Physics

We demonstrate a facile method to produce blue-emitting InP quantum dots (QDs) by a liquid-mediated femtosecond laser ablation in liquids (FLAL) technique. Various complementary characterizations confirmed the formation of InP nanoparticles in toluene with an average size of ∼11 nm, comparable to the Bohr exciton radius of InP (∼10 nm). An exotic high-pressure stable phase of the InP (cubic-zinc blende) is observed in the core region of the formed nanoparticles, whereas a metastable phase, such as hexagonal InP with a wurtzite structure, is observed in the edge region. The broad and intense emission observed near 400 nm is attributed to the confinement effects. Interestingly, the FLAL of InP in de-ionized water and acetone led to the formation of In2O3 and other InP-based composite nanoparticles. The important role of solvents in the production of diverse InP QDs has been discussed in detail, especially considering their polar and protic nature. The ablated surfaces have also exhibited distinct nanostructures in all three cases. These results illustrate beneficial information for the controlled production of InP-based quantum dots and to elucidate the underlying phenomenon governing the ultrafast ablation of semiconductors in liquid media.

The performance-limiting electron and hole trapping centers in 4H-SiC PiN power diodes are determined by combined deep-level transient Fourier spectroscopy (DLTFS) experiments and technology computer-aided design (TCAD) simulations. Two electron traps E1 (EC − 0.19 eV) and E2 (EC − 0.67 eV) and three hole traps H1 (EV + 0.16 eV), H2 (EV + 0.3 eV), and H3 (EV + 0.63 eV) are detected by DLTFS. Since DLTFS measurements were limited to 400 K, a few deep-level defects could not be detected in our experiments. In addition to the traps identified by DLTFS, two deep levels commonly reported at elevated temperatures, E3 (EC – 1.65 eV) and H4 (EV + 1.43 eV), are integrated into the TCAD model to perform a reliable trapping analysis. The effects of electron traps, hole traps, and individual traps are evaluated by selectively excluding them from the simulation. Hole trapping is found to be more prominent than electron trapping in pristine (as-fabricated/untouched) diodes. Among the traps, shallow hole trap H1 exhibits a strong impact in reducing the conduction current (followed by E3) in pristine diodes. To explore the fundamental nature of each trap, the concentration (NT) of an individual trap is increased to a higher value without changing the NT of other defects. Subsequently, the diode characteristics are analyzed at higher NT of the specific trap. The traps E2 and E3 significantly reduce the diode current at higher NT. The deep acceptor E2 is primarily responsible for the donor doping compensation in the n− drift layer.

High-frequency ultrasonic sensors exhibit outstanding spatial resolution in biomedical imaging and micro-scale, non-destructive testing. However, their performance is constrained by severe acoustic impedance mismatch between the piezoelectric layer and the propagation medium, resulting in low sensitivity and limited operating bandwidth. The quarter-wavelength theory is the most traditional method for acoustic impedance matching, but it is difficult to achieve both a specific acoustic impedance and precise thickness control at the same time. This paper proposes and experimentally validates a dual-layer acoustic impedance matching strategy for self-focusing ZnO high-frequency ultrasonic sensors. The matching structure comprises a low-impedance parylene layer and a high-impedance molybdenum metal layer. Their thicknesses were jointly designed using a mass-spring model and microwave transmission line theory and then optimized through finite element simulation. Using chemical vapor deposition and ion beam sputtering, the bilayer matching film was conformally deposited onto the sensor's focusing surface, demonstrating the feasibility of this bilayer structure on non-planar high-frequency devices. Pulse-echo testing revealed that the introduction of the dual-layer matching structure increased the sensor's peak-to-peak echo voltage from 320 to 751 mV (a 135% improvement) and expanded the −6 dB bandwidth from 60.49% to 87.27%. The results demonstrate that the synergistic effect of impedance gradient transition and mass-spring resonance enhancement simultaneously improves sensitivity and bandwidth. This study provides a novel acoustic matching scheme for high-performance self-focusing high-frequency ultrasonic sensors and, for the first time, extends multilayer matching technology from planar devices to self-focusing high-frequency devices.

