Search Results (490)

Single-crystal diamond is regarded as one of the most promising semiconductor materials for next-generation high-power electronic devices, quantum technologies, and extreme environmental applications, owing to its ultra-wide bandgap, exceptionally high carrier mobility, ultra-high breakdown electric field, and excellent thermal conductivity. However, the lateral dimensions of both natural and synthetic single-crystal diamond are limited, which severely restricts their large-scale industrial application. Mosaic growth, in which multiple small single-crystal seeds are laterally arranged and fused at the interfaces through homoepitaxial growth, offers a promising approach to overcoming the size limitation of seed crystals and producing inch-scale single-crystal wafers. This review systematically covers the entire mosaic growth process, including seed crystal preparation, geometric design, growth parameter optimization, and innovative processing methods. Particular emphasis is placed on the mechanisms of interfacial stress generation, along with characterization techniques and stress control strategies. Finally, future perspectives on the fabrication of large-size, low-stress single-crystal diamond wafers are outlined. Full article

ZnS is one of the most promising wide-bandgap semiconductors for optoelectronic and sensing applications owing to its efficient ultraviolet–blue emission, high exciton binding energy, and chemical stability. However, the synthesis of ZnS nanocrystals in silicon-compatible porous matrices remains largely unexplored. In this work, ordered arrays of ZnS nanocrystals were synthesized for the first time in SiO₂/Si track templates fabricated by swift heavy ion irradiation followed by selective chemical etching. ZnS nanocrystals were deposited by electrochemical deposition from aqueous solutions containing ZnCl₂ and thiourea precursors. The structural, optical, and electrical properties of the resulting ZnS/SiO₂/Si nanocomposites were investigated using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, photoluminescence spectroscopy, and electrical measurements. The fabricated templates contained vertically aligned pores with a density of approximately 10⁸ cm⁻² and an average diameter of about 500 nm. Electrochemical deposition resulted in a pore filling efficiency of approximately 88%. X-ray diffraction analysis confirmed the formation of crystalline ZnS with a cubic zinc blende structure. The nanocomposites exhibit intense ultraviolet–blue photoluminescence in the 335–477 nm range, with pronounced emission peaks at 372 and 400 nm characteristic of ZnS nanocrystals. Current–voltage measurements indicate predominantly electronic conductivity, with a conductivity of 1.54 × 10⁻⁶ Ohm⁻¹·cm⁻¹, comparable to values reported for polycrystalline ZnS films. To support the experimental observations, the electronic structure of ZnS was analyzed using density functional theory within the LCAO framework. The calculated bandgap of 3.4 eV is consistent with previously reported theoretical and experimental data. The obtained results demonstrate that SiO₂/Si track templates provide a promising platform for the fabrication of ordered ZnS nanoarrays with potential applications in silicon-compatible optoelectronic and sensing devices. Full article

Rare-earth vanadates constitute an important class of functional materials with potential applications as luminophores, in optoelectronics and catalysis. The research for this work was inspired by the incomplete literature data, including the synthesis, structure and physicochemical properties of europium(III) vanadate(V) with the general formula Eu₅VO₁₀. The primary goal of this work was to supplement the missing data about this compound and identify its potential applications. This compound was synthesized using three methods, including waste-free methods: ceramic, mechanochemical and a modified Pechini method. The obtained Eu₅VO₁₀ was characterized using XRD, DTA–TG, FTIR, UV–Vis–DRS, SEM and gas pycnometry. It was settled that Eu₅VO₁₀ crystallizes in the monoclinic system and is thermally stable up to a temperature of approximately 1310 °C, above which it decomposes in the solid phase. Estimated energy gap (E_g) values ranged from ~3.21 eV to ~3.53 eV depending on the synthesis method used, allowing Eu₅VO₁₀ to be classified as a wide-bandgap electrical semiconductor. The results also showed that the synthesis method affects the crystallite size of the synthesized compound. The development of synthesis methods and characterization of Eu₅VO₁₀ expands our understanding of rare-earth vanadates and their potential applications as functional materials. Full article

