Multiple Switching Cycles Research Articles

Engineering Band Gap of Ternary Ag2TexS1−x Quantum Dots for Solution-Processed Near-Infrared Photodetectors

Silver-based chalcogenide semiconductors exhibit low toxicity and near-infrared optical properties and are therefore extensively employed in the field of solar cells, photodetectors, and biological probes. Here, we report a facile mixture precursor hot-injection colloidal route to prepare Ag2TexS1−x ternary quantum dots (QDs) with tunable photoluminescence (PL) emissions from 950 nm to 1600 nm via alloying band gap engineering. As a proof-of-concept application, the Ag2TexS1−x QDs-based near-infrared photodetector (PD) was fabricated via solution-processes to explore their photoelectric properties. The ICP-OES results reveal the relationship between the compositions of the precursor and the samples, which is consistent with Vegard’s equation. Alloying broadened the absorption spectrum and narrowed the band gap of the Ag2S QDs. The UPS results demonstrate the energy band alignment of the Ag2Te0.53S0.47 QDs. The solution-processed Ag2TexS1−x QD-based PD exhibited a photoresponse to 1350 nm illumination. With an applied voltage of 0.5 V, the specific detectivity is 0.91 × 1010 Jones and the responsivity is 0.48 mA/W. The PD maintained a stable response under multiple optical switching cycles, with a rise time of 2.11 s and a fall time of 1.04 s, which indicate excellent optoelectronic performance.

Monitoring Chip Branch Failure in Multichip IGBT Modules Based on Gate Charge

The reliability of the multichip insulated gate bipolar transistor (IGBT) modules has been a concern. Condition monitoring is an effective approach to enhance reliability and improve the quality of customer service. This paper proposes a method for monitoring the chip branch failure due to bond wires fatigue in the multichip IGBT modules. The idea is based on the cumulative effect of the gate charge deviation when the chip branch fails. By integrating the turn-on gate current of multiple switching cycles, the health state of multichip IGBT modules is characterized by the capacitor voltage as a health-sensitive parameter that can be extracted in the proposed monitoring circuit integrated into the gate driver. The capacitor voltage decreases significantly when the chip branch occurs due to bond wires fatigue. It is stable during sampling and has a strong immunity to junction temperature, collector current, and collector-emitter voltage. Besides, the method is non-intrusive and has the potential for real-time and online monitoring. These characteristics make the method reliable, easy to implement, and convenient for health status identification. The confirmatory experiment is carried out to verify the feasibility of the method.

Condition for Suppressing Subharmonic Oscillation in Digital Peak Current-Mode Multi-Cycle Controlled Converters

Peak current-mode control is a control algorithm for switched-mode power supplies (SMPSs) that is characterized by high-speed response and high-stability. Currently, a method of implementing peak current-mode control in a digital controller has been proposed however, there is a limit to increasing the switching frequency. Therefore, in a previous study, we proposed a method that enables high-frequency switching by applying a control method called multi-cycle control, which applies the same ON duty ratio over multiple switching cycles to the existing method. Furthermore, in peak current-mode control, an unstable phenomenon called subharmonic oscillation occurs, which is problematic. Generally, this problem is solved by slope compensation however, it cannot be applied to multi-cycle control. Therefore, in previous work, we derived the condition to suppress subharmonic oscillation by designing parameters of multi-cycle control. In this study, we verified the above-mentioned conditions using a real-circuit.

In-situ growth all-inorganic bismuth-based perovskite single crystal hexagonal sheets for planar photodetector

Single crystal thin films can achieve the balance between thickness and mobility, which is widely used in the field of optoelectronic devices. Herein, lead-free perovskite Cs3Bi2I9 single crystal hexagonal sheets with preferred orientation along (002) were prepared by solution method. The Bi element is positively trivalent without oxidation in the single crystal hexagonal sheets. The growth processes of Cs3Bi2I9 crystal including nucleation and crystal growth are revealed by in-situ optical and structural observation. The Cs3Bi2I9 single crystal hexagonal sheets demonstrate excellent stability without encapsulation during long time exposure to the air. Obvious fluorescence quenching effect observed by steady-state and time-resolved photoluminescence measurement indicates charge transfer from Cs3Bi2I9 to ITO electrodes. Planar photodetectors based on Cs3Bi2I9 exhibit good photosensitive property, reproducibility and stability during multiple switching cycles. This work is conducive to lead-free perovskite regulation and further applications in photoelectronic devices.

