Search Results (451)

Ultrawide bandgap (UWBG) semiconductors are destined to become the foundation for next-generation power and radio-frequency (RF) electronic devices. Their superior qualities such as high thermal conductivity, strong critical electric field, and robust mechanical and radiation hardness are driving continuous and widespread research. Amongst the UWBG materials, aluminum nitride (AlN) is highly attractive due to its direct ultrawide bandgap of about 6.2 eV, resulting in one of the highest Baliga’s and Johnson’s figures of merit. Equally important as its properties are material availability and growth methods capable of producing large-diameter substrates. In this work we report on bulk growth of 100 mm AlN crystals using the physical vapor transport (PVT) technique. The thermal gradients were simulated and tailored to obtain adequate thermal stresses, resulting in substrates with narrow X-ray rocking curves and dislocation densities in the range of 10²–10⁵ cm⁻². In addition, the room-temperature thermal conductivity measured in two directions, perpendicular and parallel to the c-axis, was confirmed to be 300 W m⁻¹ K⁻¹. AlN substrates also demonstrated high UV transparency with absorption coefficients as low as 10 cm⁻¹ at 265 nm wavelength. These results, along with the availability of 100 mm substrates, demonstrate that AlN is ready for further exploration and development for the power and RF electronics industry. Full article

Optical spectroscopy provides useful information about polymeric ultrathin films by combining interferometric and optical absorption data contained in the UV-Vis-NIR spectra. In particular, the UV-Vis-NIR spectrum of an ultrathin polymeric film contains information about the film thickness, structural disorder, bandgap energy, type of electron transition model (direct/indirect, allowed/forbidden), cutoff wavelength (i.e., the opaque/transparent switching wavelength), etc. Here, these properties have been determined for a model semi-crystalline polymer (polyethylene terephthalate, PET) in the form of ultrathin film before and after a mild mechanical deformation treatment (manual stretching). It has been found that E_U and E_g parameters are not strictly dependent on mechanical deformation due to their main dependence on the chemical composition/constitution of the polymer. Full article

Soft magnetic materials determine the efficiency, size, thermal burden, and reliability of transformers, inductors, electrical machines, electromagnetic interference (EMI) components, and magnetic sensors. This review differs from property-by-property surveys by using a condition-aware, application-driven framework: magnetic performance is compared only together with frequency, peak magnetic flux density, temperature, waveform, direct current (DC) bias, geometry, and processing route. After a concise treatment of coercivity, permeability, saturation polarization, magnetostriction, and loss mechanisms, the major material families are quantitatively compared in terms of magnetic performance, processing, cost, and industrial maturity. The review then maps these families onto grid transformers, high-speed electrical machines, wide-bandgap power converters, integrated magnetics, wireless power transfer, aerospace electrical systems, and radiofrequency components. Particular attention is given to the trade-offs among saturation polarization, permeability, core loss, mechanical strength, thermal stability, manufacturability, and sustainability. Recent advances in strong and ductile soft magnets, wide-temperature ferrites, vortex and easy-plane composites, mixed-powder soft magnetic composites, nanocrystalline flake-ribbon cores, and additive manufacturing are assessed by technology maturity. A prioritized roadmap identifies near-term needs for standardized condition-specific data and manufacturing control, medium-term opportunities in magnetic–thermal co-design and digital twins, and longer-term prospects for adaptive, self-healing, and GHz magnetic architectures. The resulting framework is intended to support both material development and defensible industrial material selection. Full article

This article presents a review and comparative analysis of converter architectures for electrolyzer systems, covering alternating current (AC) -grid-connected, direct-current (DC) -grid-connected, and renewable-energy-connected systems, as well as isolated and non-isolated configurations. The study classifies and compares key converter topologies based on engineering criteria, including voltage gain, efficiency, device count, control complexity, and implementation feasibility. Furthermore, the relationships among converter structures, power-source characteristics, and electrolyzer-system requirements are analyzed to reveal system-level engineering trade-offs. The analysis demonstrates that converter suitability depends on the combined requirements of the power source, galvanic isolation, electrolyzer characteristics, operating conditions, and application-specific engineering priorities. In addition, wide-bandgap semiconductor devices and electrolyzer operating characteristics are discussed as important factors in converter selection, particularly for improving converter efficiency, reducing current ripple, increasing power density, and supporting dynamic operation. This article therefore provides a systematic framework for converter classification and selection according to power-source characteristics, electrolyzer requirements, and application power levels. Full article