We report a low-temperature plasma–liquid synthesis of crystalline β-Ga₂O₃ nanoparticles directly from aqueous solution. Pulsed discharge plasma bubbles generate reactive species that drive in situ dehydration and crystallization, bypassing the high-temperature calcination required by conventional methods. By varying the carrier gas, we tune morphology from uniform nanorice structures (He, Ar, and N₂) to amorphous microspheres (O₂ and air), revealing how plasma composition governs interfacial hydroxyl radical chemistry and growth kinetics. This approach demonstrates that localized plasma heating and reactive-species flux can achieve phase-selective oxide crystallization under ambient conditions, establishing plasma bubble reactors as a broadly applicable, low-temperature route for direct aqueous synthesis of crystalline wide-bandgap oxides that bridge solution chemistry and plasma nanomaterials design. Full article

Single-crystal diamond (SCD) is an ideal substrate material for semiconductor devices due to its extremely wide bandgap and exceptionally high thermal conductivity. However, diamond’s extreme hardness and chemical inertness pose challenges for the fabrication of ultra-smooth surfaces. Traditional polishing processes are not only inefficient but also prone to introducing subsurface defects, which severely degrade device performance. To address the above issues, this study proposes a hybrid polishing process combining reactive ion etching (RIE) surface modification with chemical mechanical polishing (CMP), which enables low-loss atomic-level processing of SCD. The study found that RIE treatment induces lattice disorder on the diamond surface, forming a sp²-hybridized amorphous carbon-modified layer. Compared to the sp³ structure of native diamond, this modified layer has lower hardness and is easier to remove. We conducted the verification of the optimized process using high-quality single-crystalline diamond (SCD) samples with an initial surface roughness Ra of 0.68 nm. Under the optimized RIE parameters (substrate bias power: 200 W, etching time: 600 s, gas flow ratio of Ar:O₂:CF₄ = 40:50:10), the surface roughness Ra was reduced to as low as 0.35 nm after 2 h of CMP treatment. Furthermore, systematic characterization of the SCD’s as-received surface, RIE-modified surface, and CMP-treated surface was performed using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), elucidating the “etching modification–mechanical removal” polishing mechanism. Full article

High-sensitivity detection of formaldehyde is critically important for environmental protection and public health. Zinc oxide (ZnO) is a widely used core material for chemiresistive gas sensors; however, its conventional low-index facets suffer from a limited number of active sites, creating a bottleneck for further sensitivity enhancement. To overcome this limitation, this study pioneers the application of the highly reactive ZnO $\left[20\overline{2}1\right]$ high-index polar surface for formaldehyde detection. By leveraging its unique stepped atomic configuration and unprecedented density of coordination-unsaturated active sites, we systematically investigate the formaldehyde adsorption behavior and the underlying sensing mechanism using first-principles calculations based on density functional theory (DFT). The pristine ZnO $\left[20\overline{2}1\right]$ surface exhibits intrinsic metallic character. At a coverage of 1 monolayer (ML), the most stable G1 configuration achieves an adsorption energy of −1.54 eV per CH₂O molecule. Within a 2 × 1 supercell, formaldehyde adopts both associative and dissociative adsorption modes. At a lower coverage, formaldehyde forms a stable bidentate structure through dual C–O and Zn–O bonding interactions. Electronic structure analysis reveals significant orbital hybridization and interfacial charge redistribution upon adsorption. Notably, associative adsorption opens a bandgap of 0.04 eV at the Fermi level, inducing a metal-to-semiconductor transition. In contrast, dissociative adsorption results in pronounced n-type doping, thereby elucidating the microscopic origin of the resistivity decrease observed in ZnO-based sensors. Overall, this work highlights the structural advantages of high-index facets and demonstrates for the first time the superior formaldehyde adsorption capability of the ZnO $\left[20\overline{2}1\right]$ facet, providing robust theoretical guidance for the rational design of next-generation, high-performance gas-sensing materials. Full article

