With the increasing demand for low-resistivity substrates, growing heavily doped 4H-SiC crystals is emerging as a critical practice. Now, we report the growth of heavily nitrogen-doped, nitrogen-aluminum (N-Al) co-doped and nitrogen-gallium (N-Ga) co-doped 4H-SiC crystals by using the physical vapor transport (PVT) method. Comparative study shows that co-doping contributes to enhanced nitrogen incorporation efficiency and leads to lower resistivity. In addition, it is found that the heavy doping shifts the Fermi level of 4H-SiC into the conduction band. The temperature dependence of the mobility of heavily co-doped 4H-SiC indicates a thermally activated transport for electrons at temperatures above 300 K. Ga and Al atoms are found to effectively impede the glide and multiplication of basal plane dislocations (BPDs), reducing the density of BPDs. The N-Ga co-doping effectively suppresses the formation of stacking faults.
In this work, we demonstrate an Al-rich AlGaN channel metal insulator semiconductor HEMT device operating at >2 kV on a sapphire substrate. Devices with 2and 2.6 kV breakdown voltage demonstrated a Baliga figure of merit (BFOM) of 288 and 325 MW/cm(2) with an on-resistance of 14.15 and 21.02 m Omega.cm(2), respectively. Reported BFOM of 325 MW/cm(2) value is 1.7 times the state-of-the-art passivated AlGaN channel transistors on sapphire substrate. The obtained results represent the potential of the ultra-wide bandgap (UWBG) AlGaN channel transistors for advanced power electronics applications.
Lattice and microstructural phases are always critical for controlling optical, electronic, and optoelectronic characterizations of semiconductor materials and their functional devices. Gallium oxide (Ga2O3) is widely recognized as a promising material for solar-blind ultraviolet photodetectors, with both amorphous and crystalline phases offering distinct advantages. Nevertheless, inherent crystallinity issues still hinder device performance and practical application. In this work, we systematically investigated the correlation between microstructure and dynamic evolution of photogenerated carriers in Ga2O3 via crystal phase manipulation. High-performance nanocrystalline Ga2O3 photodetectors were demonstrated with a high detectivity of 3.50 & times; 1013 Jones and a larger photo-to-dark current ratio up to 5.56 & times; 104. Related photoresponsivity and rejection ratio of the ultraviolet photodetectors were significantly modulated by amorphous, nanocrystalline, and multicrystalline microstructural phases. This modulation is attributed to oxygen-vacancy-related defects, which introduce additional energy levels acting as electron donors that significantly alter the carrier concentration and thus regulate the signal intensity of the photoresponse. These insights underscore the critical role of structural phase engineering in Ga2O3 and provide valuable guidance for the design and optimization of high-performance solar-blind ultraviolet photodetectors.
Fluorescent antennas (FAs) based on quantum dots (QDs) are promising light-converting structures for optical wireless communication (OWC) owing to their high photoluminescence efficiency and ultrawide field of view (FOV). However, their stability is limited by degradation from water and oxygen, hindering long-term operation. Here, we present a strategy that combines a cross-linked resin with digital light processing (DLP) 3D printing to fabricate structurally programmable and environmentally robust FAs. The approach enables uniform QDs dispersion, high-resolution geometries, and tunable device architectures beyond conventional mold-based methods. Guided by Monte Carlo simulations, we further developed an encapsulated fluorescent antenna (EFA), in which the emissive QDs layer is fully enclosed in a transparent resin shell. This design provides effective isolation from moisture and oxygen while functioning as a low-loss optical waveguide. The optimized EFA achieved a side-emission efficiency of 10.9% and a wide FOV of 150 degrees. Importantly, the EFA retained over 70% of its emission intensity after 10 days in water. In the communication tests, the EFA demonstrated a 26 MHz modulation bandwidth and a 135 Mbps data rate. These results establish DLP-printed EFA as a versatile and stable platform for next-generation underwater photonic communication devices.