Ultraviolet (UV) radiation is a major environmental factor contributing to photoaging, oxidative stress, inflammation, DNA damage, and photocarcinogenesis. Conventional UV filters, although widely used in sunscreen formulations, are associated with limitations including photoinstability, photocatalytic ROS generation, potential toxicity, and environmental concerns. In recent years, plant-mediated nanomaterials have emerged as promising multifunctional photoprotective systems, combining UV attenuation with antioxidant, anti-inflammatory, and biologically adaptive properties. Plant extracts are increasingly used as reducing and stabilising agents in the green synthesis of metal and metal oxide nanoparticles. Among these, ZnO and TiO₂ serve as established inorganic UV filters, whereas Ag and Au nanoparticles have primarily been investigated for their antioxidant, anti-inflammatory, antimicrobial, and ROS-modulating properties, which may indirectly enhance photoprotection. In parallel, plant-derived organic nanoparticles and herbal nanocomposites have demonstrated enhanced biocompatibility and multifunctional performance. This review critically examines the current landscape of plant-mediated photoprotective nanomaterials, focusing on the mechanistic interplay among optical UV attenuation, reactive oxygen species (ROS) modulation, and cellular signalling regulation. Particular emphasis is placed on structure–function relationships governing nanoparticle size, surface chemistry, bandgap properties, antioxidant behaviour, and biological interactions. The review further discusses translational challenges, including reproducibility, standardisation, scalability, long-term safety, regulatory classification, and limitations in benchmarking. Importantly, current evidence suggests that no single material system simultaneously optimises UV-blocking efficiency, ROS control, biocompatibility, and industrial scalability, highlighting the need for multifunctional hybrid design strategies. Finally, future perspectives involving predictive nanoengineering, computational modelling, machine learning-guided optimisation, and adaptive photoprotective systems are discussed as emerging directions for next-generation sustainable photoprotective technologies. Full article

Zinc oxide (ZnO) is a wide-bandgap semiconductor with important optoelectronic, photonic, and radiation-related applications. In this work, hydrothermally grown ZnO bulk single crystals were irradiated with fast neutrons and characterized using low-temperature photoluminescence (PL) spectroscopy to investigate irradiation-induced changes in the Ga-related donor-bound exciton (I₈). The Zn-polar surfaces were exposed to fast neutrons for irradiation durations of 2 and 5 min. The PL measurements showed a reproducible enhancement of the Ga-related I₈ emission intensity, with increases of approximately 33% after 2 min and 82% after 5 min relative to the unirradiated reference crystal. The selective enhancement of the I₈ emission is consistent with increased Ga-related donor activity associated with the proposed Zn-to-Ga neutron transmutation mechanism, although irradiation-induced defect formation and redistribution may also contribute to the observed optical response. Under the irradiation conditions investigated, fast-neutron exposure produced substantial enhancement of the I₈ emission within only a few minutes. However, direct quantitative comparison with previously reported slow-neutron irradiation should be interpreted with caution because the two studies employed different neutron energies, fluences, and irradiation conditions. These findings demonstrate the potential of fast-neutron irradiation for modifying the low-temperature optical response of hydrothermally grown ZnO and provide a foundation for future investigations of neutron-induced defect and donor engineering in wide-bandgap oxide semiconductors. Full article

