Switching Performance Research Articles

A High‐Entropy‐Oxides‐Based Memristor: Outstanding Resistive Switching Performance and Mechanisms in Atomic Structural Evolution (Adv. Mater. 41/2023)

A High‐Entropy‐Oxides‐Based Memristor: Outstanding Resistive Switching Performance and Mechanisms in Atomic Structural Evolution (Adv. Mater. 41/2023)

Analysis of SiC/Si Heterojunction Band Energy and Interface State Characteristics for SiC/Si VDMOS.

SiC/Si and GaN/Si heterojunction technology has been widely used in power semiconductor devices, and SiC/Si VDMOS and GaN/Si VDMOS were proposed in our previous paper. Based on existing research, breakdown point transfer technology (BPT) was used to optimize SiC/Si VDMOS. Simulation results showed that the BV of the SiC/Si heterojunction VDMOS was considerably increased from 259 V to 1144 V, and Ron,sp decreased from 18.2 mΩ·cm2 to 6.03 mΩ·cm2 compared with Si VDMOS. In order to analyze the characteristics of the SiC/Si heterojunction structure deeply, the influence of the interface state characteristics of the SiC/Si heterojunction on the electrical parameters of VDMOS was analyzed, including electric field characteristics, blocking characteristics, output characteristics, and transfer characteristics. In addition, the influence of the interface state of the SiC/Si heterojunction on energy band characteristics was analyzed. The results showed that with an increase in the interfacial charge (acceptor) concentration, the p-type trap layer was introduced into the interface of the SiC/Si heterojunction, energy increased slightly, and the barrier height difference at the heterojunction increased, resulting in an increase in BV. At the same time, since the barrier height became higher, electrons did not flow easily, so Ron,sp increased. On the contrary, when a charge (donor) was introduced at the interface of the SiC/Si heterojunction, the number of electrons in the channel increased, resulting in an increase in the electron current, which is conducive to the flow of electrons, resulting in a decrease in Ron,sp. The energy band and other characteristics of devices with temperature were simulated at different temperatures. Finally, the effects of SiC/Si heterojunction interface states on interface capacitances and switching performances of VDMOS devices were also discussed.

Influences of Cu Doping on the Microstructure, Optical and Resistance Switching Properties of Zinc OxideThin Films.

Copper-doped zinc oxide films (Zn1-xCuxO) (x = 0, 2%, 4%, 6%) were fabricated on conductive substrates using the sol-gel process. The crystal structure, optical and resistive switching properties of Zn1-xCuxO films are studied and discussed. RRAM is made using Zn1-xCuxO as the resistive layer. The results show that the (002) peak intensity and grain size of Zn1-xCuxOfilms increase from 0 to 6%. In addition, PL spectroscopy shows that the oxygen vacancy defect density of Zn1-xCuxO films also increases with the increase in Cu. The improved resistive switching performance of the RRAM device can be attributed to the formation of conductive filaments and the destruction of more oxygen vacancies in the Zn1-xCuxO film. Consequently, the RRAM device exhibits a higher low resistance state to high resistance state ratio and an HRS state of higher resistance value.

Strain-mediated voltage controlled magnetic anisotropy based switching for magnetic memory applications

Reliability and packing density concerns are the two major shortcomings of spin transfer torque and spin orbit torque based magnetic memory, respectively. Voltage controlled magnetic anisotropy (VCMA) becomes energy efficient and fast, showing transcendence for the writing mechanism in the magnetic tunnel junction. Deterministic switching cannot be achieved by VCMA alone in the out of plane nanomagnet. It requires an external in-plane magnetic field, but the use of an external field is inconvenient for on-chip applications. We exploit stress and exchange bias provided by an antiferromagnetic material to mitigate the external magnetic field requisite. We perform macro-spin simulations using the Landau–Lifshitz–Gilbert equation at room temperature. We use the VCMA effect cum stress effect to investigate field free switching performance, and this improves the write error rate (WER) to 5×10−5 against WER of 0.1 with the VCMA effect alone. We studied the effects of applied voltage (amplitude and pulse width), exchange bias field, and VCMA coefficient on the switching performance in detail. This proposed two-terminal device can be helpful in achieving high cell density to implement nonvolatile magnetic memory.

The Fast and One-Step Growth of ZnO Nanorods on Cellulose Nanofibers for Highly Sensitive Photosensors.