This study investigates the nonlinear behavior of asymmetric radio frequency (RF) discharges at high pressures implemented in a compact coaxial connector geometry, with a particular focus on sheath dynamics. We present a novel experimental approach that enables accurate, non-intrusive measurements of the temporal evolution of voltage and current waveforms. The experimental results reveal strongly nonlinear, anharmonic current waveforms, while driving voltage is kept nearly sinusoidal in the experiments. Increasing the pressure increases from 10 to 40 Torr leads to stronger anharmonicity in the current response. Furthermore, we demonstrate that a simple theoretical model, representing the RF discharge cell as a time-varying capacitor associated with the oscillating sheath near the central discharge electrode, closely matches experimentally measured voltage and current waveforms. The measured plasma capacitance shows strong agreement with theoretical predictions, thereby validating the model. Fast Fourier transform analysis confirms a substantial rise in the second harmonic amplitude at higher pressures and frequencies, highlighting the growing role of nonlinearities. These findings have significant implications for plasma capacitors and reconfigurable RF devices, where controlling nonlinearity is crucial for optimizing circuit performance. This study extends the operational understanding of RF plasmas to higher pressures, bridging the gap between low-pressure theoretical models and practical high-pressure applications.

We conduct a statistical analysis of the grain boundary structure of undoped polycrystalline silicon films. We study the effect of thickness on the formation of grain boundary structure in undoped polycrystalline silicon films using transmission electron microscopy and atomic force microscopy. The fibrous structure observed in films obtained by low-pressure chemical vapor deposition indicates the leading role of twinning processes in the formation of this type of structure in silicon films. We analyze the mechanism of twin complex growth and find that various types of triple and multiple grain boundary junctions are observed in silicon films with a fibrous structure; the ratio of these junctions is determined by the film thickness. The formation of the different junction types is associated with the mechanisms of film growth. Our analysis of the experimental data shows that the formation of multiple grain boundary junctions in the films is due to processes such as multiple twinning, splitting of grain boundaries, and random meeting of several twin boundaries of the Σ3n type. The obtained results are important for the investigation of defect behavior and the development and fabrication of nano-scale systems using undoped polycrystalline silicon films.

AlGaN/GaN metal–insulator–semiconductor-high electron mobility transistors (MIS-HEMTs) with identical size parameters were fabricated using Si3N4 and ZrO2 as gate dielectrics, which have different relative permittivities. Based on experimental data and the Polarization Coulomb Field (PCF) scattering theory, the correlations among the additional polarization charges (ΔρG), the two-dimensional electron gas (2DEG) mobility, and the parasitic resistances (RS and RD) were quantitatively analyzed. This study reveals the underlying mechanism by which the gate dielectric relative permittivity modulates the PCF scattering and the electrical performance of the device. The results demonstrate that a higher gate dielectric relative permittivity alters the voltage partition between the dielectric layer and the AlGaN barrier. This alteration intensifies the vertical electric field within the barrier layer and induces more significant strain via the inverse piezoelectric effect. Consequently, a larger amount of ΔρG are generated, which notably reduces the under-gate electron mobility and modulates parasitic resistances. The enhanced PCF scattering further exacerbates the asymmetry of electron mobility in the source and drain access regions, resulting in an enlarged difference between per-unit-length values of RS and RD. This work provides a theoretical basis for the gate dielectric engineering of high-performance GaN-based MIS-HEMTs.

The room-temperature dispersive refractive indices of GaSb and GaSb-matched AlAs0.08Sb across the 2–4.15 μm range are determined by a new approach to the analysis of interference fringes in reflectance spectra. This method utilizes linear regression of interference fringe positions over various oblique angles of incidence to remove the need for measurements to be taken at normal incidence. The presented refractive indices are validated by simulation of the reflectance spectrum of a distributed Bragg reflector. An alternative method is also presented, suitable for characterizing epilayers with low film thickness, such as those intended for epitaxial growth calibration. In such thin films, fewer interference fringes form within a given spectral range, prohibiting analysis by the primary method. The alternative method is applied to thin films of GaSb-matched GaInAsSb, extracting the dependence of the room-temperature static refractive index on increasing indium content.