3-D Physical Electro-Thermal Modeling of Nanoscale Y2O3 Memristors for Synaptic Application

Here, we report the physical electro-thermal modeling of nanoscale Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -based memristor devices. The simulation is carried out by the combined software package of COMSOL Multiphysics and MATLAB. The presented physical modeling is based on the minimization of free energy at an applied voltage. The simulated results exhibit a stable pinched hysteresis loop in resistive switching (RS) response in multiple switching cycles. The RS responses show low values of coefficient of variability ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{V}$ </tex-math></inline-formula> ), i.e., 17.36% and 17.09% in SET and RESET voltages, respectively, during cycle-to-cycle variation. The impact of voltage ramp rate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{RR}$ </tex-math></inline-formula> ) on the device characteristics such as switching response and synaptic plasticity behavior of the device is investigated. The simulated outcomes significantly depict the impact of oxide layer thickness on the switching voltages in the nanoscale device.

Role of an oxide interface in a resistive switch

In the present era of data-driven architectures like 5G, Internet of things (IoT), Artificial Intelligence (AI), etc, the requirement of fast-switchable memory storage is more than ever. Oxide resistive switches are considered to be a primary choice in the non-volatile memory design. In this work, we have engineered the conventional metal-insulator-metal (MIM) structure of an oxide memristor (Ag/ZnO/ITO) by inducing an additional oxide layer La0.7Sr0.3MnO3 (LSMO) at the interface between the active layer (ZnO) and Ag electrode. The presence of LSMO acts as a reservoir for the oxygen vacancies, easing the conducting filament formation process in ZnO, thereby enabling drastic improvement of the switching performance and offering reliable endurance over multiple switching cycles. First-principles-based calculations suggested the role of oxygen vacancies in controlling the electronic state of ZnO and formation of vacancies in the resistive switching process, which is in agreement with the experimental observation. The current results pave ways for improving the switching performance of resistive memory circuits through simple structural engineering incorporation, which lies at the heart of oxide electronics.

Rewritable color nanoprints in antimony trisulfide films.

Materials that exhibit large and rapid switching of their optical properties in the visible spectrum hold the key to color-changing devices. Antimony trisulfide (Sb2S3) is a chalcogenide material that exhibits large refractive index changes of ~1 between crystalline and amorphous states. However, little is known about its ability to endure multiple switching cycles, its capacity for recording high-resolution patterns, nor the optical properties of the crystallized state. Unexpectedly, we show that crystalline Sb2S3 films that are just 20 nm thick can produce substantial birefringent phase retardation. We also report a high-speed rewritable patterning approach at subdiffraction resolutions (>40,000 dpi) using 780-nm femtosecond laser pulses. Partial reamorphization is demonstrated and then used to write and erase multiple microscale color images with a wide range of colors over a ~120-nm band in the visible spectrum. These solid-state, rapid-switching, and ultrahigh-resolution color-changing devices could find applications in nonvolatile ultrathin displays.

Reversible optical tuning of GeSbTe phase-change metasurface spectral filters for mid-wave infrared imaging.

Tunable narrowband spectral filtering across arbitrary optical wavebands is highly desirable in a plethora of applications, from chemical sensing and hyperspectral imaging to infrared astronomy. Yet, the ability to reconfigure the optical properties, with full reversibility, of a solid-state large-area narrowband filter remains elusive. Existing solutions require either moving parts, have slow response times, or provide limited spectral coverage. Here, we demonstrate a 1-inch diameter continuously tunable, fully reversible, all-solid-state, narrowband phase-change metasurface filter based on a GeSbTe-225 (GST)-embedded plasmonic nanohole array. The passband of the presented device is with transmittance and operates across the 3–5 µm thermal imaging waveband. Continuous, reconfigurable tuning is achieved by exploiting intermediate GST phases via optical switching with a single nanosecond laser pulse, and material stability is verified through multiple switching cycles. We further demonstrate multispectral thermal imaging in the mid-wave infrared using our active phase-change metasurfaces. Our results pave the way for highly functional, reduced power, compact hyperspectral imaging systems and customizable optical filters for real-world system integration.

A Memristive Element Based on an Electrically Controlled Single-Molecule Reaction.

The exponential proliferation of data during the information age has required the continuous exploration of novel storage paradigms, materials, and devices with increasing data density. As a step toward the ultimate limits in data density, the development of an electrically controllable single-molecule memristive element is reported. In this device, digital information is encoded through switching between two isomer states by applying a voltage signal to the molecular junction, and the information is read out by monitoring the electrical conductance of each isomer. The two states are cycled using an electrically controllable local-heating mechanism for the forward reaction and catalyzed by a single charge-transfer process for the reverse switching. This single-molecule device can be modulated in situ, is fully reversible, and does not display stochastic switching. The I-V curves of this single-molecule system also exhibit memristive character. These features suggest a new approach for the development of molecular switching systems and storage-class memories.

