Fast Switching Research Articles

Camphor-Based CVD Graphene Integrating CsPbBr3 Quantum Dots for High-Temperature Endurance, High Flexibility, and Fast Optical Switch Photodetection

Photodetectors (PDs) based on camphor-based CVD graphene integrating CsPbBr3 quantum dots (QDs) have been fabricated on mica substrates successfully, showing temperature resistant, foldable, and fast response properties. The graphene synthesized from eco-friendly camphor was transferred onto mica substrates, and then the CsPbBr3 QDs were coated onto the graphene surface to form CsPbBr3 QDs/graphene composition on a flexible mica substrate. According to the Raman spectrum, the structure of camphor-based CVD graphene is multilayer. The photoresponse of CsPbBr3 QDs/graphene composition was revealed by temperature-dependent (ranging from 300 K to 523 K) I-V measurements with/without white light illumination (light intensity: 112 mW/cm2). To highlight the temperature resistance of PDs based on CsPbBr3 QDs/graphene composition, a photo-to-dark current ratio (PDCR) of at 5 V is estimated at different temperatures. The PDCR of the CsPbBr3 QDs/graphene composition-based PD decreased from 3.2 to 0.74 with increasing temperature from 300 K to 523 K. Moreover, after 0 to 300 bending cycles, the vibration of PDCR value at 5 V is small (from 4.3 to 3.7), showing the high flexibility of the CsPbBr3 QDs/graphene composition-based PD. Furthermore, we found that the rise and fall times of the CsPbBr3 QDs/graphene composition-based PDs when we switched the illumination source ON and OFF are ~ 2 and ~1 ms, respectively, indicating fast optical switch behavior. In this study, camphor-based CVD graphene incorporating CsPbBr3 QDs composition-based PD is demonstrated to exhibit high-temperature resistance, high flexibility, and fast response photodetection.Keywords: Camphor, graphene, CsPbBr3 quantum dots, flexible photodetectors

Aligned Semiconducting Carbon Nanotubes for Commercial Logic and RF Electronics

Carbon nanotubes are exceptional semiconductors that offer larger current densities and faster switching than conventional Si and GaAs devices, making nanotubes promising for meeting the performance and energy efficiency needs of next-generation electronics. However, the successful commercialization of carbon nanotubes necessitates the control over semiconducting purity, alignment, packing density, and scalability. The simultaneous control of these characteristics has been a major challenge preventing the integration of nanotubes in industrial electronics and the full exploitation of their electronic properties. This talk will present an overview of recent technological developments and methods that progress towards these goals.In these methods, semiconducting (purity of >99.99%) carbon nanotubes are deposited on target substrates via scalable alignment methods at room temperatures. These individual methods separately enable the deposition of quasi-aligned (±28°) nanotube arrays (~50 nanotubes µm-1) demonstrated across 100 mm substrates, highly-aligned (±6°) nanotube arrays (~100 nanotubes µm-1) demonstrated across 100 mm substrates, and the selective-area deposition of highly-aligned nanotube (±7°) arrays (~up to 250 nanotubes µm-1). The nanotube arrays with high packing density (~250 nanotubes μm-1) yield exceptional current densities of 2 mA μm-1 and transconductances of 1 mS μm-1 at VD of -0.6V. Importantly, due to the low-temperature nature of the deposition processes, these techniques offer a direct path towards the alignment of carbon nanotubes directly on Si and other materials, such as GaN or plastics, to enable high-performance 3D integrated circuits.

Research on characteristics of radio interference of MMC-HVDC lines

Abstract Previous research on radio interference in DC lines has focused on radio interference caused by corona discharge. But with the development of Modular Multilevel Converter Based High Voltage Direct Current (MMC-HVDC) systems, high frequency signals generated by fast switching of Insulate-Gate Bipolar Transistor (IGBT) are transmitted to Direct Current (DC) lines and radiate radio interference outward. On the one hand, the radio interference formula recommended by the dual-level DC transmission line recommended by International Special Committee on Radio Interference (CISPR) is calculated by the radio interference generated by the line corona discharge; On the other hand, by establishing a MMC-HVDC line model, analyse the high frequency signal transmission generated by the fast switching of IGBT in the Modular Multilevel Converter (MMC) to the radio interference generated by radiating outside the DC line. The results of the study show that the radio interference generated by high -frequency signals of IGBT fast switching will decrease with the length of the line. The radio interference value generated by corona discharge is 47.43 dB(μV/m), the radio interference generated by the high-frequency signal of IGBT fast switching is 40.83 dB(μV/m), which is too small than the radio interference of corona discharge.