Freezing shrinkage is an inherent phenomenon for liquid alloys and becomes particularly critical in a space microgravity environment, where the suppression of natural convection and the absence of container walls fundamentally alter the solidification process. To clarify the governing mechanisms, containerless rapid solidification experiments are conducted aboard the China Space Station under controlled undercooling conditions. By combining measured thermophysical properties with calculated internal flow velocities, both the phase-transition volume contraction and the liquid feeding capability are quantified during solidification. A new dimensionless shrinkage criterion is established by comparing these two competing effects, enabling the evaluation of local shrinkage risk. The criterion successfully predicts shrinkage risk across different undercooling levels and shows strong agreement with experimental observations. This work provides a practical framework for assessing shrinkage behavior in microgravity and supports the development of defect control in future space-manufactured materials.

Conventional metasurfaces encounter two limitations in applications such as 5G/6G wireless communication systems and intelligent radomes. One limitation is the large unit size, which hinders integration with compact electromagnetic devices. The other is the fixed frequency response, which limits adaptability to dynamic and complex electromagnetic environments. To overcome these challenges, we propose a miniaturized reconfigurable metasurface design capable of tunable passband/stopband responses in dual-band. The metasurface employs a cascaded structure combining hybrid resonators with impedance controllers. The hybrid resonators feature specially designed convoluted metallic patterns to reduce the unit size while preserving filtering performance. As a result, the unit size is minimized to 0.041λ0 for the metasurface (where λ0 is the wavelength at the center frequency of the first passband). Experimental results demonstrate that the structure operates at 1.55 and 3.32 GHz, with a stable response under oblique incidence angles of up to 45°, demonstrating its reconfigurability under various polarization states and incident conditions.

Superconducting Magnetic Energy Storage (SMES) systems exhibit significant potential in smart grid and high-dynamics energy storage applications due to their high-power density and rapid response capabilities. This work examines the multi-field coupling behavior of No-Insulation (NI) high-temperature superconducting coils, specifically analyzing their performance evolution during charging and under harsh operational conditions. A 2D axisymmetric multi-physics coupling model of the NI magnet coil was established using an improved lumped equivalent circuit model and T–A formulation under Neumann boundary conditions. The model analyzes the electromagnetic losses, temperature distribution, and mechanical response characteristics under different excitation rates and sudden power-down events. The results demonstrate that an elevation in excitation rate markedly intensifies the angular current delay effect and radial current redistribution, resulting in a large increase in the coil's total electromagnetic losses and temperature. In the event of a sudden power-down, the induced terminal voltage experiences a reverse surge (−15.322 mV), causing a sharp increase in electromagnetic losses. The NI coil effectively mitigates transient loads through a radial current redistribution mechanism. Mechanical analysis indicates that under high-speed excitation, the uneven distribution of shielding currents leads to circumferential stress concentration at the inner radius of the top coil, resulting in turn-to-turn lamination at the unconstrained outer radius and thereby reducing the mechanical performance of the coil. This study reveals the self-carrying operational characteristics of the NI coils under multi-field coupling, providing novel perspectives on the design and application of NI coils in SMES systems.

Magnetic van der Waals (vdW) layered materials have emerged as a research hotspot in condensed matter physics over the past decade. These materials not only exhibit rich physical properties but also provide promising candidates for next-generation magnetic functional devices. For practical applications, the Curie temperature (TC) is a critical performance metric, as it determines the upper limit of the device operating temperature. To date, only a limited number of vdW magnets have been experimentally reported to possess TC above room temperature. Among them, Fe3GaTe2 (FGaT) stands out with a TC of up to 350 K. A substantial enhancement of its TC via compositional modification would not only broaden the working temperature window but also improve functional stability under ambient conditions. Here, density functional theory calculations are employed to construct a Li-intercalated FGaT lattice model, denoted as Li-FGaT, and to study the magnetism enhancement induced by Li-ion intercalation. Our results predict a significantly improved TC of 770 K for Li-FGaT. It is revealed that the electron doping introduced by Li-ion intercalation not only provides interfacial spin-polarized mediating carriers to strengthen the interlayer ferromagnetic coupling but also induces intralayer electron redistribution to enhance the spin exchanges, leading to elevated TC. Thus, this work provides a testable target for experiments and offers useful insights into the development of high-TC vdW magnets.