Memristors Based on Poly(p-xylylene) with Embedded Silver Nanoparticles

The properties of memristors based on poly(p-xylylene) with embedded silver nanoparticles have been studied, including current–voltage characteristics, resistive switching phenomenon, stability with respect to multiple switching cycles, and ability to store the resistive state in time. It is established that the incorporation of silver nanoparticles into polymer matrix significantly improves the main characteristics of memristors. The obtained results can be used for the creation of large memristor arrays with homogeneous characteristics capable of emulating synapses in neuromorphic computing systems.

Dynamic on-Resistance in GaN-on-Si HEMTs: Origins, Dependencies, and Future Characterization Frameworks

Gallium nitride high-electron-mobility transistors (GaN HEMTs) exhibit dynamic ON-resistance (dR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> ), where the ON-resistance immediately after turn-ON is higher than the dc value at the same junction temperature. A proliferation of recent literature reportsdR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> , with some publishing an eight times increase in conduction losses and others finding that the problem is nonexistent. This variation can be largely attributed to the standardized double-pulse-test (DPT) method, which does not specify the blocking time and will ignore any effects that accumulate over multiple switching cycles. With no consistent measurements, designers are left without an accurate conduction loss estimate in converters with GaN HEMTs. We discuss the underlying causes of charge trapping to find the key influences over dR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> , and show that the DPT technique gives invalid results. Our measurements validate that each operating parameter must be independently controlled and that only steady-state dR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> measurements will predict in situ performance. For the commercial GaN HEMT tested in this letter, the worst-case dR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> is nearly two times higher than the dc resistance at the same temperature, confirming that accurate dR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> characterization remains critical to predicting converter characteristics. Finally, we provide a reporting framework for GaN HEMT manufacturers and methods to estimate conduction losses in converters with GaN HEMTs.

Temporal and Reversible Control of a DNAzyme by Orthogonal Photoswitching.

The reversible switching of catalytic systems capable of performing complex DNA computing operations using the temporal control of two orthogonal photoswitches is described. Two distinct photoresponsive molecules have been separately incorporated into a split horseradish peroxidase-mimicking DNAzyme. We show that its catalytic function can be turned on and off reversibly upon irradiation with specific wavelengths of light. The system responds orthogonally to a selection of irradiation wavelengths and durations of irradiation. Furthermore, the DNAzyme exhibits reversible switching and retains this ability throughout multiple switching cycles. We apply our system as a light-controlled 4:2 multiplexer. Orthogonally photoswitchable DNAzyme-based catalysts as introduced here have potential use for controlling complex logical operations and for future applications in DNA nanodevices.

Probabilistic insight to possibility of new metal filament nucleation during repeated cycling of conducting bridge memory

The question of whether resistance switching in conducting bridge random access memory (CBRAM) devices occurs through a single filament which repeatedly undergoes nucleation and rupture or through different filaments for different cycles is difficult to ascertain using conventional electrical tests on metal–insulator–metal (MIM) capacitor structures. In order to profile the spatial location of the conductive filament during multiple switching cycles, we make use of the Ni–HfO2–Si based metal–insulator–semiconductor (MIS) stack with a transistor test structure so that the lateral location of the filament along the source to drain can be probed electrically by considering the weighted ratio of source and drain currents measured. Our analysis reveals that filaments can evolve in spatially uncorrelated locations and switching is not always caused by the same filament over and over again. A simple statistical model is also provided to justify the inferences of the electrical study. The probability of a new filament nucleating elsewhere in the dielectric is a strong function of the oxide barrier thickness as well as the curvature radii of the previously ruptured metal filament edges.

A pure single-walled carbon nanotube thin film based three-terminal microelectromechanical switch

The electrical and physical properties of pure single-walled carbon nanotube thin films deposited through a layer-by-layer-self-assembly process are discussed. The film thickness was proportional to the number of dipping cycles. The film resistivity was estimated as 2.19×10−3 Ω cm after thermal treatment processes were performed. The estimated specific contact resistance to gold electrodes was 6.33×10−9 Ω m2 from contact chain measurements. The fabricated three-terminal microelectromechanical switch using these films functioned as a beam for multiple switching cycles with a 4.5 V pull-in voltage. This switch is believed to be a promising device for low power digital logic applications.