Dynamic multicolor electrochromic skin in high-brightness flexible WO3/Au asymmetric Fabry–Perot nanocavity fabricated on Nylon 66 porous substrate

Recently, the Fabry–Perot (F–P) cavity electrochromic devices, which are constructed by combining nano-size inorganic electrochromic material WO3 and reflective metal layers, have attracted considerable attention due to their potentials in the fields of dynamic multicolor displays and active camouflage. However, in the few studies that have been reported, the peak reflectance of flexible F–P cavity multicolor electrochromic devices in the visible wavelength band is generally lower than 30 %, which limits their reflective display and camouflage effects in high-brightness environments. Thus, we have combined multicolor reflective electrochromic electrodes in WO3/Au asymmetric F–P nanocavity constructed by magnetron sputtering on a Nylon 66 porous substrate with a highly transparent UV-cured gel electrolyte and a PET plastic sealing procedure. As a result, a flexible and dynamic multicolor electrochromic skin with high reflectance (Rmax＞50 %) and excellent flexibility (bending radius of 4 mm) has been fabricated. The WO3 electrochromic layer at the top works as the dynamic dielectric layer in the broadband absorption Fabry–Perot cavity, and the inert metal Au layer at the bottom works as the reflective layer. The WO3/Au asymmetric F–P cavity can acutely capture the variation in optical constants of WO3 due to the thickness change and electric-driven effects. This cavity facilitates the selective reflection and absorption of the energy distribution of the spectrum after the induced interferometric resonance. As a result, the cavity exhibits a rich array of structural colors, including ocher, taupe, yellow, orange, green, and violet. The electrochromic skin exhibits a fast switching time and maintains 99.43 % of the optical modulation amplitude (ΔR) after 110 coloring/bleaching cycles. It provides a potential option in the field of flexible high-brightness reflective displays and dynamic camouflage in the future.

Adjustable optoelectronic properties of triphenylamine-ethylenedioxythiophene based hybrid electrochromic polymer with different electron-donating substituents

Due to the good optoelectronic properties of triphenylamine (TPA) and its derivatives-based organic conjugated polymers, they have been widely used in various organic electronic devices. They are easy to lose electrons to form stable cationic free radicals with color change under electrochemical oxidation conditions. Therefore, TPA derivatives-based electrochromism materials have attracted the widely attentions of researchers. In this work, a series of TPA derivatives were successfully obtained by Stille coupling reactions, and their basic optical and electrical properties were investigated in detail. Their corresponding polymer films (P(TPA-EDOT), P(PhTPA-EDOT), and P(OCH3TPA-EDOT)) were also prepared on transparent ITO glass by electrodeposition method and their electrochromic properties were further studied. Due to the relatively strong electron donating ability of OCH3– group on the TPA unit, the intramolecular charge transfer peak of OCH3TPA-EDOT is obvious red-shifted and its initial oxidation potential is relatively low, which is beneficial for it to get high-quality electrochromic polymers. Electrochemical analysis shows that all these three polymer films show reversible redox reaction with excellent redox stability. Spectroelectrochemistry shows that all of them have good electrochromic properties and show multi-electrochromic behavior with strong color change. The dynamic study show that all these three polymers have relatively fast switching time (as low as 0.8 s), high coloration efficiency (up to 206.2 C−1 cm2) and obvious optical contrast change. Especially in the near infrared region, the optical contrast is relatively high (P(TPA-EDOT) is 45.3 % at 1100 nm, P(PPhTPA-EDOT) is 53.1 % at 1100 nm, and P(OCH3TPA-EDOT) is 57.2 % at 1100 nm). All these results show that the different substituents on the TPA unit have a certain influence on the resultant monomers’ optoelectronic performances, and they also can adjust the optical band gap of the corresponding polymers with different electrochromic properties.

