High-speed Devices Research Articles

Reconfigurable skyrmion logic gates with auto-annihilating skyrmion function

Skyrmions are a spin texture with topological protection properties, which can be considered as an excellent candidate for the next generation of high-speed, nonvolatile, and low-power consumption spin devices due to their unique dynamic characteristics. In this work, we propose reconfigurable skyrmion-based logic gates with auto-annihilating skyrmion function, and six logical operations can be implemented in our model relying on the competition among the spin transfer torque (STT), skyrmion Hall effect (SkHE), skyrmion-edge repulsion, skyrmion-skyrmion topological repulsion, and voltage-controlled magnetic anisotropy (VCMA) effect. The influence of temperature on the logical operation processes indicates that the temperature range for achieving all types of logic operations and automatic annihilation function is 0–96 K. The function of automatically clearing skyrmions after the completion of logic operations can free up space for storing unnecessary skyrmions, and save energy consumption for applying additional current to eliminate them. Our results can be beneficial for the design and development of magnetic skyrmion logic gates.

Revealing the ultrafast spontaneous emission in plasmon-enhanced monolayer semiconductor nano-light sources

Nanoscale spontaneous light sources are promising alternatives to lasers for high-speed optical communications and interconnections through energy-efficient integrated circuits. Yet, developing the spontaneous light sources faster than lasers is hampered by the detection means (e.g., time-resolved fluorescence spectroscopy). Here, by coupling monolayer WSe2 to individual plasmonic nanocavities, we achieved an efficient spontaneous light source with potential ultrafast modulation bandwidth and superior brightness. The ultrafast radiative decay rates can be determined and derived solely from the experimental parameters by combining the coupling strength and the photoluminescence enhancement in a single nanocavity-WSe2 hybrid. As a result, the hybrid light source has a radiative lifetime down to 350 fs, indicating a potential modulation bandwidth up to 440 GHz, which is 10 times of the traditional semiconductor lasers. Furthermore, the quantum yield is enhanced by a factor of over 300-folds up to 20.8% through making full use of the highly confined nanocavity mode. The nanocavity-WSe2 hybrid we built provides a promising approach for constructing high-speed light-emitting devices.

Surface topography detection based on an optical differential metasurface.

Surface topography detection can extract critical characteristics from objects, playing an important role in target identification and precision measurement. Here, an optical method with the advantages of low power consumption, high speed, and simple devices is proposed to realize the surface topography detection of low-contrast phase objects. By constructing reflected light paths, a metasurface can perform spatial differential operation via receiving the light directly reflected from a target. Therefore, our scheme is experimentally demonstrated as having remarkable universality, which can be used not only for opaque objects, but also for transparent pure phase objects. It provides a new, to the best of our knowledge, application for optical differential metasurfaces in precise detection of microscale surface topography.

Single-crystallization of electrolytic copper foils

Depending on the production process, copper (Cu) foils can be classified into two types, i.e., rolled copper (r-Cu) foils and electrolytic copper (e-Cu) foils. Owing to their high electrical conductivity and ductility at low cost, e-Cu foils are employed extensively in modern industries and account for more than 98% of the Cu foil market share. However, industrial e-Cu foils have never been single-crystallized due to their high density of grain boundaries, various grain orientations and vast impurities originating from the electrochemical deposition process. Here, we report a methodology of transforming industrial e-Cu foils into single crystals by facet copy from a single-crystal template. Different facets of both low and high indices are successfully produced, and the thickness of the single crystal can reach 500 µm. Crystallographic characterizations directly recognized the single-crystal copy process, confirming the complete assimilation impact from the template. The obtained single-crystal e-Cu foils exhibit remarkably improved ductility (elongation-to-fracture of 105% vs. 25%), fatigue performance (the average numbers of cycles to failure of 1600 vs. 200) and electrical property (electrical conductivity of 102.6% of the international annealed copper standard (IACS) vs. 98.5%) than original ones. This work opens up a new avenue for the preparation of single-crystal e-Cu foils and may expand their applications in high-speed, flexible, and wearable devices.