Resistive Switching Characteristics and Failure Analysis of TiO2 Thin Film Deposited by RF Magnetron Sputtering System

The effect of the postannealing conditions of thin films deposited using a radio frequency (rf) magnetron sputtering system on their electrical resistive switching characteristics was evaluated in the structure, and the compositional change of the thin films after resistive switching failure was investigated. The structure with polycrystalline showed a relatively more stable set/reset voltage dispersion and resistance difference between the high resistance state (HRS) and low resistance state (LRS) than those with amorphous . In the energy dispersive X-ray spectroscopy analysis of the thin film in with reset-stuck failure, in which the resistive switching from the HRS to the LRS failed after repeated resistive switching, the peak intensity of oxygen was significantly decreased compared with that before resistive switching and the decrease of the oxygen content was more noticeable near the top electrode than near the bottom electrode. Consequently, it is considered that the depletion of oxygen in the thin film after multiple resistive switching cycles by successive voltage sweeping could be one of the main causes of the resistive switching failure phenomenon.

Ferroelectric properties of epitaxial Pb(Zr,Ti)O3 thin films on silicon by control of crystal orientation

Crystalline Pb(Zr,Ti)O3 (PZT) thin films between metallic-oxide SrRuO3 (SRO) electrodes were prepared using pulsed laser deposition on CeO2/yttria-stabilized zirconia buffered silicon (001) substrates. Different deposition conditions for the initial layers of the bottom SRO electrode result in an orientation switch. Either (110)- or (001)-oriented SRO thin films are obtained and the PZT films deposited on the bottom electrode continued both growth directions. The ferroelectric characteristics of the SRO/PZT/SRO capacitors are found to be strongly dependent on their crystalline orientation: PZT (001)-oriented thin films showed stable, high quality ferroelectric response, while the remnant polarization of the PZT (110)-oriented thin films only show high response after multiple switching cycles.

Fatigue of lead titanate and lead zirconate titanate thin films

The fatigue of lead titanate and lead zirconate titanate ferroelectric thin films, i.e., a change in the polarization as a function of the number of switching cycles in an external electric field, is investigated experimentally. The threshold numbers of switching cycles are determined to be 1010–1011 for the lead titanate films and 109–1010 for the lead zirconate titanate films. It is shown that a change in the temperature does not substantially affect the threshold number of switching cycles at which the switched polarization decreases drastically. However, an increase in the external field strength leads to a noticeable decrease in the threshold number of switching cycles. The process of fatigue is accompanied by an increase in the coercive field and the internal bias field. It is established that, as the number of switching cycles increases, the internal bias field changes more significantly as compared to the coercive field. The absence of a change in the phase composition in repeatedly switched samples indicates that the fatigue processes have a nonchemical nature. The anomaly observed in the frequency dependence of the permittivity in the frequency range 106–107 Hz due to the domain structure disappears after multiple switching cycles. This suggests that the observed fatigue phenomenon has a domain nature.

A Three-Terminal Carbon Nanorelay

Three-terminal nanorelay structures were fabricated with multiwall carbon nanotubes (MWNTs). The nanotube relays were deflected by applying a gate voltage until contact (mechanical and/or electrical) was made with a drain electrode, thus closing the circuit. It was possible to achieve multiple switching cycles, showing that carbon nanotubes are suitable and practical systems for developing nanoelectromechanical devices of this kind.

In situ measurements of thickness changes and mechanical stress upon gasochromic switching of thin MoOx films

Thin films of MoOx coated with platinum as a catalyst were prepared by dc magnetron sputtering from a molybdenum target in an oxygen and argon atmosphere. The films were colored and bleached by exposure to diluted hydrogen gas and air, respectively. In situ measurements of x-ray reflectance and substrate curvature were performed during switching cycles. Upon hydrogen exposure a remarkable thickness decrease of 11% and a density increase of 6.5% are observed by x-ray reflectance measurements. Corresponding changes in optical transmittance and mechanical stress up to several hundreds of MPa are also observed. These changes are not fully reversible as revealed by measurements of multiple switching cycles. Both the change of thickness and density, as well as the change of optical transmittance and mechanical stress can be explained by the existence of a mixed phase of edge and corner sharing MoO3 octahedra whereupon the first coloration the ratio between edge and corner sharing octahedra is changed.

Magnetic stability in exchange-spring and exchange-bias systems after multiple switching cycles

We have studied the magnetic stability in exchange-bias and exchange-spring systems during repeated reversal of the pinned layer. The samples were prepared by epitaxial sputter deposition. The exchange-biased system consists of a combination of ferromagnetic and antiferromagnetic Fe/Cr superlattices. The exchange-spring system is a bilayer structure made of hard Sm–Co and soft Fe ferromagnetic layers. The magnetic properties were investigated using the magneto-optic Kerr effect during repeated reversal of the soft layer magnetization by field cycling up to 107 times. The experimentally observed decay behaviors are discussed in terms of microstructure and spin configuration of the pinning layers.