Defect Reduction Research Articles

Role of mechanical stress localizations on the radiation hardness of AlGaN/GaN high electron mobility transistors

Abstract Multi-material, multi-layered systems such as AlGaN/GaN high electron mobility transistor (HEMTs) contain residual mechanical stresses that arise from sharp contrasts in device geometry and materials parameters. These stresses, which can be either tensile or compressive, are difficult to detect and eliminate because of their highly localized nature. We propose that their high stored internal energy make potential sites for defect nucleation sites under radiation, particularly if their locations coincide with the electrically sensitive regions of a transistor. In this study, we validate this hypothesis with molecular dynamic simulation and experiments exposing both pristine and annealed HEMTS to 2.8 MeV Au+3 irradiation. Our unique annealing process uses mechanical momentum of electrons, also known as the electron wind force (EWF) to mitigate the residual stress at room temperature. High-resolution transmission electron microscopy (TEM) and cathodoluminescence spectra reveal the reduction of point defects and dislocations near the two-dimensional electron gas region of EWF-treated devices compared to pristine devices. The EWF-treated HEMTs showed relatively higher resilience with approximately 10% less degradation of drain saturation current and ON-resistance and 5% less degradation of peak transconductance. Both mobility and carrier concentration of the EWF-treated devices were less impacted compared to the pristine devices. Our results suggest that the lower density of nanoscale stress localization contributed to the improved radiation tolerance of the EWF-treated devices. Intriguingly, the EWF is found to modulate the defect distribution by moving the defects to electrically less sensitive regions in the form of dislocation networks, which act as sinks for the radiation induced defects and this assisted faster dynamic annealing.

Unraveling the influence of defects in Janus MoSSe and Janus alloys MoS2(1−x)Se2x

We investigate the effect of structural and substitutional defects in Janus MoSSe and the Janus alloys MoS2(1−x)Se2x by a comprehensive analysis. Distinct Raman signatures are associated with various defect types and densities, mirroring the evolution from MoSe2 to Janus alloys to ideal Janus MoSSe. By the corresponding stoichiometrical and structural changes, the band gap can be tuned from 1.50 eV up to 1.68 eV at room temperature. Electrical characterization in a field effect device uncovers the impact of defects on conductivity, mobility (up to 2.42 × 10−3 cm2 V−1 s−1), and threshold voltages. A decrease of n-type doping of 5.3 × 1011 cm−2 in Janus MoSSe compared to the Janus alloy points towards an increased work function and a reduction of defects. Our findings deepen the understanding of defect physics in 2D Janus materials and pave the way for tailored defect engineering strategies for advanced (opto-)electronic applications.

Equilibrium densities of intrinsic defects in transition metal diselenides of molybdenum and tungsten.

Point defects are thermodynamically stabilized in all crystalline materials, with increased densities negatively impacting the properties and performance of transition metal dichalcogenides (TMDs). While recent point defect reduction methods have led to considerable improvements in the optoelectronic properties of TMDs, there is a clear need for theoretical work to establish the lower limit of defect densities, as represented by thermal equilibrium. To that end, an abinitio and thermodynamic analysis of the equilibrium densities of intrinsic point defects in MoSe2 and WSe2 is presented. The intrinsic defect formation energies at the limits of the selenium and metal-rich regimes are determined by density functional theory (DFT) and then augmented with elemental chemical potential functions to determine temperature- and pressure-dependent formation energies. Equilibrium defect densities are determined for MSe, SeM, vM, and vSe, where M and v, respectively, represent the metal and the vacancy, as a function of synthesis temperature and pressure. The effects of vibrational free energy contributions and treatment of the DFT exchange-correlation potential are found to be non-negligible. Calculated equilibrium densities are several orders of magnitude below reported defect densities in TMDs made by chemical vapor deposition, chemical vapor transport, and flux methods, thereby establishing that current synthesis methods are either kinetically limited or impurity dominated.

