Device Processing Research Articles

Harnessing a WOx-based flexible transparent memristor synapse with a hafnium oxide layer for neuromorphic computing.

Transparent memristor-based neuromorphic synapses are expected to be specialised devices for high-speed information transmission and processing. The synaptic linearity and potentiation/depression cycles are imperative issues for the application of memristors. This work explores a memristor for improving switching uniformity by introducing a thin HfOx interfacial layer as a diffusion-limiting layer sandwiched between WOx and ITO bottom electrodes. An optimized HfOx thickness not only provides the best switching properties but also shows superior synaptic properties. The optimized 15 nm thin WOx layer can retain the memristor's excellence in P/D linearity, a cycling stability of 494 epochs and image recognition up to 3 mm bending, making it suitable for flexible devices. The artificial synapse is capable of reversible short-term and long-term learning behaviors confirmed by spike-timing-dependent-plasticity (STDP) results. X-ray photoelectron spectroscopy confirms the device composition and provides the oxygen vacancy concentration at the WOx/HfOx interface to realize the switching mechanism. The thicknesses of the different layers are estimated from the high-resolution transmission electron microscopy observations. The fabricated device exhibits 92.2% transparency, as confirmed by the UV-Vis spectrum.

Ferroelectricity-controlled magnetic ordering and spin photocurrent in NiCl2/GeS multiferroic heterostructures

Controlling magnetism solely through electrical means is indeed a significant challenge, yet holds great potential for advancing information technology. Herein, our investigation presents a promising avenue for electrically manipulating magnetic ordering within 2D van der Waals NiCl2/GeS heterostructures. These heterostructures, characterized by their unique magnetic-ferroelectric (FE) layer stacking, demonstrate spin-constrained photoelectric memory, enabling low-power electrical writing and non-destructive optical reading. The two orientations of the polarization in the GeS FE layer bring about changes in the ground state configuration, transitioning from ferromagnetic (FM) to antiferromagnetic (AFM) orderings within the NiCl2magnetic layer. Correspondingly, the light-induced charge transfer prompts either spin-polarized or unpolarized currents from the FM or AFM states, serving as distinct '1' or '0' states, and facilitating applications in logic processing and memory devices. This transition stems from the interplay of interfacial charge transfer mechanisms and the influence of the effective electric field (Eeff), bringing a non-volatile electric enhancement in the magnetic anisotropy energy within the NiCl2/GeS heterostructure. Overall, our study highlights the NiCl2/GeS heterostructure as an optimal candidate for realizing spin-dependent photoelectric memory, offering unprecedented opportunities for seamlessly integrating memory processing capabilities into a single device through the utilization of layered multiferroic heterostructures.

Cloud-edge collaborative high-frequency acquisition data processing for distribution network resilience improvement

To realize transparent monitoring and resilience improvement of low-voltage distribution network, both the data acquisition scope and frequency have been greatly expanded. Cloud-edge collaboration leverages the edge server’s real-time response capabilities and the cloud server’s robust data processing power to enhance the performance of high-frequency data acquisition processing. Nonetheless, it continues to confront challenges such as the entanglement of optimization variables, the presence of uncertain information, and a lack of awareness regarding acquisition frequencies. In this paper, we propose a machine learning-based cloud-edge collaborative data processing optimization algorithm to minimize the weighted sum of data processing delay and device energy consumption for distribution network resilience improvement. The joint optimization problem is decoupled into device-edge data offloading subproblem and edge-cloud data splitting subproblem, which are solved by the proposed upper confidence bound (UCB) based frequency-aware device-edge data offloading optimization algorithm and the exponential-weight algorithm for exploration and exploitation (EXP3) based edge-cloud data splitting optimization algorithm, respectively. Simulation results show that the proposed algorithm is superior to existing algorithms in performances of energy consumption and total processing delay.

Atomic-Thin WS2 Kirigami for Bidirectional Polarization Detection.

