulation, and neuromorphic computing.

Colossal Magnetoresistive Switching Induced by d0 Ferromagnetism of MgO in a Semiconductor Nanochannel Device with Ferromagnetic Fe/MgO Electrodes.

Exploring potential spintronic functionalities in resistive switching (RS) devices is of great interest for creating new applications, such as multifunctional resistive random-access memory and novel neuromorphic computing devices. In particular, the importance of the spin-triplet state of cation vacancies in oxide materials, which is induced by localized and strong O-2p on-site Coulomb interactions, in RS devices has been overlooked. d0 ferromagnetism sometimes appears due to the spin-triplet state and ferromagnetic Zener's double exchange interactions between cation vacancies, which are occasionally strong enough to make nonmagnetic oxides ferromagnetic. Here, for the first time, anomalous and colossal magneto-RS (CMRS) with very high magnetic field dependence is demonstrated by utilizing an unconventional RS device composed of a Ge nanochannel with all-epitaxial single-crystalline Fe/MgO electrodes. The device shows colossal and unusual behavior as the threshold voltage and ON/OFF ratio strongly depend on a magnetic field, which is controllable with an applied voltage. This new phenomenon is attributed to the formation of d0 -ferromagnetic filaments by attractive Mg vacancies due to the spin-triplet states with ferromagnetic double exchange interactions and the ferromagnetic proximity effect of Fe on MgO. The findings will allow the development of energy-efficient CMRS devices with multifield susceptibility.

Design and Fabrication of Switched Reluctance Motor for Energy Efficient Operation by Minimizing Torque Ripple

Around the world, motor is consuming more than 40% of the total-generated electrical energy. Accordingly, energy efficient electrical drives are the needs of the hour. The Switched Reluctance Motor (SRM) is more energy efficient than other kinds. Since SRM has a rugged structure, it has inherent fault tolerance characteristics and is cost-effective than synchronous and induction machines. Nevertheless, the application of such a motor is limited due to low torque density, torque ripples and power losses because of control circuit. In this research work, the author proposed a novel-designed SRM, which is achieved by optimizing stator and rotor pole arc. Alongside, a novel control circuit, which has single transistor, is proposed. The modification of stator and rotor pole arcs assists in the reduction of the torque ripple. The stator pole arc is modified from 32 degree to 36 degree, and the rotor pole arc is modified from 30 degree to 28 degree. Thus, the torque ripple is reduced from 3.25 to 2.92 Nm, and thus, the useful torque is increased from 4.94 to 5.2 Nm. Furthermore, a single transistor switching device is used instead of the conventional one with four switches. Hence, energy loss on the control circuit is significantly reduced. From the experimental analysis, it is found that, with-pole-arc modified SRM has higher efficiency than the one without it.

Insights into dynamic switching behavior and electric field distribution of depletion-mode GaN HEMT with bonding pad over active layout

Bonding pad over active (BPOA) layout, which stacks traditional horizontal structure pad electrodes vertically above the active area, is an area-effective device architecture and packaging-enabled solution for GaN-based high electron mobility transistors (HEMTs). In this work, the dynamic switching and electric field distribution of such layout, as well as associated capacitance–voltage and trapping characteristics, are comprehensively studied on D-mode GaN-on-sapphire HEMT by performing numerical simulations. In terms of different pad electrodes covering the active area, BPOA is composed of various structures such as gate-related and drain-related BPOAs (i.e. G-BPOA and D-BPOA), among which G-BPOA exhibits inferior switching characteristics due to the additional introduction of Miller capacitance that prolongs the device switching, while breakdown voltage of D-BPOA is 400–900 V lower than other BPOA counterparts due to the interplay between D-BPOA and the drain electrode. Furthermore, the effects of trap capture cross section and trap density on switching characteristics are evaluated. These results highlight the differences in electrical characteristics of various structures within the BPOA layout, and provide valuable insights into BPOA device design and performance improvement.