An FEM Study on Minimizing Electrostatic Cross-Talk in a Comb Drive Micro Mirror Array.

We are developing a phase-modulating micro mirror-array spatial light modulator to be used for real holography within the EU-funded project REALHOLO, featuring millions of pixels that can be individually positioned in a piston mode at a large frame rate. We found earlier that an electrostatic comb-drive array offers the best performance for the actuators: sufficient yoke forces for fast switching even at low voltages compatible with the CMOS addressing backplane. In our first design, the well-known electrostatic cross-talk issue had already been much smaller than would have been possible for parallel-plate actuators, but it was still larger than the precision requirements for high-image-quality holography. In this paper, we report on our analysis of the crucial regions for the electrostatic cross-talk and ways to reduce it while observing manufacturing constraints as well as avoiding excessively high field strengths that might lead to electrical breakdown. Finally, we present a solution that, in FEM simulations, reduces the remaining cross-talk to well below the required specification limit. This solution can be manufactured without any additional processing steps and suffers only a very small reduction of the yoke forces.

Interval observer design for unobservable switched nonlinear partial differential equation systems and its application

SummaryThis paper designs an interval observer for switched nonlinear partial differential equation (PDE) systems. Initially, persistent dwell‐time switching rules are used to model switched PDE systems with fast and slow switching phenomena. Next, for unobservable systems caused by uncertainties, the interval observer for the target PDE systems is proposed by utilizing unknown but bounded information of the initial states, boundary conditions, external disturbances, and measurement noises. Subsequently, by utilizing the estimated state's upper and lower bounds, an interval observer‐based control strategy is devised to stabilize the studied systems, and sufficient conditions to ensure the stability of the target systems and the observation error dynamics are provided. Furthermore, the designed interval observer is employed to detect sensor failures in the presence of various uncertainties. Finally, two examples, including the lithium‐ion battery's temperature estimation and fault detection, are utilized to demonstrate the effectiveness of the obtained methods.

Performance Evaluation of an EI&CI Dual Ionization TOFMS Hyphenated with a Flow Modulated GC×GC System.

The use and compatibility of a dual-ionization TOFMS operating an EI source and a CI source in parallel using a single TOF mass analyzer with flow modulated two-dimensional GC (GC×GC) is described. Important figures of merit of the mass spectrometer that are required for two-dimensional GC hyphenation such as acquisition speed, ion source response, EI/CI switching, the GC transfer, and data alignment are carefully investigated and addressed. Improved fast switching ion optics allow switching in a 100 Hz frequency between EI and CI spectra sampled from the same GC×GC effluent. The spectra quality also influenced by the preseparation, especially of the EI source, is compared to a standard setup operating a single quadrupole MS coupled to the same GC system. Further, two setups including and excluding an additional flame ionization detector are presented. High increments in CI sensitivities are achieved by utilizing the high pumping efficiencies of the CI stage of the used mass spectrometer. By leading high flow ratios of the GC×GC modulation flows toward the CI source, the intensity can be increased by factors of up to 37 while maintaining the pressure balance of the less robust EI source. Finally, thermal desorption GC×GC-EI&CI-TOFMS analyses of traffic emission samples from a federal highway in Germany are executed with the presented setup.

Dynamic multicolour tuning in π-conjugated polymers towards flexible electrochromic displays

Multicolour electrochromic materials have been considered as a promising alternative to achieve dynamic full-colour tuning towards next-generation electronic display technology. However, the development of electrochromics with wide colour gamut and subtle multicolour tunability still remains challenging due to inflexible energy level structures in intrinsic active materials. Herein, the electrochromic π-conjugated polymers with rich and subtle colour tunability were designed and developed based on a fine adjustment on the energy level structures. The chromatic transition covers almost full-colour gamut, and each colour scheme has a rich variety of categories stemming from versatile hues, chromas and lightnesses. Moreover, the multicolour π-conjugated polymers also demonstrate superior overall electrochromic performance, including fast switching (∼1.0 s), high colouration efficiency (160.4 cm2 C−1@550 nm) and good reversibility (over 90 % retention after 10,000 cycles). As a proof of concept, ultrathin and flexible prototype devices are developed by utilizing the multicolour π-conjugated polymers as electrochromic active layer, exhibiting a wide colour gamut and highly saturated multicolour tunability. The design principles proposed in this work may also be applicable to diverse optoelectronic applications.