Digital Engineering in Photonics: Optimizing Laser Processing

This article explores the transformative impact of digital engineering on photonic technologies, emphasizing advancements in laser processing through digital models, artificial intelligence (AI), and freeform optics. It presents a comprehensive review of how these technologies enhance efficiency, precision, and control in manufacturing processes. Digital models are pivotal for predicting and optimizing thermal effects in laser processing, thereby reducing material deformation and defects. The integration of AI further refines these models, improving productivity and quality in applications such as micromachining and cladding. Additionally, the combination of AI with freeform optics advances laser technology by enabling real-time adjustments and customizable beam profiles, which enhance processing versatility and reduce material damage. The use of digital twins is also examined as a key development in laser-based manufacturing, offering significant improvements in process optimization, defect reduction, and system efficiency. By incorporating real-time monitoring, machine learning, and physics-based modeling, digital twins facilitate precise simulations and predictions, leading to more effective and reliable manufacturing practices. Overall, the integration of digital twins, AI, and freeform optics into laser processing marks a significant progression in manufacturing technology. These advancements collectively enhance precision, efficiency, and adaptability, resulting in improved product quality and reduced operational costs. The continued evolution of these technologies is expected to drive further advancements in manufacturing practices, offering more robust solutions for complex production environments.

Lower leg shortening technique in treatment of the wounded with gunshot tibial fractures

Background. The severity of gunshot wounds to the extremities is due to the formation of bone and soft tissue defects. The relevance of this publication is determined by the need to introduce simple and effective methods into the practice of providing assistance to the wounded. The technique under consideration fully satisfies these requirements. The aims of the study: 1) to optimize the lower leg shortening technique and analyze the short-term results of its application in treatment of the wounded with gunshot tibial fractures; 2) to assess the indications for surgical restoration of the lower leg length after its shortening. Methods. The study enrolled 45 wounded patients with gunshot fractures of the lower leg bones. Reconstructive interventions were performed on 51 segments. In the absence of purulent-necrotic lesions of the fragments ends, closed reduction and convergence to tight contact without resection were performed (13 cases, group I). In the case of necrosis of the fragments ends, resection and convergence were performed with significant shortening of the segment (38 cases, group II). Results. The amount of shortening accounted for 4 cm [3; 6] in group I and 8 cm [7; 10] in group II (p0.001). Due to the convergence of the fragments, the reduction of the soft tissue defect was 25 cm2 [11; 41] and 38 cm2 [20; 81] in group I and II respectively. In 2 (15.4%) patients in group I and 4 (10.5%) patients in group II no fusion occurred. In the remaining cases the fusion occurred, the consolidation period was 50 [45; 59] weeks in group I and 36.5 [29; 43] weeks in group II (p0.001). Conclusions. Depending on the condition of fragments ends, there are two possible options of the shortening technique: without resection and with resection of the fragments ends. Shortening without resection is possible in the absence of signs of fragment necrosis. The disadvantage is the risk of delayed fusion, the advantage is the ability to avoid traumatic intervention in the form of resection of the fragments ends. In case of the fragments ends necrosis, their transverse resection and convergence with the elimination of diastasis between them is necessary. The advantage of this shortening technique is the optimization of conditions and reduction of fusion time, the disadvantage is the formation of significant bone defects. The need for lengthening of the shortened segment does not always arise. Lengthening as a second stage after conducting rehabilitation is considered as an optimal choice.

Development and Application of Digital Twin Control in Flexible Manufacturing Systems

Flexible manufacturing systems (FMS) are highly adaptable production systems capable of producing a wide range of products in varying quantities. While this flexibility caters to evolving market demands, it also introduces complex scheduling and control challenges, making it difficult to optimize productivity, quality, and energy efficiency. This paper explores the application of digital twin technology to tackle these challenges and enhance FMS optimization and control. A digital twin, constructed by integrating simulation models, data acquisition, and machine learning algorithms, was employed to replicate the behavior of a real-world FMS. This digital twin enabled real-time dynamic optimization and adaptive control of manufacturing operations, facilitating informed decision making and proactive adjustments to optimize resource utilization and process efficiency. Computational experiments were conducted to evaluate the digital twin implementation on an FMS equipped with robotic material handling, CNC machines, and automated inspection. Results demonstrated that the digital twin significantly improved FMS performance. Productivity was enhanced by 14.53% compared to conventional methods, energy consumption was reduced by 13.9%, and quality was increased by 15.8% through intelligent machine coordination. The dynamic optimization and closed-loop control capabilities of the digital twin significantly improved overall equipment effectiveness. This research highlights the transformative potential of digital twins in smart manufacturing systems, paving the way for enhanced productivity, energy efficiency, and defect reduction. The digital twin paradigm offers valuable capabilities in modeling, prediction, optimization, and control, laying the foundation for next-generation FMS.