Photoluminescence (PL) from Be-implanted GaN containing a high concentration of oxygen was investigated. The GaN crystals were grown along nonpolar crystallographic directions by hydride vapor phase epitaxy on ammonothermal substrates. After ultrahigh-pressure annealing, secondary ion mass spectrometry revealed box-shaped Be diffusion profiles, while the concentration of unintentionally incorporated oxygen exceeded that of Be. The dominant defect-related emission at low temperatures is the yellow luminescence band (YLBe), which is unambiguously attributed to isolated BeGa acceptors. The PL exhibits all characteristic features previously reported for Be-doped GaN, including two-step thermal quenching of the YLBe band, its abrupt redshift at T ≈ 100 K, and the emergence of the ultraviolet luminescence (UVLBe3) band at T > 150 K, associated with the shallow state of the BeGa acceptor. A pronounced orientation-dependent effect is observed at 100–120 K: the YLBe intensity increases in nonpolar GaN samples but decreases in polar (c-plane) GaN:Be. This behavior is explained by differences in light-extraction efficiency from polaronic dipoles with different orientations, providing strong experimental confirmation of the previously proposed BeGa acceptor model.

Self-Powered Flexible Triboelectric-Gated Ion-Gel Transistor This cover depicts a battery-free flexible neuromorphic system where biomechanical motion is directly translated into synaptic function. A triboelectric nanogenerator powers a graphene-channel ion-gel-gated transistor, while mobile ions represent analog memory storage. Human motion surrounding the device highlights self-powered tactile sensing, adaptive learning, and wearable activity recognition. More details can be found in the Research Article by Youngmin Lee, Sejoon Lee, and co-workers (DOI: 10.1002/adma.202520540).

Self-Powered Flexible Triboelectric-Gated Ion-Gel Transistor This cover depicts a battery-free flexible neuromorphic system where biomechanical motion is directly translated into synaptic function. A triboelectric nanogenerator powers a graphene-channel ion-gel-gated transistor, while mobile ions represent analog memory storage. Human motion surrounding the device highlights self-powered tactile sensing, adaptive learning, and wearable activity recognition. More details can be found in the Research Article by Youngmin Lee, Sejoon Lee, and co-workers (DOI: 10.1002/adma.202520540).

ABSTRACT Facing the challenge of achieving efficient and sustainable hydrogen peroxide (H 2 O 2 ) production, a promising strategy is developing highly selective electrocatalysts with controllable synthesis, structural design and performance optimization. Herein, an interfacial acid sites‐mediated ZnSe/ZnO heterojunction is synthesized for highly selective two‐electron oxygen reduction reaction (ORR) toward H 2 O 2 production. Experimental and theoretical results reveal that surface selenization induced reconstruction, forming a synergistic interface with a built‐in electric field and tailored oxygen vacancies (Ovs), which collaboratively optimize the electronic structure and accelerate reaction kinetics of two‐electron ORR. Moreover, interfacial unsaturated Zn 2+ sites and OVs served as Lewis acids sites to enhance O 2 adsorption and activation, while Br ø nsted acids sites were liable to donate protons to promote *OOH formation. Consequently, a ZnSe/ZnO ‖ ZnO flow cell enabled paired electrolysis for concurrent H 2 O 2 production with a high H 2 O 2 yield of 754.4 M g cat −1 over 12 h. A rechargeable Zn‐H 2 O 2 cell using ZnSe/ZnO cathode delivered a power density of 11.99 mW cm −2 as a self‐sustaining process for simultaneous on‐site H 2 O 2 production and electrical energy generation. This work offers a sustainable route for on‐site H 2 O 2 synthesis with improved energy efficiency, advancing green chemistry and circular economy.