Planar nanoscale vacuum channel transistors based on resistive switching

Resistance switching (RS) offers promising applications in a variety of areas. In particular, silicon oxide (SiO x ) under RS can serve as electron sources in new types of miniature vacuum electron tubes. In this work, planar nanoscale vacuum channel transistors (NVCTs) with graphene electrodes and RS SiO x electron sources were developed. In each RS-NVCT, the resistance between the ground and the gate underwent high–low–high transitions, which resulted from formation and subsequent rupture of Si conducting filaments. Electrons were emitted from the post-reset Si filaments and the current received by the collector (I C) was well controlled by the gate voltage (V G). The transfer characteristics reveal that I C was quite sensitive to V G when RS occurred. With V G sweeping from 0 to −20 V, the obtained subthreshold swing (SS) of 76 mV dec−1 was quite close to the theoretical limit of the SS of a field effect transistor at room temperature (60 mV dec−1). The largest ON/OFF ratio was of the order of 106. The output characteristics of the devices indicate that the dependence of I C on the collector voltage (V C) weakened at high V C values. These results demonstrate the application potential of RS-NVCTs as either switching devices or amplifiers.

The Robust Ferroelectric and Electrical Response in 2D Bi2O2Se Semiconductor

AbstractThe amelioration of atomically thin ferroelectric materials is imperative for next‐generation outperformed two‐dimensional (2D) electronics, which is elusive by their bulk counterparts. These remarkable materials’ ferroelectric and piezoelectric features are the fundamental urges in optoelectronics, electronics, and energy harvesting. In this work, 2D ferroelectric Bi2O2Se flakes have been synthesized using a modified chemical vapor deposition technique. The 6 nm thick Bi2O2Se flake provides a robust ferroelectric switching under an applied voltage of ±10 V by piezoresponse force microscopy, further confirmed by first principles. Leveraging the successful growth, the high‐quality Bi2O2Se flakes permit the fabrication of a field‐effect transistor (FET) with state‐of‐the‐art performance. The FET device rewards a high current on–off ratio of 108 and field effect mobility of almost 131 cm2 V−1 s−1, owing to the small carrier effective mass of 0.2 m0. Combined, the electric field‐induced local polarization of ferroelectric switching and unprecedented device performance of Bi2O2Se semiconductors are certified for their utilization in advanced nanoelectronics and miniaturization of multifunctional devices with multifunctionalities.

Sodium adsorption on nanometer-thick TiO2 channel thin-film transistors for enhanced drain currents

Sodium adsorption on nanometer-thick-TiO2-channel thin-film transistors (TFTs) are examined for enhancing the drain current. In the TFTs, the channel thickness of TiO2 is set as thin as ∼16 nm. The TiO2 film is deposited by atomic layer deposition using plasma excited humified Ar, followed by crystallization into the anatase phase by thermal annealing at 500 °C in air. The gate oxide is a 300 nm thick SiO2 film, which is grown on a highly doped n+ Si substrate. The n+ Si substrate is used as the gate electrode. The drain and source electrodes of Ti are deposited by an electron beam evaporation at room temperature. The TiO2 channel is covered with multiple layers of aluminum silicate and SiO2 films to enhance the Na sorptivity. The multiple films consist of combinations of 1 nm thick SiO2 and 0.16 nm thick aluminum silicate. The channel length and width are 60 and 1000 μm, respectively. The TFT without the Na adsorption exhibits a field effect mobility of ∼0.5 cm2/V s, where the drain current is recorded around 30 μA with a gate voltage of 10 V. With immersion of the TFT in a 10 mM NaCl solution, the drain current is enhanced to the order of mA. The simulation with an equivalent circuit with source and drain resistances suggests that the field effect mobility is enhanced to ∼30 cm2/V s with the adsorption of Na. In this paper, we discuss the operation mechanism of the Na adsorbed TiO2 TFT and its applicability as TFT-based high current switch devices and sensors.

A Family of DC-DC Converters Based on Y-Source Impedance Network and Boost Module

A novel family of high-gain converters based on the Y-source impedance network is proposed in this paper, providing novel solutions to high voltage gain applications. Compared with the traditional improved Y-source topology, the proposed new topologies relocate the switch from the output side to the input side, which effectively reduces the stress of the switching device, and the topology combines different boost modules, which effectively improves the boost ability. In order to show the characteristics of the proposed topologies, the operating principles and analyses are given detailed in this paper. Experimental results verify the feasibility of the proposed converters.