Conventional photodetectors and image sensors deliver high-fidelity digital outputs but face a growing data-movement bottleneck: the energy and latency cost of transferring raw pixel streams to off-chip memory and processors increasingly dominates over both sensing and computation in modern machine-vision pipelines. An emerging response is the neuromorphic photodetector, a class of optoelectronic device that converts incident light into an electrical signal while simultaneously storing, modulating, and pre-processing that signal in a manner inspired by biological synapses and retinas. Over the past decade, demonstrations have spanned at least eight material platforms—organic semiconductors, organic–carbon-nanotube hybrids, perovskite and perovskite hybrids, metal oxides (including ultra-wide-bandgap and printable variants), wide-bandgap III-nitrides and 4H-SiC, two-dimensional materials, photo-memristors, and silicon CMOS in-sensor compute architectures—and have been realised through four distinct architectural families: phototransistor synapses, photo-memristors, heterojunction in-sensor compute, and linear photovoltaic neural networks. Here, we provide a quantitative cross-platform benchmark across forty in-scope articles, identify persistent photoconductivity as a near-universal device-physical substrate underlying synaptic functionality, characterise the responsivity–speed–energy trade-off structure observed across platforms, and present a critical assessment of energy-reporting practice in the field. We further identify three best-practice exemplars from three independent material platforms that converge on operating biases of 0.01–0.1 V and energies of 0.07–0.8 fJ per event, and we propose a unified reporting framework to enable meaningful cross-platform benchmarking of next-generation neuromorphic photodetectors. Full article

Thermal transient testing (TTT) is an essential technique for characterizing electronic systems, including packaged devices, modules, and subassemblies. These tests serve two closely related purposes: first, they enable determination of peak operating temperatures under various power conditions; on the other hand, they allow extraction of partial thermal resistances within the tested structure and identification of structural details near the active devices. The latter objective has become increasingly challenging with the advent of wide bandgap devices featuring extremely low on-state resistance, such as GaN HEMTs. This paper first identifies the temperature-sensitive electrical parameters and heater structures relevant for TTT of semiconductor devices. It then narrows the focus on GaN power devices and analyzes how external series resistances, originating from HEMT packages and the associated printed circuit boards, affect thermal impedances and structure functions. To remove the influence of these external resistances, which distort the extracted thermal descriptors, an analytical correction methodology has been developed. The proposed approach is validated through measurements performed on real devices. The results demonstrate that the method successfully restores the intrinsic thermal properties of the devices, yielding more accurate and physically meaningful thermal characteristics. Full article

The high-temperature operating requirements and the issues in the packaging process of wide-bandgap power semiconductors have positioned pressureless sinter-bonding using Ag nanoparticle paste as the most promising die-attach technology. However, under pressureless conditions, where externally applied pressure-driven particle rearrangement is absent, achieving sufficient densification and suppressing residual porosity during short-duration annealing at 250 °C remain significant challenges for conventional single-composition Ag pastes. In this study, a hybrid filler paste composed of Ag nanoparticles and a Ag complex solution was developed to implement an active mass supply strategy, in which additional Ag atoms were directly introduced into interparticle voids through in situ reduction during sinter-bonding. Mono-dispersed Ag nanoparticles with a mean diameter of 75.26 nm were synthesized via H₂O₂-mediated wet-chemical reduction, and the Ag complex solution was prepared using a Ag salt–complexing agent–formic acid system dispersed in an ethylene glycol medium. TG-DTA analysis of the hybrid paste revealed four sequential thermal stages, consisting of solvent evaporation, Ag ion reduction, organic decomposition, and interparticle sintering, accompanied by approximately 16 wt% out-gassing. Based on these results, a three-step temperature profile was designed to initiate sintering after complete out-gassing. When chip/paste/substrate assemblies, pre-dried at 50 °C for 90 s and pre-compressed at 5 MPa for 60 s, were subjected to the three-step profile with a peak temperature of 250 °C, the in situ reduced Ag effectively bridged adjacent nanoparticles and filled fine interparticle voids, leading to pronounced densification of the bond line. As a result, the hybrid paste achieved an average shear strength of 19.1 MPa, exceeding the minimum requirement for sinter-bonding applications. These findings demonstrate that the proposed hybrid filler approach provides an effective pathway for enhancing pressureless Ag sinter-bonding performance. Full article