Autonomous robotic systems designed for extraterrestrial in situ resource utilization (ISRU) will play a central role in enabling a sustained human presence on the Moon and Mars. These robots are expected to perform tasks such as regolith excavation, water extraction, oxygen production, and propellant generation under extremely harsh environmental conditions, including large temperature variations, abrasive dust, high radiation levels, and significant communication delays with Earth. Consequently, their onboard electrical systems must operate with high reliability, autonomy, and fault tolerance. A critical enabling technology for these systems is the isolated power conversion architecture, which distributes energy from primary power sources to multiple robotic subsystems, including mobility actuators, drilling systems, sensors, computing units, and thermal management modules. Future lunar and Martian missions are expected to rely on a combination of alternative energy sources, including solar photovoltaic arrays with energy storage, fuel cells, radioisotope power systems, and nuclear surface power reactors, which can provide continuous and high-density energy independent of sunlight availability. These diverse power sources require flexible and highly efficient isolated DC–DC power conversion architectures capable of managing wide input voltage ranges while ensuring electrical isolation, safety, and system stability across distributed robotic platforms. This literature review surveys recent developments in autonomous isolated power conversion architectures suitable for lunar and Martian resource extraction robots. The review examines advanced converter topologies such as resonant converters, phase-shifted full-bridge converters, dual-active bridge converters, and modular multiport power converters designed for high efficiency, high power density, and scalable power distribution. Emphasis is placed on converter architectures capable of interfacing with nuclear-powered systems and other high-energy-density sources while supporting distributed loads in robotic mining and processing systems. In addition, the paper reviews emerging autonomous control strategies, including adaptive digital control, intelligent power management, fault detection and self-recovery mechanisms, and distributed power architectures capable of maintaining stable operation under dynamic load conditions. The role of wide-bandgap semiconductor technologies, including silicon carbide (SiC) and gallium nitride (GaN), is also examined, highlighting their potential to enable higher switching frequencies, improved efficiency, reduced system mass, and enhanced thermal performance in vacuum environments. Finally, system-level considerations for integrating isolated power conversion within robotic ISRU platforms are discussed, including redundancy strategies, power bus architectures, electromagnetic compatibility, thermal management, and long-duration reliability requirements. By consolidating advances across power electronics, autonomous control, and space power systems, this review identifies key research gaps and outlines design directions for next-generation autonomous power conversion systems capable of supporting scalable lunar and Martian resource extraction infrastructures powered by both renewable and nuclear energy sources. Full article

Nanostructured copper oxide (CuO) holds significant promise for optoelectronic, photocatalytic, and biomedical applications, yet its performance is critically dictated by its morphology, crystallite size, and surface chemistry. In this work, pure monoclinic CuO nanoparticles were successfully synthesized via a facile, kinetically controlled aqueous co-precipitation route using three distinct precursor salts: copper acetate (CO-Ac), copper sulfate (CO-S), and copper chloride (CO-Cl). To achieve precise architectural control, the synthesis was conducted near the thermodynamic solubility limit of the precursors combined with an abrupt NaOH injection, effectively decoupling the nucleation stage from crystal growth. Rietveld refinement of X-ray diffraction (XRD) data confirmed the structural integrity of the monoclinic lattice across all samples, χ² = 1.04 − 2.02, crystallinity 53–55%, while demonstrating that the precursor anion strongly governs the volume-averaged crystallite size, which expanded from 16 nm (CO-Ac) to 30 nm (CO-S) and 52 nm (CO-Cl). Morphological analyses revealed that acetate acts as a non-specific capping ligand, promoting isotropic, quasi-spherical nanoparticles that aggregate into high-surface-area (69.04 m²/g) “bead-chain” assemblies. Conversely, sulfate and chloride ions act as shape-directing agents via facet-selective adsorption on nucleation seeds, yielding two-dimensional plates and anisotropic acicular/needle-like architectures, respectively. X-ray photoelectron spectroscopy (XPS) and modified Auger parameter (α ~1851 eV) analyses confirmed the absolute dominance of Cu²⁺ states, with a minor fraction (~2.5 mol %) of lower-coordinated surface edge states. XPS further unveiled that the strongly alkaline environment (pH ~14) drives precursor-dependent surface chemistry: CO-Ac nanoparticles retain a clean, hydroxylated layer with minor acetate residues, whereas CO-S and CO-Cl samples develop a passive copper hydroxycarbonate (Cu₂(OH)₂CO₃) surface barrier that blocks active sites and reduces porosity. Optical properties analyzed via UV-vis diffuse reflectance revealed a pronounced, size-dependent blueshift relative to bulk CuO, with fundamental indirectly allowed bandgaps of 2.6 eV, 2.36 eV and 1.93 eV for CO-Ac, CO-S and CO-Cl samples, while the direct bandgaps shifted from 3.0 eV, 3.2 eV, and 3.57 eV for the mentioned samples. This behavior is attributed to quantum confinement governed by fine individual nanocrystals. These findings establish that precursor engineering offers a robust pathway to tailor the morphological, optical, and interfacial properties of CuO nanostructures for targeted functional devices. Full article