Cellulose is the most abundant organic material on our planet which has a key role in our daily life (e.g., paper, packaging). In recent years, the need for replacing fossil-based materials has expanded the application of cellulose and cellulose derivatives including into electronics and sensing. The combination of nanostructures with cellulose nanofibers (CNFs) is expected to create new opportunities for the development of innovative electronic devices. In this paper, we report on a single-step process for the low temperature (<100 °C), environmentally friendly, and fully scalable CNF-templated highly dense growth of zinc oxide (ZnO) nanorods (NRs). More specifically, the effect of the degree of substitution of the CNF (enzymatic CNFs and carboxymethylated CNFs with two different substitution levels) on the ZnO growth and the application of the developed ZnO NRs/CNF nanocomposites in the development of UV sensors is reported herein. The results of this investigation show that the growth and nature of ZnO NRs are strongly dependent on the charge of the CNFs; high charge promotes nanorod growth whereas with low charge, ZnO isotropic microstructures are created that are not attached to the CNFs. Devices manufactured via screen printing/drop-casting of the ZnO NRs/CNF nanocomposites demonstrate a good photo-sensing response with a very stable UV-induced photocurrent of 25.84 µA. This also exhibits excellent long-term stability with fast ON/OFF switching performance under the irradiance of a UV lamp (15 W).

An Integrated Control Approach for Shifting Process of Single-Axis Parallel Hybrid Electric Vehicle with a Multi-Speed AMT Gearbox

When a single-axis parallel hybrid electric vehicle (HEV) equipped with a multi-speed AMT gearbox is in its shifting process, the superposition of dynamic characteristics of multiple power sources and the intervention and withdrawal of AMT transmissions can easily cause significant vehicle longitudinal jerk. To achieve rapid and smooth output changes during the shifting process, this paper proposes an integrated multi-stage robust shifting control method for a single-axis parallel hybrid electric vehicles with a multi-speed AMT gearbox. First, models of key driveline components are constructed, and the shifting process is divided into five stages to provide a clear description of the control problem. Subsequently, we reproduce an integrated multistage robust control method to achieve favorable switching performance and control robustness under external disturbances. We propose a data-driven model predictive control strategy based on additional constraints in the torque unloading and recovery phases. Simultaneously, we present a joint control algorithm that integrates the optimal control and disturbance suppression in the speed synchronization phase. In addition, we develop a sliding mode auto-disturbance rejection control algorithm to achieve accurate position tracking of the shift actuator in the pickup and engage phases. Finally, simulations and bench tests are carried out to verify the effectiveness of the robust control method under different driving conditions. The results demonstrate that the proposed control method can not only coordinate the torque across different power sources and clutch while minimizing vehicle longitudinal jerk, shift time, and friction work, but also provides apparent robustness to model uncertainties and external disturbance. Therefore, the proposed method may offer a theoretical reference for the actual vehicle controller during shifting.

Material to system-level benchmarking of CMOS-integrated RRAM with ultra-fast switching for low power on-chip learning

Analog hardware-based training provides a promising solution to developing state-of-the-art power-hungry artificial intelligence models. Non-volatile memory hardware such as resistive random access memory (RRAM) has the potential to provide a low power alternative. The training accuracy of analog hardware depends on RRAM switching properties including the number of discrete conductance states and conductance variability. Furthermore, the overall power consumption of the system inversely correlates with the RRAM devices conductance. To study material dependence of these properties, TaOx and HfOx RRAM devices in one-transistor one-RRAM configuration (1T1R) were fabricated using a custom 65 nm CMOS fabrication process. Analog switching performance was studied with a range of initial forming compliance current (200–500 µA) and analog switching tests with ultra-short pulse width (300 ps) was carried out. We report that by utilizing low current during electroforming and high compliance current during analog switching, a large number of RRAM conductance states can be achieved while maintaining low conductance state. While both TaOx and HfOx could be switched to more than 20 distinct states, TaOx devices exhibited 10× lower conductance, which reduces total power consumption for array-level operations. Furthermore, we adopted an analog, fully in-memory training algorithm for system-level training accuracy benchmarking and showed that implementing TaOx 1T1R cells could yield an accuracy of up to 96.4% compared to 97% for the floating-point arithmetic baseline, while implementing HfOx devices would yield a maximum accuracy of 90.5%. Our experimental work and benchmarking approach paves the path for future materials engineering in analog-AI hardware for a low-power environment training.