The design of hydrogel-based artificial tissues capable of reversible, programmed, and complex motions requires both stimuli-responsiveness and structural anisotropy. In this work, non-unidirectional anisotropies are generated in biocompatible hydrogels by structuring magnetic particle suspensions into lamellar architectures through two distinct routes: the application of an unsteady magnetic field to a quiescent sample, and the superposition of a steady magnetic field with shear flow. In both approaches, magnetic particles undergo directed self-assembly within a polymer matrix that subsequently gels, thereby preserving the formed structures. We analyze the assembly kinetics, characterize the resulting lamellar patterns, and construct phase diagrams for each method. The morphology and periodicity of the lamellae are shown to depend strongly on geometric confinement, enabling tunable interlamellar spacing from tens to hundreds of microns. Crucially, it is demonstrated that the resulting layered hydrogels can confine human fibroblasts between adjacent particle-rich lamellae, maintain cell viability above 95% over 7 days of culture, and promote preferential cell alignment parallel to the layered structures. These findings establish magnetic field-directed lamellar structuring as a versatile route to anisotropic hydrogels with programmable internal architecture, opening new opportunities in tissue engineering, bioactuation, and soft robotics.

ABSTRACT Half‐Heusler (HH) compounds are promising thermoelectric (TE) materials, but their intrinsically high lattice thermal conductivity ( κ L ) limits TE performance. Here, we report sublattice softening‐induced intrinsically low κ L and exceptional thermoelectricity in the previously underexplored rare‐earth (RE) containing HHs. Unlike conventional non‐RE HHs, the softened RE‐based lattice framework in RE‐HHs enables vigorous atom vibration within the 4c sublattice, strengthening lattice anharmonicity and phonon damping. This effect can be further amplified when heavier elements occupy the 4c sublattice, effectively suppressing both acoustic and optical phonon propagation and resulting in a pronounced reduction in κ L . Leveraging the low κ L , we identify four RE‐HHs—DyPtSb, Y 0.7 Lu 0.3 PtSb, Sc 0.6 Lu 0.4 PtSb, and Dy 0.7 Y 0.3 PtSb—with peak zT values exceeding 1.0. Notably, Dy 0.7 Y 0.3 PtSb achieves a maximum zT of 1.33 at 875 K. These findings underscore the promising potential of sublattice‐softened RE‐HHs as highly efficient thermoelectrics with broad compositional tunability.

ABSTRACT Engineering electron transport layer (ETL) interface is critical for high‐efficiency and long‐term stability in inverted perovskite solar cells (PSCs), yet co‐assembled hybrid interlayer are rarely explored for this upper interface. This work integrates 4‐aminobenzoate acid hydrochloride (4AA) with a dibenzo‐18‐crown‐6 (DB18C6) to construct a hybrid interlayer at ETL interface. The 4AA molecules intercalate into DB18C6 aggregates, homogenizing the monolayer and boosting surface coverage (from 0.57 to 0.79) and strengthening the interfacial dipole moment (from 2 to 7 Debye). This interlayer provides dual passivation, in which the ─NH 3 + and ─COOH groups of 4AA neutralize ionic defects, while DB18C6 optimizes perovskite crystallinity and energy level alignment. Therefore, modified devices achieve an efficiency of 26.33% (exceeding 22.92% of the control) with high open‐circuit voltage (V OC ) of 1.167 V and fill factor (FF) of 86.05% (compared to 1.130 V and 80.38% of the control). More importantly, the co‐assembled hybrid interlayer serves as a barrier against environmental and ionic degradation. The unencapsulated device demonstrates outstanding operational stability, retaining 93.2% of initial efficiency after 1000 h of maximum power point tracking. This work demonstrates a co‐assembly strategy to address efficiency and stability challenges at ETL interface, paving a reliable path toward high‐performance and stable inverted PSCs.