The condensation reaction of pyromellitic dianhydride and (aminomethyl)phosphonic acid in imidazole yielded N,N′-bis(phosphonomethyl)pyromellitimide ([(H₂O₃P)CH₂-(C₁₀H₂N₂O₄)-CH₂(PO₃H₂)]∙2H₂O). Recrystallization of this compound from deionized water, by placing the solution in a desiccator to allow slow diffusion of HCl, afforded suitable single crystals for X-ray crystallographic studies. The compound crystallizes in the monoclinic space group P2₁/n. The flexible methylene phosphonic acid groups appended to both nitrogen termini adopt a trans configuration. The phosphonate and carbonyl groups (acceptors: P=O and C=O), together with water molecules [donor: O(6)—H∙∙∙O], participate in an extensive network of hydrogen-bonding interactions. Two of the phosphonate groups are protonated as P—OH (donors) and interact with oxygen atoms of neighboring phosphonate groups and water molecules. Hirshfeld surface analysis and associated two-dimensional fingerprint plots indicate that O∙∙∙H/H∙∙∙O (56.1%) contacts are the primary contributors to the crystal packing, followed by H∙∙∙H (16.3%) and C∙∙∙O/O∙∙∙C (13.4%) interactions. No significant π–π interactions were observed. The direct optical bandgap value, estimated from the Tauc plot, is 3.24 eV, indicating semiconducting behavior. The compound also exhibits thermal stability up to ~270 °C. These properties suggest that this compound may be a promising candidate for future investigation in organic electronic and optoelectronic materials. Full article

Wide-bandgap (WBG) power converters impose stringent requirements, including high-frequency switching, strongly nonlinear dynamics, and limited computational time, which constrain conventional control and artificial intelligence (AI)-based approaches and hinder their practical deployment. Existing review studies have primarily focused on algorithmic structures or performance, while systematic analyses from a deployment feasibility perspective under hardware constraints remain limited. This paper examines AI applications in WBG power converters from a system-level deployment perspective and analyzes existing studies based on implementation feasibility. After outlining the physical characteristics and control requirements of WBG devices, it reviews AI-based modeling, AI-assisted model predictive control (MPC), and reinforcement learning (RL)-based direct control. These approaches are evaluated in terms of computational complexity, real-time feasibility, out-of-distribution (OOD) generalization, and integration with conventional control frameworks. Key deployment challenges, including safety-constrained RL, sim-to-real transfer, and field-programmable gate array (FPGA)/embedded implementation, are treated as core analytical dimensions. To support this assessment, this review introduces an AI Deployment Readiness framework organized around four analytical dimensions: (1) modeling accuracy, (2) safety assurance, (3) sim-to-real transfer capability, and (4) hardware implementability. Using this framework, prior studies are reassessed, and its applicability is further discussed for applications such as fault diagnosis and remaining useful life (RUL) prediction. The analysis identifies key bottlenecks and clarifies deployment-relevant considerations for high-frequency WBG systems. Full article

Perovskite solar cells (PSCs) have reached certified efficiencies exceeding 26%, yet the gap to the Shockley–Queisser limit and insufficient operational stability remain key obstacles to commercialization. Quantum dots (QDs) offer a versatile platform to address both challenges through their size-tunable bandgaps, high photoluminescence yields, and solution processability. This review systematically examines four QD integration strategies in PSCs: transport layer modification, active layer doping, UV conversion layers, and tandem sub-cells. The underlying mechanisms—including defect passivation, energy-level engineering, crystallization control, and ion migration suppression—are critically compared across these approaches. Despite significant advances, challenges persist, including the ligand–charge transport trade-off, the environmental toxicity of Pb/Cd-containing QDs, poor reproducibility, and the absence of standardized stability testing protocols. By providing a mechanism-oriented assessment across all device components, this review offers a clear framework for selecting appropriate QD strategies and identifies priority research directions. The perspective of QD strategies in this review provides a useful and significant reference for approaching the theoretical PCE limits of single-junction PSCs by reducing non-radiative recombination and improving light utilization, while QD-based tandem architectures offer a viable route toward surpassing the single-junction Shockley–Queisser limit. Full article

Copper selenide (Cu₂Se), as a typical p-type narrow bandgap semiconductor, has garnered significant attention in the fields of thermoelectrics and optoelectronics due to its inherent low thermal conductivity, high Seebeck coefficient, low cost, and environmental friendliness. Compared with bulk materials, Cu₂Se thin films exhibit unique advantages in microdevice integration and flexible applications, holding great potential for applications in flexible thermoelectric generators, solar cells, and photodetectors. This article systematically reviews the research progress of Cu₂Se thin films, focusing on key preparation parameters such as growth temperature, annealing conditions, copper/selenium element ratio, and substrate type, and elucidates their regulation of film microstructure, crystal phase structure, and thermoelectric/optoelectronic properties. It delves into the mechanisms of doping strategies such as carrier concentration regulation, band engineering, and defect modification, clarifying the synergistic optimization effects of different doping elements on conductivity, Seebeck coefficient, and thermal conductivity. The article summarizes the current application status of Cu₂Se thin films, points out existing challenges such as poor process reproducibility and insufficient thermal stability, and anticipates future research directions such as multi-parameter synergistic optimization and heterojunction design, providing a systematic reference for the development and practical application of high-performance Cu₂Se-based functional thin films. Full article