Experiment and simulation of electron density distribution in discharge plasma at hypersonic speed

Pulsed discharge can generate high density and high dynamic plasma, which has promising application prospects in the field of stealth technology for high-speed aircraft. To study the evolution process of pulsed discharge plasma jet in a hypersonic flow field, the pulsed discharge experiment was performed in a hypersonic wind tunnel with 8 M in this paper. The plasma evolution process and electron density were measured by a high-speed schlieren device and spectrum acquisition system. A shock wave appeared after the blast wave generated by the discharge interacted with the external flow field. In the region below the shock wave, the plasma jet flowed downstream and produced a plasma layer. The electron density of the jet increases with the injected energy, and the peak density reaches 5.28 × 1015 cm−3. Due to the limitations of experimental measurements, based on the Navier–Stokes equations and the air dissociation and ionization model, including 11 components and 20 chemical reactions, a simulation for the experimental process was performed. At the injected energy of 495 and 880 mJ, the difference between the simulated electron density and the experimental value is 16.09% and 15.34%, respectively. The thickness of the plasma layer initially increases and then decreases over time, with higher injected energy leading to a thicker layer. Specifically, when 880 mJ of energy is injected, the plasma layer can reach a maximum thickness of 6.69 cm. The collision frequency fluctuates around 1 GHz, and the collision frequency at the upper edge of the plasma layer is large.

Human Development in the US: An Analysis of the Rich and Poor in NY State

Poverty has a devastating influence on human development, limiting educational access, high speed and efficient technological devices, and health necessities. Initially, economists focused on gains in income as a way to measure progress, such as GDP per capita, and investments in factors of production including land, labor, and capital that can spur such growth. Investments in labor include investments in education, training, and health as a means to promote productivity and therefore income gains. However, there has been a shift in focus to human development, whose objective extends beyond income to improved human capabilities as measured by quality of life, education, and health. Clear trends in the causes and effects of poverty and the impediments to human development have been evaluated globally, but what remains unclear is whether such trends hold at subnational levels. This study therefore seeks to assess one state in the U.S., the state of New York, to determine what factors are associated with disparities in human development by evaluating the differences between the fifty richest and fifty poorest towns. Through inferential hypothesis testing, this research evaluated which measures related to human development and poverty were statistically significantly different for the richest and poorest towns in New York. The two-tailed t-tests revealed significant differences in many factors tested, including health insurance, educational attainment, access to technology, and flood risk. The latter two findings have important policy implications for alleviating impacts of poverty, including closing the digital gap and implementing adaptations in high flood-risk, impoverished communities.

Fringe-to-pulse counting demodulation of a laser interferometer for primary vibration calibration

A high accuracy and real-time amplitude-phase demodulation method based on the pulse counting of optical fringes is proposed for a laser interferometer to realize amplitude and phase measurement of the vibration in primary vibration calibration. The two orthogonally analog signals with high frequency are converted into two digital signals through the comparison module instead of a high-speed data acquisition device. Then one displacement increment during a quarter period of the digital signal can be obtained by the high-frequency clock through comparing the four states of two orthogonally digital signals. The actual output rate of the demodulation data will be decreased by subsample with the vibration frequency. The results of experiment illustrated the deviations were within the limits and the displacement waves were well reconstructed, not only for homodyne interferometer but also for heterodyne interferometer. The proposed method involves less complicated hardware equipment and algorithm, so it is sufficient for real-time and high-precision demodulation of the laser interference signals to realize vibration measurements in primary vibration calibration.

Part I—Advancements in Power Converter Technologies: A Focus on SiC-MOSFET-Based Voltage Source Converters

Power converter technologies have become vital in various applications due to their efficient management of electrical energy. With the growing prominence of renewable energy sources such as solar and wind, the high penetration of power electronic converters has been justified. However, ensuring power quality has emerged as a significant challenge for grid-connected power converters. The divergence from the ideal sinusoidal waveform in terms of magnitude and frequency impacts both grid-side currents and voltages. Several studies have proposed solutions to address power quality issues at the load side. The advancement of power converters has been fueled by the development of high-performance microprocessors and the emergence of high-speed switching devices, such as SiC-MOSFETs. This paper focuses on the design of voltage source converters, particularly those based on SiC-MOSFET semiconductor devices. The article presents the design of H-Bridge cells, discusses two-level voltage source converters based on cascade H-Bridge cells in a parallel configuration with experimental fault analysis, addresses the seven-level voltage source converter topology, and explores the design and experimental results of the matrix converter. The findings underscore the importance of considering the entire converter design for improved performance at high switching frequencies. The article concludes by summarizing the main outcomes and implications of this research.