Oxygen- and biological cue-deprived microenvironments formed during tissue regeneration severely limit cell survival and differentiation, resulting in long-term structural and functional deficits. However, conventional oxygen-releasing biomaterials often exhibit burst releases, with the vast majority of oxygen released during the first few days, which is associated with high levels of concomitant reactive oxygen species (ROS)-derived oxidative stress and a lack of bioactive factors. Here, we report a hierarchically engineered zein-ceria hybrid microparticle that enables sustained ROS-neutral oxygenation for over 40 days and supplies an osteoinductive factor. A hydrophobic zein core stabilizes the oxygen source and suppresses burst release, while a ceria nanozyme-integrated shell continuously scavenges excess ROS via redox cycling. Biocompatible surface engineering enables the seamless integration of these microparticles within stem cell spheroids, which markedly enhances cell survival under anoxia. Their biofunctional surface supports enzymatic protein immobilization under physiological conditions, enabling spontaneous osteogenesis of engineered bone microtissues. In a severely oxygen-deprived mouse calvarial defect model, the engineered microtissues accelerated bone regeneration. Our biomaterial design enables control of burst oxygen release, ROS modulation, and growth factor release, built on a zein-ceria double-layer architecture, offering a modular platform that broadens the utility of oxygenating and bioactive micromaterials in regenerative medicine.

H-aggregates offer intrinsic features for type I photodynamic therapy (PDT) by concurrently promoting triplet state formation and strengthening charge transfer ability. However, their exploitation remains limited by the inherently large absorption blueshift (usually >100 nm) arising from strong H-type excitonic coupling in conventional parallel-packed H-aggregates, forcing short-wavelength laser excitation with poor tissue penetration. Herein, this study reports a planarity-hindrance co-balance strategy to develop donor-π-acceptor-based antiparallel-packed H-aggregates with minimal absorption blueshift for type I PDT. The results demonstrate that π-bridge planarization drives H-packing, while donor-site steric tuning dictates the blueshift by modulating slipping angles and π-π overlapping degree, and a steric threshold (Me/OMe) is identified beyond which blueshift becomes invariant. The optimized MTBSIC molecules form H-aggregates with an exceptionally small blueshift of 15 nm over its monomers. MTBSIC H-aggregates further display markedly enhanced type I ROS generation and improved photothermal conversion ability over their amorphous counterparts possessing similar monomeric photophysical properties. Mechanistic analyses reveal that H-packing promotes both intersystem crossing and intermolecular charge transfer/separation, synergistically boosting type I ROS production. MTBSIC H-aggregates further achieve potent tumor inhibition with high biocompatibility both in vitro and in vivo. This work establishes a generalizable molecular design paradigm for near-monomer-like H-aggregates for high-performance phototheranostics.

ABSTRACT The global transition toward renewable energy and carbon neutrality has sharply increased the demand for energy‐storage systems with higher energy density, improved safety, and extended service life. Despite the dominance of lithium‐ion batteries, their development is greatly limited by the flammability and electrochemical instability of liquid electrolytes. Solid‐state lithium batteries (SSLBs) provide a promising alternative because solid‐state electrolytes (SSEs) eliminate electrolyte leakage, enhance thermal stability, and enable the use of high‐voltage cathodes and lithium‐metal anodes. Among candidate cathode materials, high‐nickel layered oxides (LiNi x Co y Mn 1‐ x ‐ y O 2 , x ≥ 0.8) are the most viable for practical deployment, owing to their high specific capacity, moderate cost, and industrial maturity. However, their integration with SSEs introduces severe challenges, including structural degradation, oxygen release, and interfacial instability, which collectively impede lithium‐ion transport and compromise cycling durability. This review summarizes recent progress in SSLBs with high‐nickel cathodes, focusing on (1) structural and surface engineering of high‐nickel cathodes, (2) optimization of oxide‐, sulfide‐, halide‐, and polymer‐based SSEs, and (3) interface‐engineering strategies, including buffer layers and in situ interfacial design. Finally, perspectives are provided on material innovation, interfacial characterization, and scalable manufacturing, aiming to guide the development of next‐generation SSLBs that combine high energy density with intrinsic safety.