Improvement of memristive switching of Pb(Zr0.52Ti0.48)O3/Nb:SrTiO3 heterostructures via La doping

The ferroelectric memory with superior stability and high operating speed has broad development prospects in areas such as neural computing and information storage. An effective strategy to improve the performance of the resistive switching (RS) of the ferroelectric memory is to improve the conductivity of ferroelectric thin films while maintaining their ferroelectric properties, because there is a competition between ferroelectric properties and conductivity in the RS behavior. Herein, we prepared La-doped Pb(Zr0.52Ti0.48)O3 (PLZT) thin films on the Nb:SrTiO3 (NSTO) substrate. By controlling La concentration, a compromise between ferroelectricity and conductivity was achieved. The RS on/off ratio reached 2.6 × 104 doped with 2 mol% La. Moreover, the conduction mechanism changes from the Schottky emission controlling PZT/NSTO interface to the coexistence of Schottky emission and space charge-limited mechanism in the PLZT/NSTO heterostructures. The results reveal that the effective matching of the ferroelectricity and conductivity of ferroelectric thin films is necessary for obtaining high RS on/off ratio, which is helpful to the accurate design of high-performance ferroelectric memory devices.

Search Method of Robust Gate Driving Vectors for Digital Gate Drivers With Low Test Cost Against Load Current and Temperature Variations in IGBTs

A digital gate driver with active gate driving is effective in solving the trade-off between switching loss and current/voltage overshoot of power devices. However, the optimum gate driving vector (GV) for a digital gate driver is temperature- and load current-dependent. When an optimum GV at a particular operating condition is reused to another, the switching performance sometimes becomes worse than the conventional gate drive [17]. Therefore, robust gate driving vectors (RGV) against temperature and load current variation are required [18]. Nevertheless, the test cost of searching for an RGV is very high. In order to reduce the test cost, search methods of RGV with fewer required measurements are proposed in this work. Single-step GV and stop-and-go GV are selected as the type of RGV for turn-on and turn-off, respectively. Compared with the conventional search method of RGV in [18] and [20], the proposed search method can reduce the measurement time by 99 % and 92 %, respectively. Furthermore, when the RGV and the optimum GV at a single condition are reused to other operating conditions, the maximum overall <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OBJ</sub> of RGV is lower than that of the single condition optimum GV, which shows that the searched RGV has better robustness.

A Novel Non-Isolated Dual-Input Single-Output High Step-Up DC/DC Converter With Coupled Inductors

This paper proposes a novel non-isolated dual-input single-output high step-up DC/DC converter with coupled inductor (NI-DISO-CI) for the distributed sources. The coupled inductor along with the passive clamp circuits is employed to the NI-DISO-CI, which can achieve the high voltage conversion ratio without operating at an extremely duty cycle. The energy stored in leakage inductor is recycled by the passive clamp circuits, which can minimize the voltage spikes across power switches. Therefore, the power switches with low parasitic parameters can be selected. And the power switches can achieve the zero current switching (ZCS) performance by utilizing the leakage inductor from coupled inductor. The operating principle, steady-state analysis, design and performance of the NI-DISO-CI are described in detail. Finally, the experimental prototype with the switching frequency of 100 kHz and the power rating of 400W is built to verify the accuracy of the theoretical analysis.

A High-Entropy-Oxides-Based Memristor: Outstanding Resistive Switching Performance and Mechanisms in Atomic Structural Evolution.

The application of high-entropy oxide (HEO) has attracted significant attention in recent years owing to their unique structural characteristics, such as excellent electrochemical properties and long-term cycling stability. However, the application of resistive random-access memory (RRAM) has not been extensively studied, and the switching mechanism of HEO-based RRAM has yet to be thoroughly investigated. In this study, HEO (Cr, Mn, Fe, Co, Ni)3 O4 with a spinel structure is epitaxially grown on a Nb:STO conductive substrate, and Pt metal is deposited as the top electrode. After the resistive-switching operation, some regions of the spinel structure are transformed into a rock-salt structure and analyzed using advanced transmission electron microscopy and scanning transmission electron microscopy. From the results of X-ray photoelectron spectroscopy and electron energy loss spectroscopy, only specific elements would change their valence state, which results in excellent resistive-switching properties with a high on/off ratio on the order of 105 , outstanding endurance (>4550 cycles), long retention time (>104 s), and high stability, which suggests that HEO is a promising RRAM material.

Impact of age of onset on bilinguals’ task switching performance in a nonimmigration context

It is not clear whether bilingualism leads to task switching benefits in single-language nonimmigration contexts, as in dual-language and code-switching immigration contexts. Ninety young Persian-speaking monolingual and bilingual adults reported their language proficiency and use, with the early bilinguals indicating a balanced rating for their L1 and L2, and late bilinguals reporting slightly higher ratings for L1, relative to L2. Concerning the onset age of bilingualism, the bilinguals were classified as early and late bilinguals according to whether they initiated active regular use of the two languages before or after the age of eight. A nonverbal alternating-runs task switching paradigm was used to measure global switch cost (GSC) and local switch cost (LSC). The findings revealed a slight nonsignificant GSC but a significantly lower LSC for early bilinguals, compared to monolinguals, suggesting that bilingualism effects on task switching do not transpire uniformly across different contexts.