Reduction of aerosol dissemination in a dental area generated by high-speed and scaler ultrasonic devices employing the "Prime Protector".

The use of an external dome aerosol containment device (Prime Protector) is proposed to reduce the spread of particles within the dental office. Hence, the aim of our study was to compare the spread of bioaerosols generated by a High-speed Handpiece (HH) and an Ultrasonic Prophylaxis Device (UPD), with and without the Prime Protector dome (PP) by counting Colony Forming Units (CFU) of Lactobacillus casei Shirota, at different distances on the x and y axis. The PP was located considering the parallelism between the base of the dome and the frontal plane of the simulator, aligning the center of the mouth with the center of the dome. The PP dome measurements are 560.0mm x 255.0mm x 5mm. Petri dishes were placed at 0.5 m, 1 m and 1.5 m respectively. Aerosol generation in the laboratory environment was done three times with the following experimental groups 1) HH, 2) HH-PP, 3) UPD, 4) UPD-PP. Each dental device activation (HH and UPD) had a time frame of 2 minutes on the upper anterior teeth of the dental phantom with a liquid suspension containing Lactobacillus casei Shirota (YAKULT 0836A 0123; 1027F 0407). Air pressure and ventilation were parameterized. No separate high-volume evacuation used, nor was there any air removal attached to the dome. Results showed no significant difference between distance and axis in the CFU count. When means for devices and distances were compared between each of them all showed significant differences except for UPD and UPD-PP (p <0,004). In conclusion, external devices like Prime Protector could help decrease aerosol diffusion during high-speed handpiece activation. However, this dome does not replace the use of PPE inside dental clinics.

Machine Learning and IoT Trends for Intelligent Prediction of Aircraft Wing Anti-Icing System Temperature

Airplane manufacturers are frequently faced with formidable challenges to improving both aircraft performance and customer safety. Ice accumulation on the wings of aircraft is one of the challenges, which could result in major accidents and a reduction in aerodynamic performance. Anti-icing systems, which use the hot bleed airflow from the engine compressor, are considered one of the most significant solutions utilized in aircraft applications to prevent ice accumulation. In the current study, a novel approach based on machine learning (ML) and the Internet of Things (IoT) is proposed to predict the thermal performance characteristics of a partial span wing anti-icing system constructed using the NACA 23014 airfoil section. To verify the proposed strategy, the obtained results are compared with those obtained using computational ANSYS 2019 software. An artificial neural network (ANN) is used to build a forecasting model of wing temperature based on experimental data and computational fluid dynamics (CFD) data. In addition, the ThingSpeak platform is applied in this article to realize the concept of the IoT, collect the measured data, and publish the data in a private channel. Different performance metrics, namely, mean square error (MSE), maximum relative error (MAE), and absolute variance (R2), are used to evaluate the prediction model. Based on the performance indices, the results prove the efficiency of the proposed approach based on ANN and the IoT in designing a forecasting model to predict the wing temperature compared to the numerical CFD method, which consumes a lot of time and requires high-speed simulation devices. Therefore, it is suggested that the ANN-IoT approach be applied in aviation.

Structural Designs of Transparent Polyimide Films with Low Dielectric Properties and Low Water Absorption: A Review.

The rapid development of communication networks (5G and 6G) that rely on high-speed devices requiring fast and high-quality intra- and inter-terminal signal transmission media has led to a steady increase in the need for high-performance, low-dielectric-constant (Dk) (<2.5) materials. Consequently, low-dielectric polymeric materials, particularly polyimides (PIs), are very attractive materials that are capable of meeting the requirements of high-performance terminal devices that transmit broadband high-frequency signals. However, such a PI needs to be properly designed with appropriate properties, including a low Dk, low dielectric loss (Df), and low water absorptivity. PI materials are broadly used in various fields owing to their superior property/processibility combinations. This review summarizes the structural designs of PIs with low Dk and Df values, low water-absorbing capacity, and high optical transparency intended for communication applications. Furthermore, we characterize structure-property relationships for various PI types and finally propose structural modifications required to obtain useful values of the abovementioned parameters.