A Junction Temperature Smoothing Control Method for SiC MOSFETs Based on the Gate Driving Signal Delay

Low frequency junction temperature fluctuation caused by changes in load current or ambient temperature can severely accelerate the aging development and reduce the operational lifetime of power switching devices. Therefore, junction temperature smoothing control (JTSC) is important for high reliability operation. Conventional JTSC methods require complex additional hardware. Moreover, they are invasive with compromising on the output power quality of the converter. To solve these problems, a novel JTSC method is proposed based on the adjustment of the gate driving signal delay ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> ). <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">First</i> , the relationship between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> and the power loss is analyzed. It is discovered that the power loss is positively linear to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> , which is the basis for JTSC. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Second</i> , a JTSC strategy is proposed based on the proportional-integral control. The gate driving signal delay can be adjusted adaptively according to the proposed control algorithm. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Third</i> , the effectiveness of the proposed JTSC method is verified by experiments. The junction temperature fluctuation can be eliminated by 50 % in various load conditions. Compared with conventional JTSC methods, the proposed method has almost no compromising on the output power quality of the converter, and it requires no additional hardware with low cost.

A Study on the Analysis of Factors Affecting Consumer Purchase Intention of Korean Smartphone Brands: Focusing on Cameroon in Central Africa*

Purpose – An increase in the number of smartphone users and the availability of many phone brands has induced consumers to consider device features, the technology acceptance model (TAM), and switching barriers before making a purchase. As such, this paper seeks to investigate the factors (device features and switching barrier) and TAM determinants that influence the consumer satisfaction and purchase intention of smartphones. Additionally, we study the moderating effects that perceived ease of use may have on consumer purchase intention. Design/Methodology/Approach – To this end, the analysis of data (325) through structural equation modeling in AMOS seeks to examine the effect of device features, TAM determinants, and switching barriers on purchase intention. Findings – The findings demonstrate TAM (perceived usefulness) and device features (function and price) influence consumer satisfaction to varying degrees. With regards to switching barrier, switching cost has a positive influence on consumer satisfaction. Perceived ease of use moderates the relationship between device function and search intention. Finally, the study confirms the relationship between consumer satisfaction and purchase intention. Research Implications – Due to the importance of consumer satisfaction in forming purchase intention, companies should try to maximize the satisfaction of customers during interactions by providing device features that meet the need of the customer. Therefore, companies should try to identify the needs of customers. Going by TAM determinants, manufacturers have to ensure that the system technology of the smartphone is most useful for consumer day to day activities.

Multistage converter with reduced switch voltage stress and diode current stress

AbstractThe utilization of switched inductors, involving parallel charging and series discharging of inductors, is extensively embraced in diverse DC–DC converters for attaining high voltage gain; nevertheless, the stress on switch voltage and diode current escalates considerably with an increased count of inductors integrated into the switched inductors network. In the classical multistage switched inductor converter, the switch voltage aligns with the output voltage, and the diode experiences a high current as the number of stages increases. This research recommends a DC–DC multistage converter for energy conversion and high voltage gain with low stress. In this paper, a novel multistage switched inductor converter is introduced and designed to attain higher voltage gain while mitigating the stresses on switch voltage and diode current. The proposed circuit is created by replacing the standard multistage switched inductor converter's possible diodes with power switches. All of the switching devices are connected in such a way that the output voltage and input current are shared by all of the switches and diodes, respectively. As a consequence, the voltage stress on switches and the current stress on diodes are comparatively low, resulting in a high efficiency compared to a typical multistage switched inductor converter. It's interesting to note that the proposed converter and a typical multistage switched inductor converter both require the same amount of components. Different operation modes, analysis, a non‐ideal model, and a comparison of the suggested and recently constructed converters are discussed. The effectiveness and performance of the circuit are validated experimentally.

Two-Dimensional Spin-Crossover Molecular Solid Solutions with Tunable Transition Temperatures across 90 K.