Multicolor V2O5/TiO2 electrochromic films with fast switching and long lifespan for camouflage and information display

Multicolor V2O5/TiO2 electrochromic films with fast switching and long lifespan for camouflage and information display

Fast polarization switching of undulator radiation up to kilohertz with magnetic field modulation

The fast polarization switching of undulator radiation has attracted more and more attention in recent years. In this paper, a new method is proposed for fast polarization switching of undulator radiation by using magnetic field modulation generated from low-current electromagnetic coils. The key point is that we propose to use the coils with a period length of an integral multiple of the undulator period, which can significantly reduce the required coil field. Through fast switching the power of coils, the radiation spectra of two undulators can be rapidly shifted into and out of the bandpass of a monochromator, enabling fast polarization switching for the user beamline. Based on this advantage, this method has strong potential to be implemented in a storage ring and a high switching frequency up to kilohertz can be expected. Published by the American Physical Society 2024

Design and Implementation of a 2-input Arithmetic and Logic Unit using Quantum-dot Cellular Automata

Quantum-Dot-Cellular Automata (QCA), an emerging nanotechnology rooted in Coulomb repulsion, holds the ability to supplant orthodox complementary metal-oxide semiconductor (CMOS) technology. Its distinctive advantages lie in ultra-low power consumption, fast switching speed, and high-density structures. This study conducts an extensive literature review to introduce an Arithmetic and Logic Unit (ALU) based on QCA principles. The proposed QCA-based ALU incorporates fundamental logic gates, adders, and subtractors, leveraging the latest XOR gate. Utilizing simulation via QCA Designer 2.0.3, an in-depth performance evaluation of the model is conducted, comparing it with established ALUs based on metrics encompassing cell count, delay, and area. The findings showcase the efficiency of the proposed ALU, characterized by its minimal requirement of 277 cells, an area occupancy of 0.43 µm², and a delay of 2.75 clock cycles. This outcome highlights the favorable attributes of our design compared to existing alternatives, suggesting its potential contribution to the advancement of QCA-based digital circuitry. DUJASE Vol. 8 (1) 26-31, 2023 (January)

Laser-Induced Synthesis of Tin Sulfides.

Various polytypes of van der Waals (vdW) materials can be formed by sulfur and tin, which exhibit distinctive and complementary electronic properties. Hence, these materials are attractive candidates for the design of multifunctional devices. This work demonstrates direct selective growth of tin sulfides by laser irradiation. A 532nm continuous wave laser is used to synthesize centimeter-scale tin sulfide tracks from single source precursor tin(II) o-ethylxanthate under ambient conditions. Modulation of laser irradiation conditions enables tuning of the dominant phase of tin sulfide as well as SnS2/SnS heterostructures formation. An in-depth investigation of the morphological, structural, and compositional characteristics of the laser-synthesized tin sulfide microstructures is reported. Furthermore, laser-synthesized tin sulfides photodetectors show broad spectral response with relatively high photoresponsivity up to 4 AW-1 and fast switching time (τ rise = 1.8ms and τ fall = 16ms). This approach is versatile and can be exploited in various fields such as energy conversion and storage, catalysis, chemical sensors, and optoelectronics.