The assembly and patterning engineering in two-dimensional (2D) materials hold importance for chip-level designs incorporating multifunctional detectors. At present, the patterning and stacking methods of 2D materials inevitably introduce impurity instability and functional limitations. Here, the space-confined chemical vapor deposition method is employed to achieve state-of-the-art kirigami structures of self-assembled WS2, featuring various layer combinations and stacking configurations. With this technique as a foundation, the WS2 nano-kirigami is integrated with metasurface design, achieving a photodetector with bidirectional polarization-sensitive detection capability in the infrared spectrum. Nano-kirigami can eliminate some of the uncontrollable factors in the processing of 2D material devices, providing a freely designed platform for chip-level multifunctional detection across multiple modules.

Digital Cellulose: Recent Advances in Electroactive Paper

With the increasing global demand for net-zero carbon emissions, actions to address climate change have gained momentum among policymakers and the public. The urgent need for a sustainable economy is underscored by the mounting waste crisis in landfills and oceans. However, the proliferation of distributed electronic devices poses a significant challenge due to the resulting electronic waste. To combat this issue, the development of sustainable and environmentally friendly materials for these devices is imperative. Cellulose, an abundant and CO2-neutral substance with a long history of diverse applications, holds great potential. By integrating electrically interactive components with cellulosic materials, innovative biobased composites have been created, enabling the fabrication of bulk electroactive paper and the establishment of new, potentially more sustainable manufacturing processes for electronic devices. This review explores recent advances in bulk electroactive paper, including the fundamental interactions between its constituents, manufacturing techniques, and large-scale applications in the field of electronics. Furthermore, it addresses the importance and challenges of scaling up production of electroactive paper, highlighting the need for further research and development.

Identification of digital device hardware vulnerabilities based on scanning systems and semi-natural modeling

Objectives. The development of computer technology and information systems requires the consideration of issues of their security, various methods for detecting hardware vulnerabilities of digital device components, as well as protection against unauthorized access. An important aspect of this problem is to study existing methods for the possibility and ability to identify hardware errors or search for errors on the corresponding models. The aim of this work is to develop approaches, tools and technology for detecting vulnerabilities in hardware at an early design stage, and to create a methodology for their detection and risk assessment, leading to recommendations for ensuring security at all stages of the computer systems development process.Methods. Methods of semi-natural modeling, comparison and identification of hardware vulnerabilities, and stress testing to identify vulnerabilities were used.Results. Methods are proposed for detecting and protecting against hardware vulnerabilities: a critical aspect in ensuring the security of computer systems. In order to detect vulnerabilities in hardware, methods of port scanning, analysis of communication protocols and device diagnostics are used. The possible locations of hardware vulnerabilities and their variations are identified. The attributes of hardware vulnerabilities and risks are also described. In order to detect vulnerabilities in hardware at an early design stage, a special semi-natural simulation stand was developed. A scanning algorithm using the Remote Bitbang protocol is proposed to enable data to be transferred between OpenOCD and a device connected to the debug port. Based on scanning control, a verification method was developed to compare a behavioral model with a standard. Recommendations for ensuring security at all stages of the computer systems development process are provided.Conclusions. This paper proposes new technical solutions for detecting vulnerabilities in hardware, based on methods such as FPGA system scanning, semi-natural modeling, virtual model verification, communication protocol analysis and device diagnostics. The use of the algorithms and methods thus developed will allow developers to take the necessary measures to eliminate hardware vulnerabilities and prevent possible harmful effects at all stages of the design process of computer devices and information systems.