Spin-crossover (SCO) materials exhibit remarkable potential as bistable switches in molecular devices. However, the spin transition temperatures (Tc) of known compounds are unable to cover the entire ambient temperature spectrum, largely limiting their practical utility. This study reports an exemplary two-dimensional SCO solid solution system, [FeIII(H0.5LCl)2-2x(H0.5LF)2x]·H2O (H0.5LX = 5-X-2-hydroxybenzylidene-hydrazinecarbothioamide, X = F or Cl, x = 0 to 1), in which the adjacent layers are adhered via hydrogen bonding. Notably, the Tc of this system can be fine-tuned across 90 K (227-316 K) in a linear manner by modulating the fraction x of the LF ligand. Elevating x results in strengthened hydrogen bonding between adjacent layers, which leads to enhanced intermolecular interactions between adjacent SCO molecules. Single-crystal diffraction analysis and periodic density functional theory calculations revealed that such a special kind of alteration in interlayer interactions strengthens the FeIIIN2O2S2 ligand field and corresponding SCO energy barrier, consequently resulting in increased Tc. This work provides a new pathway for tuning the Tc of SCO materials through delicate manipulation of molecular interactions, which could expand the application of bistable molecular solids to a much wider temperature regime.

An adaptive controller for power quality control in high speed railway with electric locomotives with asynchronous traction motors

Introduction. Power quality in an electric railway system pertains to the dependability, consistency, and purity of the electrical power provided to different components and systems within the railway infrastructure. Assessing power quality offers considerable opportunities to improve the efficiency of railway systems. Problem. Managing the flow of active and reactive power effectively, decreasing harmonic currents, and addressing the negative sequence component are all critical parts of improving power quality for electrified rail systems. As a result, flexible AC transmission systems are the major means of minimizing or decreasing these difficulties. Purpose. This study describes a half-bridge reactive power railway power conditioner (HB-RPC) with a novel Ynev balancing transformer. HB-RPC is made up of four switching devices and two DC capacitors and the compensator’s stability is determined by the operating voltage of the DC-link. Any variations or imbalances in the DC voltage might cause the compensator to operate in an unstable manner. Novelty. Of a novel balanced transformer with HB-RPC in a high-speed railway system with two scenarios. Methods. The study utilized MATLAB/Simulink software for simulation purposes. The system integrates a fuzzy logic controller (FLC) and a PI controller to optimize DC voltage, ensuring its constancy and balance, with the objective of improving the overall stability of the system. Results. The simulation outcomes illustrate the efficacy of the control approach. Through a comparison of results between scenarios (two and four trains) with the PI-based-HB-RPC and the FLC-based-HB-RPC, the system exhibits enhanced stability for the proposed railway system when employing the FLC-based-HB-RPC, compared to a controller based on PI. Practical value. The proposed configuration elucidates its role in enhancing both the dynamic performance of the system and the power quality of the three-phase rail traction chain.

Smart current control of the wind energy conversion system based permanent magnet synchronous generator using predictive and hysteresis model

Introduction. Given the increasing demand for performance and efficiency of converters and power drives, the development of new control systems must take into account the real nature of these types of systems. Converters and dimmers power are nonlinear systems of a hybrid nature, including elements linear and nonlinear and a finite number of switching devices. Signals input for power converters are discrete signals that control the ‘opening and closing’ transitions of each component. Problem. In the multilevel inverters connected to grid, the switching frequency is the principal cause of harmonics and switching losses, which by nature, reduces the inverter’s efficiency. Purpose. For guarantee the satisfying quality of power transmitted to the electrical grid, while ensuring reduction of current ripples and output voltage harmonics. Novelty. This work proposes a new smart control, based on a predictive current control of the three level neutral point clamped inverter, used in Wind Energy Conversion System (WECS) connected to grid, based permanent magnet synchronous generator, powered by a hysteresis current control for the rectifier. This new formula guarantees handling with the influence of harmonics disturbances (similar current total harmonic distortion), voltage stress, switching losses, rise time, over or undershoot and settling time in WECS. Methods. The basic idea of this control is to choose the best switching state, of the power switches, which ameliorates the quality function, selected from order predictive current control of WECS. Results. Practical value. Several advantages in this intelligent method, such as the fast dynamic answer, the easy implementation of nonlinearities and it requires fewer calculations to choose the best switching state. In addition, an innovative algorithm is proposed to adjust the current ripples and output voltage harmonics of the WECS. The performances of the system were analyzed by simulation using MATLAB/Simulink.