Two-dimensional (2D) semiconductors have attracted significant attention for their potential in low-power and high-performance electronic applications. Among these, bismuth oxysulfide (Bi₂O₂S) has recently emerged as a candidate owing to its wide bandgap, low effective electron mass, and environmental stability. This review summarizes the synthesis strategies and device applications of 2D Bi₂O₂S. It systematically analyzes recent advancements in synthesis methodologies, ranging from scalable solution-based synthesis to back-end-of-line compatible, low-temperature metal–organic chemical vapor deposition. Furthermore, defect engineering, particularly through oxygen-vacancy control and doping, is discussed as a strategy to modulate the electronic band structure, enhance broadband nonlinear optical properties, and accelerate the photocarrier relaxation kinetics of 2D Bi₂O₂S. These tunable characteristics have enabled 2D Bi₂O₂S to be employed in electronic and optoelectronic devices. The review, therefore, discusses recent developments in device applications of Bi₂O₂S, including field-effect transistors, broadband photodetectors, and flexible photoelectrochemical sensors. Finally, the remaining challenges, such as wafer-scale single-crystal growth and reliable p-type doping, and future research directions are discussed for integrating Bi₂O₂S into three-dimensional integrated circuits and neuromorphic computing. Full article

Terahertz (THz) radiation generated through ultrafast transient photocurrent mechanisms has become a cornerstone of modern THz photonics, enabling broadband coherent emission with sub-picosecond temporal resolution. This review provides a comprehensive and mechanism-driven analysis of THz pulse generation via photo-Dember diffusion currents, surface depletion field acceleration, and biased photoconductive antenna architectures. We present a comprehensive comparative analysis of wide- and low-bandgap material platforms, including III–V, II–VI, and group IV semiconductors, as well as two-dimensional materials, topological insulators, and Weyl semimetals, highlighting how their intrinsic properties, such as band structure, carrier mobility, recombination dynamics, doping, and dielectric response, govern their THz emission efficiency, bandwidth, and spectral tunability. Special emphasis is placed on germanium (Ge), which has re-emerged as a highly promising THz source material owing to its high carrier mobility, long diffusion lengths, strain-tunable band structure, and CMOS compatibility. We highlight the roles of doping, strain-induced direct transitions, and several fabrication techniques in controlling the nonlinear photoexcited charge-carrier dynamics in Ge, thereby unlocking enhanced broadband THz performance. Finally, we explore the emerging application prospects of THz radiation, ranging from non-invasive security screening to biochemical sensing and archeological preservation. By bridging fundamental material science with scalable device architectures, this review outlines current challenges, highlights evolving opportunities in novel materials, and charts future directions towards integrated THz technologies. Full article

Developing lead-free organic-inorganic hybrid metal halides with strong light-harvesting capabilities and superior stability, while precisely tuning their crystalline phases and electronic structures, remains a key challenge in optoelectronics. Herein, we report a neutral iodine-induced structural transition from a 1D chain-like (C₆H₁₁NH₃)₂SbI₅ architecture to a 0D dimeric (C₆H₁₁NH₃)₃[Sb₂I₉]·I₂ supramolecular host-guest complex. This transformation is achieved via a controlled solution-cooling crystallization process, yielding high-quality bulk single crystals. Crystallographic analysis reveals that N–H···I hydrogen-bonding networks stabilize the organic cations, while halogen bonding interactions anchor the I₂ guests within the lattice cavities of the [Sb₂I₉]³⁻ dimeric host. Experimental characterizations, including XRD, TGA, and XPS, confirm the high phase purity and thermal stability of the (C₆H₁₁NH₃)₃[Sb₂I₉]·I₂ hybrid and determine its electronic band structure. To further elucidate the underlying mechanisms, theoretical calculations were performed, revealing that strong sp-orbital hybridization yields a high absorption coefficient. The associated dimensional transition narrows the direct optical bandgap to 1.46 eV, approaching the Shockley-Queisser limit and demonstrating strong potential for visible-light harvesting. This work elucidates the role of supramolecular host-guest interactions in modulating the lattice evolution of lead-free antimony-based materials, presenting halogen guest engineering as an effective approach for optoelectronic material design. Full article