Switching Devices Research Articles

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.

Analysis of high‐frequency electromagnetic ringing phenomenon under GaN‐FET inverter excitation

AbstractIn this study, the ringing phenomenon of gallium nitride‐field effect transistor (GaN‐FET) and silicon‐insulated gate bipolar transistor (Si‐IGBT) inverter excitations in a ring sample was thoroughly measured and analyzed by using a high‐quality oscilloscope with a very high sampling rate of 5 giga‐samples per second (GS/s). Owing to the rapid switching of the GaN‐FET power devices in several nanoseconds and the ringing frequencies in the MHz range, the use of the high sampling rate of 5 GS/s is necessary and useful for accurate measurement. The experimental findings and analysis reveal the following three key points: (i) there are two possible types of high‐frequency resonance phenomena, that is, the first one caused by semiconductor devices and circuits and the other generated by the resonance with loads in use. (ii) The ringing phenomenon because of the resonance under the load is considered to be due to the rising time of pulses that are caused by the rapid switching of the semiconductor devices. (iii) The ability to measure and the two types of ringing phenomena depends on the intensity of the white noise of the measuring instrument

Fast colour switching of asymmetric electrochromic devices

Electrochromic (EC) devices based on conjugated polymers (CPs) with optical activity was developed. Asymmetric EC polymers are synthesised through electrochemical polymerisation in cholesteric liquid crystals (CLCs). This asymmetric polymerisation method transcribes the helical structure of CLCs to CPs. The EC performance of chiral EC polymers remains insufficiently explored. This study elucidated the impact of the electronic and structural properties of chiral EC polymers on their EC performances, focusing on optical contrast, response time, and cycle stability. Compared with 3,4-(ethylenedithia)thiophene (EDTT) units with an electron-withdrawing group, 3,4-(ethylenedioxy)thiophene (EDOT) units with an electron-donating group exhibited a stable oxidation state, enhanced cycle stability, and accelerated response time. Moreover, 3,4-(propylenedioxy)thiophene adorned with bulky methyl groups (dMProDOT) had a higher EC performance, characterised by a bleaching/colouring time of 1.1 s and high cycle stability. The EC performance of these asymmetric EC polymers was significantly influenced by the structural and electrical properties of the constituent units. The findings of this study provide valuable molecular design guidelines for the application and optimisation of the asymmetric EC polymers.

A self-selecting memory element based on a method of interconnected ovonic threshold switching device

A self-selecting memory element based on a method of interconnected ovonic threshold switching device

Modulation Techniques and Coordinated Voltage Vector Distribution: Effects on Efficiency in Dual-Inverter Topology-Based Electric Drives

The increasing popularity of electric drives employing an isolated dual-inverter (DI) topology is motivated by their superior DC-link voltage and power utilization, fault-tolerant operation, and potential for multilevel operation. These attributes are significant in battery-powered transportation, such as electric vehicles and aviation. Given the considerable freedom in modulation and control of the DI topology, this paper researches the impact of reference voltage vector distribution between the two individual inverters. The study also evaluates the influence of two well-established asynchronous modulation strategies—Space Vector PWM (SVPWM) and Depenbrock’s Discontinuous Modulation (DPWM1). Since simulation tools nowadays play a crucial role in power electronics design and concept verification, the results are based on extensive and detailed models in Matlab/Simulink. Employing the basic field-oriented control of a 12 kW induction motor with precisely parameterized SiC switching devices for accurate loss calculation, this research reveals the possibility of significant energy savings at multiple operating points. Notably, optimal efficiency is achieved when one inverter operates up to half of the nominal speed while the other solely establishes a neutral point for the winding. Moreover, the results highlight DPWM1 as a superior strategy for the DI topology, showcasing reduced converter losses. Overall, it is shown that the system’s losses can be significantly reduced just by the design of the voltage vector distribution in the drive’s operating range and the modulation strategy selection.

Photooxidation driven formation of Fe-Au linked ferrocene-based single-molecule junctions

Metal-metal contacts, though not yet widely realized, may provide exciting opportunities to serve as tunable and functional interfaces in single-molecule devices. One of the simplest components which might facilitate such binding interactions is the ferrocene group. Notably, direct bonds between the ferrocene iron center and metals such as Pd or Co have been demonstrated in molecular complexes comprising coordinating ligands attached to the cyclopentadienyl rings. Here, we demonstrate that ferrocene-based single-molecule devices with Fe-Au interfacial contact geometries form at room temperature in the absence of supporting coordinating ligands. Applying a photoredox reaction, we propose that ferrocene only functions effectively as a contact group when oxidized, binding to gold through a formal Fe3+ center. This observation is further supported by a series of control measurements and density functional theory calculations. Our findings extend the scope of junction contact chemistries beyond those involving main group elements, lay the foundation for light switchable ferrocene-based single-molecule devices, and highlight new potential mechanistic function(s) of unsubstituted ferrocenium groups in synthetic processes.