Two-dimensional transition metal carbides and nitrides, known collectively as MXenes, are attractive photocatalyst candidates because their surface chemistry and atomic composition can be tuned over a wide compositional window. A crucial design quantity is the electronic bandgap, which selects whether a given MXene couples with solar radiation and aligns with the redox levels of water splitting. High-fidelity bandgap calculations using the PBE0 hybrid functional are computationally expensive, which has motivated several machine learning surrogates. To the best of our knowledge, this is the first study to integrate a continuous-depth Neural Ordinary Differential Equation backbone with multi-fidelity $\Delta$ learning, distribution-free split-conformal calibration, and uncertainty-aware Pareto screening into a single mathematically grounded pipeline for MXene bandgap prediction. In this work, we develop a physics-constrained neural ordinary differential equation (PC-NODE) that predicts MXene bandgaps from a compact 34-dimensional descriptor set, without relying on the density of states. The model couples a classifier head for the metal/semiconductor decision with a regression head for the gap magnitude, and enforces three physically motivated properties: non-negativity of the predicted gap and monotonicity between the low-fidelity Perdew–Burke–Ernzerhof (PBE) and the high-fidelity PBE0 estimates are obtained exactly through a softplus-parameterised $\Delta$ learning construction, while a hurdle coupling that drives metal predictions towards zero is enforced via a quadratic penalty and verified empirically. In short, two of the three physical constraints are guaranteed by construction, and the third is approximately enforced and verified empirically; the same distinction is maintained consistently in the methodology, the constraint audit and the conclusion. Trained on the 4356-structure MXgap database, a ten-seed ensemble reaches a mean absolute error of $0.186$ eV (per-seed $0.206\pm 0.006$ eV) and a coefficient of determination $R^2=0.880$ on the semiconductor test subset, with a classifier accuracy of $0.856$ and a Receiver Operating Characteristic Area Under the Curve (ROC-AUC) of $0.925$. A split-conformal calibration step then delivers prediction intervals whose empirical coverage matches the 90% target within 0.5 percentage points. Finally, an uncertainty-aware Pareto screening step applies the trained surrogate to a held-out subset of 396 lanthanum-based MXenes and identifies 74 candidates inside the photocatalytic water splitting window [1.23, 3.10] eV. The framework offers a mathematically grounded, data-efficient alternative to feature-heavy pipelines and is reproducible from the open MXgap resource. Full article

Gallium oxide is an ultra-wide bandgap semiconductor with excellent opto-electronic properties, making it a highly promising material for a wide range of applications and devices. In this article, we report how the optical, morphological, structural, and compositional properties of $\beta$-Ga₂O₃ thin films deposited by RF Sputtering on silicon substrates are affected by thermal treatments. Ellipsometric spectra recorded at multiple angles of incidence from several samples subjected to thermal annealing in the range of 550–1000 °C were analyzed to extract the optical functions using appropriate multilayer models. This analysis is complemented by compositional, structural, and morphological characterization techniques. We observed two main stages of crystallization with increasing annealing temperature; up to 700 °C, there is an increase in density and then, for 700–1000 °C, there is an improvement in crystallinity. While the refractive index increases continuously throughout this process, we found that the polarizability of the samples decreases in the first stage and increases in the second. These observations demonstrate that thermal treatments are a powerful tool to tune the optical properties of Ga₂O₃ thin films for device applications. Full article

Driven by demanding global emission regulations and the urgent requirements for sustainable mobility, Electric Vehicles (EVs) have emerged as the primary alternative to Internal Combustion Engine (ICE) vehicles. Central to this transition is the electric propulsion system (EPS), a multidisciplinary integration of power electronics, advanced motor drives, and electrochemical energy storage. This paper provides a comprehensive overview of the current landscape of power electronic drives, focusing on the evolution of high-efficiency traction motors and next-generation energy storage systems (ESSs), and advancements in ultra-fast chargers. The analysis explores the vital impact of power converters, evaluating recent breakthroughs in wide-bandgap (WBG) semiconductors and advanced control topologies that enhance energy density and thermal management. Furthermore, the study identifies critical challenges in the design, modulation, and operational reliability of converters under dynamic automotive environments. By synthesizing current research trends and technical bottlenecks, this paper offers insights into the future trajectory of power electronics in achieving high-performance, cost-effective, and carbon-neutral transportation. Full article