Supercapacitor properties of partially oxidised-MXene quantum dots/graphene hybrids: Fabrication of flexible/wearable micro-supercapacitor devices

Recently, combining the synergistic properties of two-dimensional (2D) and zero-dimensional (0D) materials has attracted significant attention for energy applications. Here, we report the synthesis and characterization of partially oxidised-MXene quantum dots (PO-MXQDs) and reduced graphene oxide composite (PO-MXQDs/rGO) and investigate the resulting composites for energy storage applications towards supercapacitors. Density functional theory (DFT) simulations are used to examine the electrical and structural features of PO-MXQDs/rGO by predicting the chemical interaction involving charge transfer from PO-MXQDs to rGO. The multilayer Artificial Neural Network (ANN) model with hyperparameter tuning was developed at different input parameters to optimize material compositions, concentrations, and types of electrolytes to obtain the suitable conditions for best supercapacitive performance. The optimized PO-MXQDs/rGO showed a specific capacitance value of 1137.8 F.g−1 and was utilized for the fabrication of flexible micro-supercapacitors (FMSCs) device through the mask-assisted vacuum filtration process and asymmetric coin-cell type supercapacitor devices (ACCDs). The FMSCs deliver a higher areal capacitance (5.26 mF.cm−2), high areal energy density (0.46 μWh.cm−2), high areal power density (210.48 μW.cm−2), and the FMSC device has ultra-high cyclic stability up to 30000 cyclic voltammetry (CV) cycles. This method provides an in-depth study on developing 0D-2D hybrid materials with the wisdom of machine learning (ML) and DFT toward energy storage applications.

Simulation calculation of the cooling process of phase change cold storage devices in rail vehicles under natural convection conditions

Simulation calculation of the cooling process of phase change cold storage devices in rail vehicles under natural convection conditions

Laser Direct Writing for Micromachining of Freeform Surface on n-Type GaAs via Photoelectrochemical Etching

The fabrication of microstructures featuring freeform surfaces on semiconductor substrates confronts substantial obstacles due to their inherent material difficulties, including considerable hardness and brittleness, as well as geometric complexity. In this investigation, we leverage laser direct writing (LDW) combined with photoelectrochemical etching to achieve precise material removal from semiconductor surfaces. By conducting a series of experiments on a home-made LDW apparatus under varying conditions, we established a correlation between the etching depth and both the power intensity and motion speed of the laser spot. The analysis revealed that the etching depth exhibited linearly with the power intensity of the laser spot and inversely with the motion speed. Additionally, the half widths of the grooves maintained consistently within the range of 1–2 μm. By leveraging this methodology, we successfully fabricated a freeform micro-optical structure on an n-GaAs wafer by precisely adjusting the power intensity of the laser spot during scanning, thus demonstrating the feasibility for achieving nanoscale machining precision. This research underscores the promise of this technique in significantly advancing the fabrication processes of semiconductor devices.

Printed circuit board and printed circuit board assembly methods for testing and visual inspection: a review

Testing and visual inspection of printed circuit boards (PCBs) and printed circuit board assemblies (PCBAs) are important procedures in the manufacturing process of electronic modules and devices related to locating and identifying possible defects and failures. Earlier defects detection leads to decreasing expenses, time and used resources to produce high quality electronics. In this paper an exploration and analysis about the current research regarding methods for PCB and PCBA testing, techniques for defects detection and vusial inspection is performed. The impact of machine and deep learning for testing and visual inspection procedures is also investigated. The used methodology comprises bibliometric approach and content analysis of papers, indexed in scientific database Scopus, considering the queries: “PCB and testing” and “PCB and testing”, “printed circuit board assembly and testing” and “PCBA and testing”, “PCB defect detection” and “PCBA defect detection”, “PCB and visual inspection”, and “PCBA and visual inspection”. The findings are presented in the form of a framework, which summarizes the contemporary landscape of methods for PCBs and PCBAs testing and visual inspection.

Numerical simulation research on the launch process of pneumatic launch device

Abstract In order to deal with the potential threats posed by low-altitude UAVs, an anti-UAV net-catching device was designed based on the principle of pneumatic launch. The internal ballistic calculation model of the net-catching device during the launch process was established, and the pressure-stabilizing air chamber of the device was numerically simulated. The impact of pressure, air chamber volume, gas channel diameter and barrel length on the performance of the launch device to capture the UAV was analyzed. The internal relationship between different influencing factors on the muzzle velocity and the air pressure drop of a single shot was analyzed. Selecting appropriate internal ballistic characteristics to capture UAVs at different target distances provides theoretical guidance for in-depth research on anti-UAV netting devices.