Effect of CuO doping on the performance of LaB6 interlayer films in Al/CuO:LaB6/p-Si/Al diodes

This study investigates the fabrication and performance analysis of Al/CuO:LaB6/p-Si/Al diodes with CuO-doped LaB6 interlayer films of varying concentrations (1%, 5%, and 10%). Experimental evidence demonstrates the limitations of 0% CuO doping, as pure LaB6 lacks a significant barrier height, resulting in ohmic behavior unsuitable for intended applications. Through comprehensive analyses under varying illuminations (20–100 mW/cm2) and frequencies (10 kHz–1 MHz), the study reveals that controlling CuO doping in LaB6 significantly enhances the effective barrier height at the LaB6:CuO heterojunction, improving rectification properties. This enhancement enables the diode to be well-suited for high-speed photonic devices utilizing one-step photoemission. The findings contribute to the development of high-performance LaB6-based devices, advancing photonic technologies by emphasizing the advantages of CuO doping.

Application of optical switching technology inalunar laser ranging system based on a superconducting detector.

The TianQin laser ranging station has successfully obtained the effective echo signals of the all five corner-cube reflectors on the lunar surface by using a 1064nm Nd:YAG laser with 100Hz repetition frequency and a 2×2 array of superconducting nanowire single-photon detectors (SNSPDs). The application of the SNSPD in the lunar laser ranging system (LLRS) has demonstrated its detection ability, but it loses its superconducting state and cannot work under strong stray light conditions. In this paper, a high-speed optical switch experimental device based on 100Hz is developed to solve the application problem of the SNSPD in the LLRS, and its main technical parameters are tested. The results show that the maximum running distance of the switch is 200µm; the switching time is better than 2ms; and the extinction ratio is better than 57dB. Moreover, the application of the high-speed optical switch experimental device in the lunar laser ranging system is designed, and the effective detection time between two laser pulses (10ms) is determined to be 6.1ms.

A High-Speed Device for Limiting Short-Circuit Currents Based on a Coil-Capacitor

A High-Speed Device for Limiting Short-Circuit Currents Based on a Coil-Capacitor

Design and Development of Ultrabroadband, High-Gain, and High-Isolation THz MIMO Antenna with a Complementary Split-Ring Resonator Metamaterial.

The need for high-speed communication has created a way to design THz antennas that operate at high frequencies, speeds, and data rates. In this manuscript, a THz MIMO antenna is designed using a metamaterial. The two-port antenna design proposed uses a complementary split-ring resonator patch. The design results are also compared with a simple patch antenna to show the improvement. The design shows a better isolation of 50 dB. A broadband width of 8.3 THz is achieved using this complementary split-ring resonator design. The percentage bandwidth is 90%, showing an ultrabroadband response. The highest gain of 10.34 dB is achieved with this design. Structural parametric optimization is applied to the complementary split-ring resonator MIMO antenna design. The designed antenna is also optimized by applying parametric optimization to different geometrical parameters. The optimized design has a 20 µm ground plane, 14 µm outer ring width, 6 µm inner ring width, and 1.6 µm substrate thickness. The proposed antenna with its broadband width, high gain, and high isolation could be applied in high-speed communication devices.

Aerodynamic Characteristics Analysis of Rectifier Drum of High-Speed Train Environmental Monitoring Devices

To study the aerodynamic characteristics of the convex structure of a surface-monitoring device on a high-speed train and to evaluate its impact on the aerodynamic performance of the high-speed train, numerical simulation research was conducted on three different layouts of the monitoring device. The computational fluid dynamics (CFD) method was used for the simulation study, and the unsteady compressible NS equation was used as the control equation. Hexagonal grid technology was used to reduce the demand for the grid quantity. The rationality of the grid size and layout was verified through grid independence research. To increase the accuracy of the numerical simulation, the γ-Reθ transition model and improved delayed detached eddy simulation (IDDES) method were coupled for the simulation research. The aerodynamic characteristics of the different operation directions and configurations were compared and analyzed. The research results showed that the windward side of the single pantograph detection device experienced positive pressure, and the sideline and leeward sides experienced negative pressure. Increasing the fillet radius of the sideline could appropriately reduce the aerodynamic resistance. When the speed was about 110 m/s, the drag force coefficient of the detection device was 210~410 N, and the lateral force was small, which means that it had little impact on the overall aerodynamic force of the train. According to the results of the unsteady analysis of the layout with a large space, the resistance during forward travel was greater than that during negative travel. The streamlined upwind surface was conducive to reducing the scope of the leeward separation zone and the amplitude of the pressure fluctuation in the leeward zone, and it thus reduced the resistance. For the running trains, a vortex was formed on their leeward surface. The pressure monitoring results showed that the separated airflow had no dominant frequency or energy peak. The possibility of the following train top and other components experiencing resonance damage is low.