Controlled single-phase auto-reclosing technique for shunt reactor compensated lines in electrical energy systems transmission lines

A new controlled Single-Phase Auto Reclosing (SPAR) technique for Shunt Reactor Compensated Transmission Line (SRCTL) in electrical energy systems is presented in this paper. The suggested technique uses a Circuit Breaker (CB) with a Controlled Switching Device (CSD) and a Pre-Insertion Resistor (PIR). This said type of combination is available without any additional investment in the substation designed at 220 kV and above. The proposed technique performs Fourier Transform (FT) analysis of the acquired discrete samples of line side voltage of faulty phase during the Dead/Deionised Time of CB (DTCB). Furthermore, an assessment of the suggested scheme is done by generating a model similar to the present 400 kV, SRCTL in the PSCAD software environment. Moreover, the suggested scheme has been evaluated considering wide variation in parameters such as line length, compensation level, period of fault, fault inception angle, position of fault, effect of Switching Arrestor (SA) and the effect of different grid sources. At last, a comparison between the suggested scheme and the reported technique indicates the effectiveness of the suggested scheme when the Operating Time Scatter (OTS) (± 1 ms) of CB is taken into account.

The Time Response Analysis of a Hybrid Electronic Switch and Residual Current Devices System

The Time Response Analysis of a Hybrid Electronic Switch and Residual Current Devices System

Thermal Compact Modeling and Resistive Switching Analysis in Titanium Oxide-Based Memristors.

Resistive switching devices based on the Au/Ti/TiO2/Au stack were developed. In addition to standard electrical characterization by means of I-V curves, scanning thermal microscopy was employed to localize the hot spots on the top device surface (linked to conductive nanofilaments, CNFs) and perform in-operando tracking of temperature in such spots. In this way, electrical and thermal responses can be simultaneously recorded and related to each other. In a complementary way, a model for device simulation (based on COMSOL Multiphysics) was implemented in order to link the measured temperature to simulated device temperature maps. The data obtained were employed to calculate the thermal resistance to be used in compact models, such as the Stanford model, for circuit simulation. The thermal resistance extraction technique presented in this work is based on electrical and thermal measurements instead of being indirectly supported by a single fitting of the electrical response (using just I-V curves), as usual. Besides, the set and reset voltages were calculated from the complete I-V curve resistive switching series through different automatic numerical methods to assess the device variability. The series resistance was also obtained from experimental measurements, whose value is also incorporated into a compact model enhanced version.

Light and voltage dual-modulated volatile resistive switching in single ZnO nanowires.

A single ZnO nanowire device with volatile resistive switching behavior has been prepared. Different from traditional resistive switching devices, such ZnO nanowire devices do not exhibit resistive switching behaviors under a single bias voltage, and appear resistive switching behavior under the combined action of light stimuli and bias voltage. Through the demonstration of the time-dependent hysteresis curve and atmosphere-dependent hysteresis loop of the resistive switching devices, it is believed that under the resistive switching process, ultraviolet illumination can increase the carrier concentration and modulate the barrier depletion structure, and external bias voltage can ionize the surface state. They work together to modulate the switching process of the devices. Such light stimuli and bias voltage dual-modulated resistive switching device enables optical control and may thus be considered for sensory applications or optically tunable memories.

An improved state‐space average model of the ultra‐high voltage inverter based on wavelet decomposition and reconstruction

SummaryUltra‐high voltage inverters are widely used as grid‐connected devices in new energy grids, and the state‐space average model is the most practical modeling method for the inverter. However, the accuracy of this modeling method is significantly reduced because it ignores the high‐frequency switching process, which contains overshoot voltage and other factors that affect system stability. Moreover, the amplitude of the overshoot voltage in the ultra‐high voltage inverter will be huge, which may lead to the damage to switching devices, circuit overheating, and even the collapse of the system. Therefore, the wavelet decomposition and reconstruction methods are used in this paper to extract the transient characteristics of the inverter and integrate them into the state‐space average model. Compared with the traditional state‐space average model, the improved model method can obtain a more accurate overshoot voltage peak value with the same simulation step size. Then, it can provide a more precise reference for the withstand voltage in the device selection of a high voltage level system. The single‐phase full‐bridge inverter is taken as an example to illustrate the construction process based on the wavelet decomposition and reconstruction method. Finally, the simulation waveform is verified to be in good agreement with the experiment.