Comparison of computer-assisted sperm analysis and smartphone-applied sperm analysis for evaluation of frozen-thawed bull semen.

This study aims to compare the efficacy of computer-assisted sperm analysis (CASA) and smartphone-applied sperm analysis (SASA) in assessing the quality of frozen-thawed bull semen. A total of 75 straws (n = 75) semen samples were used from different production batches of five Holstein bulls. The semen analyses were conducted in three groups: Group I (CASA-37°C), semen samples were evaluated using the CASA system at 37°C (n = 25); Group II (SASA-25°C), semen samples were assessed using the SASA system at a temperature of room heat (25°C) (n = 25); and Group III (SASA-37°C), semen samples were evaluated using the SASA system at 37°C (n = 25). The frozen-thawed bull semen samples were analysed in terms of total motility (TM), progressive motility (PM), immotile, velocity average path (VAP), velocity curve linear (VCL), velocity straight line (VSL) and sperm concentration. There was no significant difference between the groups in terms of spermatozoa concentration (p > .05). However, significant differences among the groups were observed for total motile spermatozoa values (p < .001). Values of progressive motile spermatozoa were lower in Group I and Group II compared to Group III (p < .001). The immotile spermatozoa values were significant between the groups (p < .001) and were found to be proportional to total motile spermatozoa values. Additionally, the VAP, VCL and VSL values were comparable between Group II and Group III, but lower when compared to Group I. In conclusion, the results of the study demonstrate that the Sperm Cell™ system can accurately analyse the concentration of frozen-thawed bull semen. The analyses performed at room temperature indicate a parallelism between the PM value and CASA results. However, it is thought that SASA devices require a series of standardization studies in different semen extenders, different sample concentrations and different animal species, analogous to the standardization evolution process of CASA devices in semen analysis.

Design of image classification system for fabric inspection process using Raspberry Pi

This research is designed as a prototype of defect inspection system on fabric production using machine learning-based image processing technology using the open source Google teachable machine application integrated with Raspberry Pi-3B. The prototype of fabric defect inspection system is built by utilizing two rollers that function as a fabric roll house before and after the inspection process. On both rollers, a fabric is stretched to be inspected, so that from a roll of fabric with a certain length, it can be seen how many defects occur on the fabric. The inspection system is carried out using a web camera with a certain level of lighting connected to a raspberry pi as a control device. Raspberry Pi functions as an image processing device and fabric rolling motor controller. In addition to the category of fabric in good condition, this system classifies into two categories of defects, namely slap defects and sparse defects. The test results show that this system has an average frame per second (FPS) of 4.85, an average inference time of 181.1 ms, with an accuracy of image classification results of 98.4 %.

Silk fibroin as a surfactant for water-based nanofabrication.

Water-based processing plays a crucial role in high technology, especially in electronics, material sciences and life sciences, with important implications in the development of high-quality reliable devices, fabrication efficiency, safety and sustainability. At the micro- and nanoscale, water is uniquely enabling as a bridge between biological and technological systems. However, new approaches are needed to overcome fundamental challenges that arise from the high surface tension of water, which hinders wetting and, thus, fabrication at the bio-nano interface. Here we report the use of silk fibroin as a surfactant to enable water-based processing of nanoscale devices. Even in minute quantities (for example, 0.01 w/v%), silk fibroin considerably enhances surface coverage and outperforms commercial surfactants in precisely controlling interfacial energy between water-based solutions and hydrophobic surfaces. This effect is ascribed to the amphiphilic nature of the silk molecule and its adaptive adsorption onto substrates with diverse surface energy, facilitating intermolecular interactions between unlikely pairs of materials. The approach's versatility is highlighted by manufacturing water-processed nanodevices, ranging from transistors to photovoltaic cells. Its performance is found to be equivalent to analogous vacuum-processed devices, underscoring the utility and versatility of this approach for water-based nanofabrication.