CD44 facilitates adhesive interactions in airineme-mediated intercellular signaling.

Specialized cellular protrusions facilitate local intercellular communications in various species, including mammals. Among these, airinemes play a crucial role in pigment pattern formation in zebrafish by mediating long-distance Notch signaling between pigment cells. Remarkably, airinemes exhibit large vesicle-like structure at their tips, which are pulled by macrophages and delivered to target cells. The interaction between macrophages and Delta-ligand carrying airineme vesicles is essential for initiating airineme-mediated signaling, yet the molecular detail of this interaction remains elusive. Through high-resolution live imaging, genetic in vivo manipulations and in vitro adhesion assay, we found that adhesive interactions via the extracellular domain of CD44, a class I transmembrane glycoprotein, between macrophages and airineme vesicles are critical for airineme signaling. Mutants lacking the extracellular domain of CD44 lose their adhesiveness, resulting in a significant reduction in airineme extension and pigment pattern defects. Our findings provide valuable insights into the role of adhesive interactions between signal-sending cells and macrophages in a long-range intercellular signaling.

Enhanced Stability Under Positive Bias Temperature Stress in Oxide Thin Film Transistors with Double Gate Structure By Improving Bottom Channel Interface

In this paper, we discuss the causes of reliability degradation in oxide TFTs with a double gate structure and propose methods for improvement. Reducing IGZO deposition power significantly improves PBTS (Positive Bias Temperature Stability) reliability in double gate structures. This improvement is attributed to reduction of excess oxygen defects accumulated at the bottom channel interface, as inferred from the difference in PBTS results for the top single gate and double gate structures

Microservices architecture to enable an open platform for realizing zero defects in cyber-physical manufacturing

Abstract The market’s demand for high-quality products necessitates innovative manufacturing approaches that emphasize flexibility, adaptability, and the reduction of defects. Traditional systems are currently evolving towards embracing I4.0 technologies, including data collection, processing, analytics and digital twin, aiming for zero-defect manufacturing quality. This paper introduces an open platform, compliant with RAMI4.0 standards, designed to improve manufacturing quality. The platform integrates data using Asset Administration Shells with microservices adaptation for data ingestion and advanced analytics. Additionally, it incorporates Non-Destructive Inspection tools, demonstrating a seamless integration of measurement and quality assurance. This study details the architectural specification and validation of the openZDM platform, employing microservices to ensure flexibility, modularity and scalability, aligning with the RAMI4.0 model. The platform was validated through deployment in an automotive assembly line, highlighting its effectiveness in integrating inspection scenarios and early defect detection tools. The architecture employs a choreographed approach to manage loosely coupled microservices, enabling efficient data lifecycle management from collection through analytics to visualization.

The Advanced Analysis of Deep Drawing Processes for 1-Inch Diameter Dop-Pipe Caps: Simulation and Experimental Insights

This article investigates the challenges and solutions within the deep drawing process, focusing on issues like cracks and deviations from standard thickness dimensions. Utilizing both experimental methods with a 40-ton power press machine and numerical simulations via ABAQUS software, the study uses SPCC-SD steel to produce a Dop-pipe 1-inch diameter pipe cap. Key findings reveal significant correlations in elements E-90 and E-91, with minimal disparities of around 4.5% between experimental and numerical approaches, showcasing the accuracy of numerical predictions. Notably, the numerical simulations identify potential issues such as increased thickness due to higher axial forces, providing valuable insights for process optimization and defect reduction. By advancing the deep drawing process and extending its applicability to broader material-forming applications, this research contributes significantly to enhancing production efficiency and improving manufacturing practices, emphasizing the importance of simulation-driven approaches in achieving precision and quality enhancement in complex manufacturing processes.