(Invited) Fabrication and Device Performance of 2.7 Kv/2.5A NiO/Ga2O3 Heterojunction Power Rectifiers

In this study, The fabrication of a p-n junction NiO/Ga2O3 rectifier in which we employ a bilayer NiO structure with two different doping levels to achieve both high breakdown voltage and low on-state resistance was described. The band alignment of the NiO to the Ga2O3 was measured. Selective wet and dry etch processes for removing NiO from the underlying Ga2O3 was developed. Finally, the dc and switching performance of the rectifiers was characterized. The maximum breakdown voltage was 2.7 kV for a 1 mm diameter rectifier, with 2.5 A forward current and on/off ratio > 108 over a broad range of switching voltages. The reverse recovery time was limited by the measurement circuit but was < 100 µs. These results show the promise of heterojunction rectifiers based on Ga2O3 for future generations of power switching applications. Figure 1

Fabrication of AIE Polymer-Functionalized Reduced Graphene Oxide for Information Storage.

Reduced graphene oxide (RGO) has been extensively studied and applied in optoelectronic systems, but its unstable dispersion in organic solvents has limited its application. To overcome this problem, the newly designed and developed aggregation-induced emission (AIE) material poly[(9,9-bis(6-azidohexyl)-9H-fluorene)-alt-(9-(4-(1,2,2-triphenylvinyl)phenyl)-9H-carbazole)] (PAFTC) was covalently grafted onto RGO to produce (PFTC-g-RGO). The solubility of two-dimensional graphene was improved by incorporating it into the backbone of PAFTC to form new functional materials. In resistive random access memory (RRAM) devices, PFTC-g-RGO was used as the active layer material after it was characterized. The fabricated Al/PFTC-g-RGO/ITO device exhibited nonvolatile bistable resistive switching performances with a long retention time of over 104 s, excellent endurance of over 200 switching cycles, and an impressively low turn-ON voltage. This study provides important insights into the future development of AIE polymer-functionalized nanomaterials for information storage.

Facile one-pot electropolymerization of novel Cu complexed conducting polymer for Resistive Random Access Memory

An innovative one-pot electrochemical method has been studied for the Polypyrrole-Cu (PPy-Cu) composite films synthesis as the active layer of the Resistive Random Access Memory (ReRAM). Cu has been uniformly distributed in PPy-Cu composite films and exhibits two valence states of Cu (0) and Cu (II). The existence of Cu (II) is beneficial for keeping stable resistive switching performance. The Pt/PPy-Cu/Pt ReRAM device exhibits excellent memory performance with a low threshold voltage, a long retention time and good endurance cycles. The resistive switching mechanism is dominated by the Space Charge Limited Current (SCLC) effect accompanied by Schottky emission.

Factors and Underlying Mechanisms That Influence the Repetitive Breakdown Characteristics of Corona-Stabilized Switches

The corona-stabilized switch has the potential to be a high repetition rate pulsed-power switching device, but there has been limited investigation into its repetitive breakdown stability and insulation recovery characteristics. Repetitive breakdowns of gas are characterized by a memory effect, where the subsequent breakdown process is inevitably influenced by the preceding one. However, there are still some issues that require further exploration in the current research on the mechanism of memory effect on repetitive breakdown characteristics. To clarify the factors and mechanisms that affect the repetitive breakdowns of corona-stabilized switches, this paper introduced optical observation methods into the experimental investigation. Through optical–electrical coupled diagnosis, the repetitive breakdown stability and insulation recovery performance of corona-stabilized switches under different working conditions and repetition frequencies were analyzed. The monotonic promoting effect of corona stabilization on switch insulation strength recovery is proposed as well as the non-monotonic and complex regulatory mechanism of corona stabilization on repetitive breakdown stability. The research results provide a theoretical and practical basis for clarifying the mechanism of repetitive corona-stabilized breakdowns and optimizing the design of corona-stabilized switches.