Self-powered electrochromic smart window helps net-zero energy buildings

Net-zero energy buildings are becoming an important energy-saving and low-carbon technology for global environmental protection and resource conservation. As the least energy-efficient building components, windows have promoted the development of electrochemically light/thermal management, where smart windows without external electrical supplies are highly desired for net-zero energy buildings. Here, we develop a self-powered electrochromic smart window system to regulate solar radiation transmittance, constructed by a triboelectric nanogenerator (TENG) and a high-performance electrochromic device. The visible–near-infrared (VIS-NIR) dual-band electrochromic device is well-designed based on an eco-friendly low-energy demand phenothiazine redox ionic liquid, demonstrating a fast switching response of ﹤1.9 s, a large transmittance modulation of >51.8 %, and outstanding electrochemical durability (5.5 % attenuation after 4000 cycles). Upon continuous pressing/releasing motions, the integrated TENG-powered electrochromic smart window (TECSW) displays a prompt light/thermal management behavior with desirable privacy preservation performance (transmittance modulation of 51 % in the visible region) and excellent thermal management property (12.3 °C reducti°n). The whole-building energy simulations show that TECSW can save 347.79 MJ/m2yr (amounting to 96.60 kWh/m2yr) of operational Heating Ventilation Air Conditioning (HVAC) warming/cooling energy consumption among 34 cities in China, accounting for 17.25 % of the total energy consumption. This research provides new insight into designing green and energy-efficient smart windows for net-zero energy buildings.

On-demand transposition across light-matter interaction regimes in bosonic cQED

The diverse applications of light-matter interactions in science and technology stem from the qualitatively distinct ways these interactions manifest, prompting the development of physical platforms that can interchange between regimes on demand. Bosonic cQED employs the light field of high-Q superconducting cavities coupled to nonlinear circuit elements, harnessing the rich dynamics of their interaction for quantum information processing. However, implementing fast switching of the interaction regime without deteriorating the cavity coherence is a significant challenge. We present an experiment that achieves this feat, combining nanosecond-scale frequency tunability of a transmon coupled to a cavity with lifetime of hundreds of microseconds. Our implementation affords a range of useful capabilities for quantum information processing; from fast creation of cavity Fock states using resonant interaction and interchanging tomography techniques at qualitatively distinct interaction regimes on the fly, to the suppression of unwanted cavity-transmon dynamics during idle evolution. By bringing flux tunability into the bosonic cQED toolkit, our work opens up the possibility to probe the full range of light-matter interaction dynamics within a single platform and provides valuable pathways towards robust and versatile quantum information processing.

Stable chalcogenide Ge–Sb–Te heterostructures with minimal Ge segregation

Matching of various chalcogenide films shows the advantage of delivering multilayer heterostructures whose physical properties can be tuned with respect to the ones of the constituent single films. In this work, (Ge–Sb–Te)-based heterostructures were deposited by radio frequency sputtering on Si(100) substrates and annealed up to 400 °C. The as-deposited and annealed samples were studied by means of X-ray fluorescence, X-ray diffraction, scanning transmission electron microscopy, electron energy loss spectroscopy and Raman spectroscopy. The heterostructures, combining thermally stable thin layers (i. e. Ge-rich Ge5.5Sb2Te5, Ge) and films exhibiting fast switching dynamics (i. e. Sb2Te3), show, on the one side, higher crystallization-onset temperatures than the standard Ge2Sb2Te5 alloy and, on the other side, none to minimal Ge-segregation.

Engineering of TiN/ZnO/SnO2/ZnO/Pt multilayer memristor with advanced electronic synapses and analog switching for neuromorphic computing

The two-terminal memristor is a promising neuromorphic artificial electronic device, mirroring biological synapses in structure and replicating various synaptic functions. Despite its advantages, challenges in achieving high reliability, gradual switching, and low energy consumption hinder progress in neuromorphic devices. This study explores electronic synapses and simulates analog switching in a Pt/TiN/ZnO/SnO2/ZnO/Pt multilayer (ML) configuration, featuring a ∼3 nm SnO2 layer between ZnO layers. Results show enhanced cycling endurance (more than 250 cycles), resistance window (102), tunable synaptic plasticity, and multilevel switching. ML memristors exhibit low coefficient of variation (4.5 %) in set voltage, low energy consumption (set = ∼0.12 nj, reset = ∼0.1 nj), and fast switching speeds (set = 300 ns, reset = 200 ns), suitable for high-density memory and neuromorphic systems. They successfully emulate synaptic functions, including paired-pulse facilitation (PPF), spike voltage-dependent plasticity (SVDP), spike width-dependent plasticity (SWDP), spike frequency-dependent plasticity (SFDP), and post-tetanic potentiation (PTP). Modulating pulse amplitude and width achieves multilevel conductance in long-term potentiation (LTP) and long-term depression (LTD). Using nonlinear conductance data, a 96.5 % image pattern recognition accuracy is achieved in a deconvolution neural network (DNN) simulation. These results highlight the ML memristor's potential in efficient neuromorphic computing systems.