Influence of process parameters on the organization and properties of 316L-SCBCC bracket formed by selective zone laser melting

Abstract 316L porous skeletal scaffolds prepared by selective laser melting (SLM) technology are currently widely used in bone injuries. Its successful implantation is predicated on having properties that match those of natural bone. The process parameters significantly influence the performance of SLM-316L porous scaffold. In this study, the nine-group shaping process parameters were determined by orthogonal method. The 316L porous scaffolds were tested in compression, electrochemistry, XRD and microstructure. The influence of process parameters on the performance of body-centered cubic peripheral square structure bracket was investigated. The influence laws of process parameters on microstructure, mechanical properties and corrosion resistance were obtained. The results show that process parameters have a significant effect on the microstructure, properties and defect distribution. The reduction of defects and grain refinement in the stent is conducive to the improvement of compressive properties and hardness of the stent. The magnitude of the hardness is inversely related to the grain size. The corrosion current density of porous scaffolds are also affected by their microscopic defects and grain size. At an energy density of 78.70 J mm−3 presents the least defects and obtains smaller grains, resulting in the best mechanical properties and corrosion resistance.

GPI anchoring controls cell wall integrity, immune evasion and surface localization of ChFEM1 for infection of Cochlibolus heterostrophus1

Glycosylphosphatidylinositol (GPI) anchoring is one of the common post-translational modifications in eukaryotic cells. In fungi, it exerts a wide range of biological functions by targeting proteins to the cell wall, but only few studies focus on the roles of GPI anchoring in plant pathogenic fungi. Here, we reveal a role of GPI anchoring in the maize fungal pathogen Cochlibolus heterostrophus. We found that GPI-anchored proteins were widely accumulated in hyphae, appressorium and infection hyphae of C. heterostrophus. Deletion of ChGPI7, which encodes a key enzyme involved in the biosynthesis of GPI anchors, resulted in significant reduction of vegetative growth and conidiation, as well as virulence due to impairment of appressorium formation and invasive growth. The ΔChgpi7 mutants also showed severe defects in cell wall integrity, resulting in a significant reduction of stress resistance. Deletion of ChGPI7 and hydrofluoric acid (HF) pyridine treatment both led to removal of cell wall GPI-anchored proteins and exposure of chitin, the results suggested that GPI anchored proteins could protect chitin from host immune recognition. A total of 124 proteins were predicted to be GPI anchored proteins in C. heterostrophus, including a putative cell wall glycoprotein ChFEM1. Deletion of ChFEM1 also resulted in significant reduction in virulence and defects in infection structures, as well as cell wall integrity. We further found that cell wall localization and protein abundance of ChFEM1 were affected by ChGPI7. Our results showed that GPI anchoring regulates cell wall integrity and immune evasion for infection of C. heterostrophus.

Optimizing the uncertainty of measurements on a coordinate measuring machine when controlling complex geometric surfaces

The object of this study is the process of optimizing measurement uncertainty on a coordinate measuring machine (CMM) when inspecting complex geometric surfaces. The problem addressed was insufficient accuracy and efficiency of measurements of complex parts on CMMs under production conditions. A method for optimizing measurement uncertainty has been devised, which includes a mathematical model of the measurement process and an adaptive algorithm for optimizing the control strategy, based on the Monte Carlo method. The model takes into account the geometry of surfaces and CMM characteristics, while the algorithm dynamically adjusts measurement parameters. The results demonstrate a reduction in measurement uncertainty by 15–20 % and a reduction in inspection time by 10–12 % compared to conventional methods. This is achieved by taking into account the specificity of complex surface geometry and an adaptive approach. The uniqueness of the developed method is the ability to automatically adapt to different types of CMMs and measured objects, optimizing the number and location of measurement points, the speed of probe movement, and its contact force with the surface. The method takes into account not only the geometric parameters of objects but also the characteristics of the CMM itself, which allows for high accuracy. The method is particularly effective for parts with complex geometry, in which conventional methods often lead to significant errors. Practical application is possible at machine-building enterprises for quality control of complex parts, especially in serial production. The implementation of the developed method allows for improving product quality and reducing production costs by 8–10 % due to optimization of the control process and reduction of defects

Enhanced Photocatalytic Performance under Ultraviolet and Visible Light Illumination of ZnO Thin Films Prepared by Modified Sol-Gel Method.

Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5-15.7 nm were prepared by applying a novel two-step drying procedure involving hot air treatment at 90-95 °C followed by conventional furnace drying at 140 °C. For comparison, layers were made by standard furnace drying. The effect of hot air treatment on the film surface morphology, transparency, and photocatalytic behavior during the degradation of Malachite Green azo dye in water under ultraviolet or visible light illumination is explored. The films treated with hot air demonstrate significantly better photocatalytic activity under ultraviolet irradiation than the furnace-dried films, which is comparable with the activity of unmodified ZnO nanocrystal powders. The achieved percentage of degradation is 78-82% under ultraviolet illumination and 85-90% under visible light illumination. Multiple usages of the hot air-treated films (up to six photocatalytic cycles) are demonstrated, indicating improved photo-corrosion resistance. The observed high photocatalytic activity and good photo-corrosion stability are related to the hot air treatment, which causes a reduction of oxygen vacancies and other defects and the formation of interstitial oxygen and/or zinc vacancies in the films.

SiC MOSFET Gate Oxide Quality Improvement Method in Furnace Thermal Oxidation with Lower Pressure Control

We have investigated carbon behavior resulting from pressure control in furnace thermal oxidation process and evaluated the effect on gate oxide quality resulting from this pressure control. In order to investigate the potential reduction of carbon defects by reducing CO and CO2, an analysis of oxidized SiC wafers was conducted. To evaluate the effect of pressure control related carbon component change during thermal oxidation, QBD characteristic was evaluated in SiC MOS Capacitance. The analysis results revealed on observable decrease in carbon at the SiO2/SiC interface and the SiO2 layer. The QBD results shown that improved at lower pressure better than those obtained in the general pressure.

Crystal Originated Defect Monitoring and Reduction in Production Grade SmartSiC™ Engineered Substrates

Power devices electronics based on Silicon Carbide (SiC) are emerging as a breakthrough technology for various applications. The link between the quality of SiC substrates and device performance has been widely discussed [1]. Smart Cut™ technology offers the opportunity to integrate a high quality SiC layer on a low resistivity handle wafer. Moreover the crystal quality of a single donor wafer can be replicated multiple times to provide an epitaxy-ready substrate in high volume [2]. Nevertheless, some extended grown-in defects of SiC starting material, like micro-pipes or bulk inclusions, may generate surface defects called "Crystal Originated Defects" (COD) on transferred layers. This paper explains how SmartSiC™ defect density can be reduced by limiting the number of extended defects on donor wafers. Specific inspection recipes were developed to monitor the starting material and the replicated engineered substrate: COD root-causes and effects were analyzed. We demonstrated how a well-suited quality control of donor wafers plays a major role to guarantee defect-free SmartSiC™ wafers.

A Study of Process Interruptions during Pre- and Post-Buffer Layer Epitaxial Growth for Defect Reduction in 4H SiC

We perform epilayer growth where the process is interrupted (in situ) during post and pre buffer layer growth at a reduced temperature. Process interrupted during post buffer layer growth demonstrates significant reduction in basal plane dislocation (BPD) at a lower temperature. SIMS study demonstrates that etching takes place during the interruption time. We believe surface treatment of the buffer layer at different etching conditions during the interruption plays a major role in BPD reduction. However, the in-situ interruption, taking place prior to the buffer layer (i.e., on the substrate), does not contribute to the reduction in BPD in epilayer. We believe that the surface effect of interruption related etching on substrate during pre-buffer layer interruption, is not efficient enough to reduce BPD due to the higher doping and higher BPD associated with the substrate. Furthermore, we demonstrate that post buffer layer growth interruption contributes to the reduction in stacking faults in the epilayers. We also attribute this reduction of SF due to the surface etching prior to the drift layer growth.

Introducing Bi2S3 Interlayer to Synergistically Modify Mo Back Contact and Regulate Bulk Defects in Kesterite Solar Cells.