Graphene-based field-effect transistor using gated highest-k ferroelectric thin film

We report a graphene-based highest-k ferroelectric field-effect transistor (GFE-FET) in which few-layer graphene sheets (FLGS) act as a channel layer and highest-k ferroelectric like barium zirconium titanate/barium calcium titanate (BZT/BCT) acts as an insulating gate layer. The electrochemical and sol-gel method has been used to prepare the used good quality FLGS and excellent BZT/BCT ferroelectric materials. SEM, XRD, UV–Vis, FTIR, and Raman spectroscopy measurements were done to characterize the produced materials. In order to evaluate the mobility of the fabricated GFE-FET, FET was fabricated with BZT/BCT gate and FLGS on top of it as conducting channel. The resultant field-effect mobility obtained from the fabricated GFE-FET is approximately ∼1.72 × 104 cm2V–1s−1 with 103 on/off ratio. These results ensure potential applications in some future high-speed electronic devices.

Magnetic field modulated ultrafast spin dynamics at Ni80Fe20/Neodymium interface.

Ultrafast spin dynamics is crucial for the next-generation spintronic devices towards high-speed data processing. Here, we investigate the ultrafast spin dynamics of Neodymium/Ni80Fe20 (Nd/Py) bilayers by the time-resolved magneto-optical Kerr effect. The effective modulation of spin dynamics at Nd/Py interfaces is realized by an external magnetic field. The effective magnetic damping of Py increases with increasing Nd thickness, and a large spin mixing conductance (∼19.35×1015 cm-2) at Nd/Py interface is obtained, representing the robust spin pumping effect by Nd/Py interface. The tuning effects are suppressed at a high magnetic field due to the reduced antiparallel magnetic moments at Nd/Py interface. Our results contribute to understanding ultrafast spin dynamics and spin transport behavior in high-speed spintronic devices.

High temperature stability of H-diamond high frequency MOSFET with 300°C grown Al2O3 dielectric

The high frequency H-diamond metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on single diamond substrate using 300°C ALD grown Al2O3 as gate dielectric and passivation layer. The devices gate length, gate/drain spacing and dielectric thickness are 100 nm, 2 μm, and 10 nm, respectively. The direct-current and frequency characteristics were investigated. The device shows a maximum saturation drain current of −492.6 mA/mm and gm of 135.2 mS/mm. The device shows good high temperature working performance, and the maximum saturation drain current only has a little decreasing of 7.6%. at 200°C. In addition, the device exhibits a maximum cut-off frequency of 36.2 GHz and maximum oscillation frequency of 70.5 GHz. The transient drain current response measurement indicates that the drain current can follow the changing of gate voltage at the frequency of 1 MHz. These results indicate that the Al2O3 dielectric is suitable for using in high frequency or the high-speed switching devices.

Glass fiber/polytetrafluoroethylene composite with low dielectric constant and thermal stability for high-frequency application

Dielectric composites with low dielectric constants (ε), low dielectric loss (tan δ), and excellent thermal-mechanical stability are highly desired for high signal transmission speed and high device integration. Polytetrafluoroethylene (PTFE) based composites exhibit tremendous potential due to the outstanding dielectric properties and high-frequency stability of PTFE. However, achieving PTFE-based dielectric composites with thermal-mechanical stability and low dielectric constant is challenging. Herein, we develop a glass fiber/polytetrafluoroethylene (GF/PTFE) composite for high-frequency communication applications with a designed skeleton structure. By the paper-making process, the glass fiber can be dispersed in random directions to set up a skeleton with the PTFE matrix entering the space in the fiber network. The modification of GF was also carried out to low down the dielectric loss of the composite. Benefiting from the supporting effect of the skeleton structure and surface modification, the thermal-mechanical stable dielectric composite was achieved with a low dielectric constant, and dielectric loss remained (m-GF content = 15 wt%, ε = 2.326 and tan δ = 5.24 × 10−3 at 30 GHz, xy-CTE = 29 ppm/°C and z-CTE = 47 ppm/°C). Moreover, the composites also have good dielectric constant frequency stability and thermal conductivity. Thus, this work provided an effective way to tailor the structure of functional composites with disordered fiber fillers.