Design and field experiment of Codonopsis pilosula film covering transplanter

To address the low efficiency and high labor demands of manual Codonopsis pilosula cultivation, as well as the limitations of existing flat-type transplanting machines that create trenches of inconsistent depth hindering root growth and seedling emergence, a C. pilosula film-covered outcrop tilted transplanting machine was developed. Based on theoretical analysis of the prototype's key components and agronomic requirements for oblique C. pilosula transplanting, the structure and working parameters of the rotary tiller soil throwing device, soil lifting device, track-type soil conveying device, seedling throwing device, and film covering device were determined. The core components' working principles were analyzed, and the soil throwing process of the rotary tiller device was simulated using the discrete element method (DEM). A calculation domain was established, and the results showed that the average mass of the rotary tiller device was 49.44 kg, while the required soil lifting amount for the scraper-type soil lifting device was 21.84 kg, meeting the soil throwing requirements. Field experiments in 10 test areas demonstrated an average qualified rate of 89.50% for planting depth, 84.00% for planting posture, 90% for exposed plant spacing, 4.51 cm for plant spacing, and 8.67% coefficient of variation for planting spacing. These results meet industry standards for planting depth and planting spacing, confirming the machine's effectiveness in achieving high-quality tilted transplanting of C. pilosula seedlings.

Enhanced fluorescence properties of polyfluorene–based polymer dots through an ascorbic acid-photoaging treatment for living cell imaging

The polymer dots (Pdots) prepared by the conjugated polymer (PFO, poly (9,9-dihexylfluorene-2,7-diyl)) have high fluorescence intensity and are often used in biological fluorescence imaging. However, due to the chain defects, the PFO Pdots suffer from stability issues such as photoinactivation and photobleaching. To solve this problem, we drew inspiration from the preparation process of organic planar light-emitting devices and added an optimization processing after Pdots was prepared. We used illumination as the driving force to activate defects on its chain, and ascorbic acid as a reducing substance to restore the chain defects of the polymer to a more stable state. Through this method, we increased the fluorescence intensity by nearly 1.9 times, and significantly improving their long and short-term stability. In addition, it ensures other properties remain unchanged. This optimization scheme is also fully compatible with the entire biological imaging process, ensuring that other important properties such as cytotoxicity do not undergo unnecessary changes. Furthermore, we conducted material characterization and theoretical simulation, revealing that the optimization scheme mainly serves to repair C-9 alkyl defects on the polyfluorene unit. This study has improved and enhanced the fluorescence performance of PFO Pdots, and also provides a way to optimize the treatment of other similar conjugated polymer material systems.

Broadband vortex beam generation by a reflective meta-surface based on a metal double-slit resonant ring

Recently, the meta-surface (MS) has emerged as a promising alternative method for generating vortex waves. At the same time, MS also faces the problem of a narrow bandwidth; in order to obtain a broad bandwidth, the MS unit cell structure becomes more and more complex, which will bring many inconveniences to the preparation process of MS devices. Therefore, we want to design a simple MS unit cell with a multi-frequency selection. In this paper, based on the principle of geometric phase, we design a simple reflective MS unit cell based on a metal double-slit resonant ring. We elaborate on the resonance mechanism of the MS unit cell. Under the normal incidence of circularly polarized (CP) waves, the reflection coefficient of the same polarization was greater than 85%. By rotating the orientation angle of the resonator on the MS unit cell, the continuous 2π phase coverage was satisfied in the frequency range of 0.52–1.1 THz, and the relative bandwidth becomes 71.6%. Based on this, we construct a vortex generator by using a 15×15 MS unit array. The right-handed circularly polarized (RCP) waves and left-handed circularly polarized (LCP) wave are separately incident on MS with topological charges of l=+1,+2,+3 under multiple resonant frequencies. The generated RCP vortex wave has topological charges of l=−1,−2,−3 and the generated LCP vortex wave has topological charges of l=+1,+2,+3. The numerical simulation results demonstrate that our designed MS, capable of achieving multiple resonance outcomes, can effectively operate in a multi-broadband mode and produce a wide-band vortex beam. In addition, we also calculate the pattern purity. Through theoretical analysis and numerical simulation, we prove that our designed MS can generate a broadband vortex wave.