A suitable interlayer between the Mo back electrode and kesterite absorber layer has been proven to have a positive effect on limiting the bulk defects of the absorber by the constitute diffusion. Here, a thin Bi2S3 layer is used as the back-interface intermediate layer for the first time, this innovative approach allows for simultaneous modification of the back contact and reduction of bulk defects, resulting in improving the power conversion efficiency of the kesterite device from 9.66% to 11.8%. The evaporated Bi2O3 thin films turn into the Bi2S3 interlayers after sintering the Cu2ZnSnS4 precursor thin films. The Bi2S3 interlayer can inhibit the decomposition reaction of back contact and suppress the formation of the secondary phases. It can also optimize the Fermi level offset and promote the separation of the photoinduced carriers, resulting from its characteristic of high work function. Besides, a small part of the Bi element can diffuse into Cu2ZnSn(S, Se)4 film and induce the crystal growth and restrain Zn-related defects, which is attributed to forming the low melting-point liquid BiSex phase during the high-temperature selenization process. The conclusions highlight the bifunction of the thin Bi2S3 intermediate layer, which can provide a new approach to improve the photoelectric conversion efficiency of kesterite solar cells.

Fabrication of transparent glass fabric‐reinforced thermoplastic composite based on tow‐spreading technique

AbstractHighly transparent and mechanically robust thermoplastic composites have been developed by hot‐pressing PETG with E‐glass fabrics. The tow‐spreading technique facilitates the reduction of internal defects and fiber crimp angle in the composites, thereby significantly improving their optical and mechanical properties. The optimized composite containing 55.1 vol% glass fibers and 0.4 mm thickness has a high transmittance of 86.1%@616 nm and a low overall haze of 7.2%. Moreover, the 1 mm thick composites exhibit tensile strength of up to 340 MPa and impact strength of up to 86.3 kJ/m2. After 28 days of hygrothermal or UV aging, the composites show minimal changes in their glass transition temperature and thermal degradation temperature. The chemical structure also remains unchanged, with no observed crystallization. In comparison to UV aging, the composites demonstrate better resistance against hygrothermal aging. Specifically, the hygrothermal aged sample displayed a light transmittance retention rate of 93.5% and a bending strength retention rate of 94.3%, while these values were reduced to 73.3% and 90.5%, respectively, in the UV aged sample. The opto‐mechanical properties enhanced mechanism and aging degradation mechanism have been identified by microscopic morphological observation. This work provides an innovative and straightforward approach to fabricate transparent, recyclable, high‐strength thermoplastic composites.Highlights Highly transparent, mechanically robust, recyclable glass‐fabric reinforced thermoplastic composites are fabricated. Composites with spread‐tow fabrics exhibits improved transparency. The fabrication route is scalable and cost‐effective. The mechanism for opto‐mechanical properties enhancement are proposed.

Outcome of posterior lamellar replacement with oral mucous membrane graft in lid margin sequalae of Steven Johnson syndrome

: to address common lid margin sequalae presented in steven Johnson syndrome and to assess the outcome of posterior lamellar replacement with oral mucous membrane graft. : This single center longitudinal study was conducted in Ispahani Islamia Eye Institute and Hospital. 56 diagnosed cases of Steven Johnson syndrome with lid margin sequalae during the period of July 2020 to June 2023 were included in the study. Patients with ocular cicatrizing pemphigoid and chemical burn were excluded from the study. Demographic profile, presenting lid margin sequalae, outcome of surgery and complication after intervention and its management were properly evaluated and recorded. : A total of 98 eyelids (upper and lower) in 56 patients were evaluated. The Mean age was 38.33 ± 15.22 years (range 6 – 70 years). 21 patients were male and 35 were female (male: female=1:1.66). 14 patients had unilateral defect and 42 patients have bilateral defect. Most common lid margin sequalae was lid margin keratinization (85.71%), distichiasis (62.5%), trichiasis (21.42%) and entropion (8.92%). All lid margin defect were successfully corrected by posterior lamellar replacement with oral mucous membrane graft. During 6 months post-operative follow up, significant symptomatic relief from epiphora, foreign body sensation, pain and photophobia were achieved in all patients. There was remarkable reduction of conjunctival inflammation (88.63%) and persistent corneal epithelial defect (71.42%). Mean visual acuity was significantly improved. Common complications of the surgery were misdirected lashes (7.14%), dislodgement of graft (2.04%%), and recurrent entropion (2.04%). All complication was successfully managed through appropriate second procedure.Posterior lamellar resection with an oral mucous membrane graft for modifying lid margin defects in Steven-Johnson syndrome shows promising results.