As a representative wide-bandgap semiconductor material, gallium nitride (GaN) has attracted increasing attention because of its superior material properties (e.g., high electron mobility, high electron saturation velocity, and critical electric field). For power electronics applications, and to take full advantage of the superiorities of the GaN material, the normally off operation is required based on an AlGaN/GaN heterostructure. For a commercial approach, GaN HEMTs with a p-GaN gate have become a research hotspot. The characteristics of p-GaN gate HEMTs have a significant relationship with gate structure, especially the contact type on the p-GaN layer. In this review, the necessity of normally off operation and the advantages of adopting a p-GaN gate are elaborated, followed by the theory of achieving normally off operation by p-GaN and critical fabrication processes. The various gate structures are discussed, including metal gate, junction gate and hybrid gate structures on the p-GaN layer, to improve threshold voltage. Meanwhile, the methods required to optimize breakdown voltage and monolithically integrated technologies are also demonstrated. This review outlines the development and future trends of p-GaN gate HEMTs for power systems. Full article

Off-grid electric vehicle (EV) charging infrastructure powered by hybrid solar–wind systems address critical adoption barriers in developing countries, where grid unreliability and sparse charging networks constrain transportation electrification. Despite growing research interest, no comprehensive review has systematically synthesized the interplay between hybrid renewable architectures, intelligent energy management strategies, and techno-economic viability specifically for off-grid EV charging in resource-constrained settings. This systematic review applies the PRISMA methodology to analyze 94 peer-reviewed publications (2013–2026), examining system architectures, intelligent control strategies, power electronics, battery storage, and deployment frameworks for standalone hybrid solar–wind EV charging stations. Key findings indicate that hybrid solar–wind configurations achieve 30–50% reductions in battery storage requirements and 15–25% lower levelized cost of energy (LCOE) (USD 0.08–0.15/kWh) compared with single-source systems, driven by diurnal and seasonal resource complementarity. Among intelligent control methods, the two-stage distributionally robust optimization (TSDRO) framework emerges as the most promising for data-scarce environments, outperforming conventional deterministic and stochastic approaches by 10–20% in managing renewable intermittency without requiring precise probability distributions. Wide-bandgap power semiconductors (SiC, GaN) enable 96–98% conversion efficiency, while lithium iron phosphate batteries provide 3000–5000 cycle lifetimes suited to tropical operating conditions. Critical gaps remain with field validation still predominantly simulation based, long-term operational data exceeding 24 months on equipment degradation and climate resilience are scarce, and scalable financing models for developing country contexts require further development. Nigeria is presented as an exemplar deployment context, with transferable insights for sub-Saharan Africa, South Asia, and Southeast Asia. Full article

Driven by global energy transformation and the progress of artificial intelligence technology, traditional automotive engineering is undergoing profound changes. Transportation is rapidly advancing toward electrification and intelligence. Against this background, this paper identifies three emerging paradigms for the development of electric vehicles: Heart Revolution, Brain Evolution, and Network Integration. This paper points out that automobiles are evolving from traditional one-way energy consumers to dynamic energy nodes in smart grids. With the support of artificial intelligence technology, the role of automobiles is also shifting from a simple means of transportation to an intelligent mobile terminal. At the same time, this paper focuses on analyzing the application of the integration theory of “Four Networks and Four Flows” in automobile upgrading. The theory does not focus on the optimization of a single node unit but emphasizes a systematic perspective to improve overall performance and support sustainable development. This paper suggests that the development of the automobile industry must be deeply integrated with the humanity world, information world and physical world. By building a five-in-one architecture of “Human–Vehicle–Road–Cloud–Satellite”, the automobile industry could follow a practical pathway toward coordinated development. At the same time, breakthroughs in core technologies such as solid-state batteries and wide-bandgap semiconductors are also imminent. This paper aims to provide a sustainable and high-performance automobile development path and integrate the concept of human-oriented design into it. Meanwhile, China’s new energy vehicle industry is used as a representative context to illustrate its engineering and industrial implementation. Full article