Graphene Quantum Dots as an Oxygen Reservoir for Topotactic Phase Transition‐Based Memristive Devices

AbstractA novel class of transition metal oxides, capable of reversible topotactic phase transition between the oxygen‐deficient brownmillerite and oxygen‐rich perovskite, has emerged as a promising material for memristive and magnetoelectric devices. However, the absence of a local oxygen source in the device structure necessitates an oxygen exchange process between the surrounding atmosphere and the switching layer during operation, which can lead to unreliable device performance. In this study, graphene quantum dots (GQDs) are introduced into a SrFe0.5Co0.5Ox memristive device as an oxygen reservoir for the nanoscale topotactic redox process. The SrFe0.5Co0.5Ox memristive devices with GQDs exhibit reliable resistive switching performance compared to SrFe0.5Co0.5Ox devices without GQDs. To understand the effect of GQDs on the device structure, a pulse endurance test is carried out in a high vacuum. The devices with GQDs show rather good endurance behavior, while devices without GQDs exhibit endurance failure. These results provide a deeper understanding of the potential use of GQDs in enhancing the performance of SrFe0.5Co0.5Ox memristive devices, with implications for tuning nanoscale topotactic phase transition for multi‐functional properties.

Tin perovskite transistors and complementary circuits based on A-site cation engineering

Tin halide perovskites have the general chemical formula ASnX3, where A is a monovalent cation and X is a monovalent halide anion. These semiconducting materials can be used to fabricate p-type transistors at low cost and temperature and could be potentially integrated with n-type oxide-based transistors to create complementary circuits. However, the materials suffer from low crystallization controllability and high film defect density, resulting in uncompetitive device performance. Here we show that pure-tin perovskite thin-film transistors can be created using triple A cations of caesium–formamidinium–phenethylammonium. The approach leads to high-quality cascaded tin perovskite channel films with low-defect, phase-pure perovskite/dielectric interfaces. The optimized thin-film transistors exhibit hole mobilities of over 70 cm2 V−1 s−1 and on/off current ratios of over 108, which are comparable with commercial low-temperature polysilicon transistors. The transistors are fabricated using solution-processing methods at temperatures no higher than 100 °C. We also integrate the devices with n-type metal oxide transistors to create complementary inverters with voltage gains of 370, and NOR and NAND logic gates with rail-to-rail switching performance.

Three Iodoargentate-Based Hybrids Decorated by Metal Complexes: Structures, Optical/Photoelectric Properties and Theoretical Studies.

So far, the development of new iodoargentate-based hybrids, especially those compounds with metal complex cations, and the understanding of their structure-activity relationships have been of vital importance but full of challenges. Herein, using the in-situ-generated metal complex cations as structural directing agents, three new iodoargentate-based hybrids, namely, [Co(phen)3]Ag2PbI6 (phen = 1,10-phenanthroline; 1), [Ni(5,5-dmpy)3]Ag7I9·CH3CN (5,5-dmpy = 5,5-dimethyl-2,2-bipyridine; 2) and [Co(5,5-dmpy)3]Ag5I8 (3), have been solvothermally prepared and then structurally characterized. Compound 1 represents one new heterometallic Ag-Pb-I compound characteristic of the chain-like [Ag2PbI6]n2n- anions. Compound 2 features the straight one-dimensional (1D) [Ag7I9]n2n- anionic moieties, while compound 3 contains infrequent two types of curved [Ag5I8]n3n- anions. Optical properties reveal that the title compounds exhibit interesting semiconductor behaviors with the band gaps of 1.59-2.78 eV, which endow them with good photoelectric switching performances under the alternate light irradiations. We also present their Hirshfeld surface analyses, and the theoretical studies (band structures, density of states (DOS) and partial density of states (PDOS)).

An Optimized Switching Strategy Based on Gate Drivers with Variable Voltage to Improve the Switching Performance of SiC MOSFET Modules

This paper proposes an optimized switching strategy (OSS) based on a silicon carbide (SiC) MOSFET gate driver with variable voltage, which allows simultaneous variations in several different parameters to optimize the switching performance of semiconductor devices. As a relatively new device, the SiC MOSFET shines in the field of high power density and high-frequency switching; it has become a popular solution for electric vehicles and renewable energy conversion systems. However, the increase in voltage and current slope caused by high switching speeds inevitably increases the overshoot and oscillation in a circuit and can even generate additional losses. The principle of this new control strategy is to change the voltage and current in the turn-on and turn-off stages by changing the gate driver’s voltage. That is, we reduced the drive’s voltage after a certain time delay and maintained it for a period of time, thus directly controlling the slopes of di/dt and dv/dt. This study focused on the optimization of the SiC MOSFET by changing the time delay preceding the decrease in the voltage of the gate driver, analyzing and calculating the optimal time delay before the decrease in the voltage of the gate driver, and verifying the findings using LTspice simulation software. The simulated results were compared and analyzed with hard-switching strategies. The results showed that the proposed OSS can improve the switching performance of SiC MOSFETs.