Control of spin on structural stability, mechanical, magneto-optoelectronic and thermodynamic properties of RbTaX (X =P and As) materials: Emerging candidates for opto-spintronics and spin filter applications

In the present work, the density functional theory has been utilised in inspecting the ground state-structural, electronic, magnetic, optical, elastic and thermodynamic properties of new semiconductor RbTaX (X = P and As) half-Heuslers. Out of the possible three structures (α, β, γ) studied in ferromagnetic (FM) as well as non-magnetic (NM) phases, α – FM phase is found to be the most stable configuration. Both studied materials have estimated a net magnetic moment of 3μB, following the Slater-Pauling rule (Mtot=Ztot−8). With the use of modified Becke Johnson potential (mBJ) potential, the band profile reveals non-zero band gap in the spins and henceforth display spin filter property in the compounds. The predicted energy band gaps for RbTaP and RbTaAs are 3.04 and 2.87 eV for minority spin channels and 0.137 and 0.26 eV for majority spin channels, respectively. This unique feature of the Heusler compound may be advantageous for quantum information processing and spin-transport in electronic and magnetic devices. Also, a moderate exchange splitting and a Curie temperature well above the room temperature are noted. The stability of the materials under investigation was further confirmed by calculations of cohesive energy, formation energy, and second order elastic constants. The optoelectronic as well as thermodynamic properties of the studied compounds are also investigated. The estimated high value of refractive index (>4) is making them suitable for optical lenses. Moreover, photon energy absorption in the visible and ultraviolet spectrums renders them valuable for UV-VIS absorbers.

Rapid Detection of Cleanliness on Direct Bonded Copper Substrate by Using UV Hyperspectral Imaging.

In the manufacturing process of electrical devices, ensuring the cleanliness of technical surfaces, such as direct bonded copper substrates, is crucial. An in-line monitoring system for quality checking must provide sufficiently resolved lateral data in a short time. UV hyperspectral imaging is a promising in-line method for rapid, contactless, and large-scale detection of contamination; thus, UV hyperspectral imaging (225-400 nm) was utilized to characterize the cleanliness of direct bonded copper in a non-destructive way. In total, 11 levels of cleanliness were prepared, and a total of 44 samples were measured to develop multivariate models for characterizing and predicting the cleanliness levels. The setup included a pushbroom imager, a deuterium lamp, and a conveyor belt for laterally resolved measurements of copper surfaces. A principal component analysis (PCA) model effectively differentiated among the sample types based on the first two principal components with approximately 100.0% explained variance. A partial least squares regression (PLS-R) model to determine the optimal sonication time showed reliable performance, with R2cv = 0.928 and RMSECV = 0.849. This model was able to predict the cleanliness of each pixel in a testing sample set, exemplifying a step in the manufacturing process of direct bonded copper substrates. Combined with multivariate data modeling, the in-line UV prototype system demonstrates a significant potential for further advancement towards its application in real-world, large-scale processes.

PDMS micro check valve with 3D valve disk for reducing fluid resistance

Check valves are essential components in various biomedical, chemical, medical diagnostic, and process applications, as they allow fluid flow in the forward direction while blocking the reverse flow. This paper presents a method to enhance the performance of unibody micro check valves composed of polydimethylsiloxane using 3D design and printing technologies. Passive micro check valves, which are known for their structural simplicity, miniaturization, and light weight, have shown improved performance with the application of 3D valve disks formed via 3D printing technology. The performance of various valve disk designs was evaluated using simulations and experiments, which revealed that cone-shaped 3D valve disks offer a 58.33% improvement in blocking pressure performance compared to traditional two-dimensional designs. This underscores the potential for efficient fluid control in micro check valves using 3D structures while highlighting the importance of 3D printing technology in the design and manufacturing processes of microfluidic devices.