Travelling waves in a minimal go-or-grow model of cell invasion

We consider a minimal go-or-grow model of cell invasion, whereby cells can either proliferate, following logistic growth, or move, via linear diffusion, and phenotypic switching between these two states is density-dependent. Formal analysis in the fast switching regime shows that the total cell density in the two-population go-or-grow model can be described in terms of a single reaction–diffusion equation with density-dependent diffusion and proliferation. Using the connection to single-population models, we study travelling wave solutions, showing that the wave speed in the go-or-grow model is always bounded by the wave speed corresponding to the well-known Fisher–KPP equation.

A nanoscale photonic thermal transistor for sub-second heat flow switching

Control of heat flow is critical for thermal logic devices and thermal management and has been explored theoretically. However, experimental progress on active control of heat flow has been limited. Here, we describe a nanoscale radiative thermal transistor that comprises of a hot source and a cold drain (both are ~250 nm-thick silicon nitride membranes), which are analogous to the source and drain electrodes of a transistor. The source and drain are in close proximity to a vanadium oxide (VOx)-based planar gate electrode, whose dielectric properties can be adjusted by changing its temperature. We demonstrate that when the gate is located close ( < ~1 µm) to the source-drain device and undergoes a metal-insulator transition, the radiative heat transfer between the source and drain can be changed by a factor of three. More importantly, our nanomembrane-based thermal transistor features fast switching times ( ~ 500 ms as opposed to minutes for past three-terminal thermal transistors) due to its small thermal mass. Our experiments are supported by detailed calculations that highlight the mechanism of thermal modulation. We anticipate that the advances reported here will open new opportunities for designing thermal circuits or thermal logic devices for advanced thermal management.

Highly luminescent, fast switching electro-optical device based on core-shell bimetallic nanoparticles/ ferroelectric liquid crystal composites.

Owing to the passive nature of liquid crystal (LC) materials, achieving luminous displays using pure LC materials is challenging. In addition, it is difficult to achieve a fast switching time using pristine ferroelectric LC devices without compromising their cell thickness. Herein, we have developed a fast switching and highly luminescent electro-optical device by dispersing a minute concentration of bimetallic nanoparticles (Au@Ag NPs) having a spherical gold core and a silver shell within a ferroelectric liquid crystal (FLC) host matrix, ZLI3654. Au@Ag core-shell NPs having synergic attributes of both counterparts were successfully synthesized by a facile seed-mediated route. The Au core helps to tune the shape of the Ag shell and provides enhanced electron density as well as improved stability against oxidation. Introducing nanoparticles induces little structural modifications to the host FLC, resulting in an improvement in the mesogenic alignment. Interestingly, ∼29-fold enhancement in the photoluminescence (PL) intensity is observed on dispersing 0.25 wt% of Au@Ag NPs into the FLC host matrix. The enhanced electromagnetic field in the FLC-nanocomposite is attributed to the Localized Surface Plasmon Resonance of Au@Ag NPs, which strengthens the photon absorption rates by the FLC molecules, culminating in the massive enrichment of the PL intensity. In addition, the improved localized electric field inside the FLC device led to a noticeable enhancement in the spontaneous polarization, dielectric permittivity, and, most interestingly, ∼53% fastening in the switching time at an optimum concentration (0.25 wt%) of Au@Ag NPs. The improved electro-optical parameters of the Au@Ag NPs/FLC composite have been compared with the performance of both pristine Au NPs/FLC and Ag NPs/FLC composites, respectively, for the comprehensiveness of the study. The present study paves a systematic way to develop FLC-based advanced electro-optical devices with faster switching and higher luminescence properties.