Li-S batteries possess an ultrahigh theoretical specific capacity of 1675 mAh g-1, yet their practical application is still hindered by the shuttle effect and sluggish sulfur redox kinetics. Current research on Li-S batteries mainly focuses on interface engineering strategies, while a systematic understanding of how the built-in electric field (BIEF) induced by work function mismatch regulates interfacial charge redistribution and sulfur-species conversion remains limited. In this work, we constructed a Co@NC Mott-Schottky heterojunction to induce interfacial charge redistribution. Experimental and theoretical results demonstrate that work function mismatch between the two phases also drives the spontaneous formation of a BIEF, which accelerates the bidirectional redox kinetics of sulfur. This BIEF drives the directional migration of interfacial charges and modulates the energy barriers of sulfur species conversion. Consequently, the Co@NC/S cathode delivers a high capacity retention of 82.1% after 400 cycles at 5 C, and retains 77.2% after 120 cycles under high sulfur loading (5.6 mg cm-2) and lean electrolyte conditions (E/S = 4.0 mu L mg-1). This work reveals the critical role of BIEF in boosting sulfur electrochemistry and provides a transferable interface engineering design strategy for high-performance Li-S batteries.
This paper presents a graphene-based terahertz absorber. Five narrowband absorption peaks are achieved at 2.82, 4.91, 6.53, 8.05, and 8.99 THz, with an average absorption rate of 96.56%. The device exhibits polarization-insensitive characteristics, maintaining stable absorption performance over incidence angles ranging from 0 degrees to 60 degrees. Dynamic tuning of the absorption peak frequencies is achieved by modulating the graphene Fermi level, and a five-frequency synchronous optical switching functionality is demonstrated, achieving a modulation depth up to 95.95% and insertion loss as low as 0.013 dB. In sensing applications, the device demonstrates highly sensitive responses, with a maximum sensitivity of 2.0 THz/RIU. Through systematic mechanism analysis, it provides a novel approach for terahertz functional devices that combines practical utility with manufacturability.
Reconciling a high magnetoelectric (ME) coupling coefficient with low noise levels in PZT/Metglas sensors remains a significant challenge. This study methodically examines the impact of Metglas layer count on the performance and magnetic loss mechanisms of sensors consisting of multiple Metglas layers and a single PZT-5H layer. Experimental results demonstrate that layer count significantly influences resonant frequency and DC bias dependence, with the latter caused by the magnetic flux shielding effect. The 5-layer Metglas configuration exhibits the most favorable overall performance, with the magnetoelectric coupling coefficient () attaining 415 V/(cm & centerdot;Oe) (8.3 & times; 104 V/T), limit of detection (LOD) as low as 25 pT. Furthermore, this configuration maintains a stabilized flat noise in the non-resonant region at . This work establishes a theoretical and experimental foundation for designing high-sensitivity, low-noise ME sensors for weak magnetic field detection.
In the infrared band, numerous substances show distinct absorption spectral line features. This characteristic can be utilized for spectral analysis of different objects. Because of the subwavelength structure and tunable properties of metamaterials, a broadband mid-infrared absorbing material with a surface metal cross-array structure is designed in this article. The substrate is metallic Ti, the middle layer is a Ti-ZnSe stack, and the top cross-array structure is metallic Ti. This absorber architecture exhibits a remarkable average absorption efficiency of 96.14% throughout the wavelength spectrum spanning from 7.23 to 21.49 mu m. Through a detailed analysis of electromagnetic field distributions at the resonant peaks, the physical mechanisms underlying the realization of broadband high absorption are systematically investigated. Finally, the spectral response of this structure under TM/TE mode and oblique incidence of the source is analyzed. The results highlight the superior absorption performance with compelling experimental evidence remains unchanged at large incident angles. This structure has wide applications in molecular imaging, infrared stealth, infrared detection, thermal radiation sources, and gas sensing.
GaN-based spin light-emitting diodes (spin-LEDs) are attractive for realizing room-temperature spin-controlled light emission in efficient, color-tunable devices. In this work, we demonstrate spin injection in a GaN spin-LED fabricated on a Si substrate using wafer-bonding technology. An inverted n-i-p LED structure with n-type GaN on top facilitates the injection of spin-polarized electrons from a ferromagnetic Au/Co/MgO spin-injector layer grown by molecular beam epitaxy. At room temperature, an electroluminescence circular polarization of approximately 8% is measured under an applied 1 T out-of-plane magnetic field in a surface-emitting geometry. After considering contributions from the Zeeman effect and magnetic circular dichroism, about 6% circular polarization is attributed to the pure spin injection into GaN. This work is focused on the detailed structural and interface characterization of the spin-LED and allows to understand its spin and optoelectronic properties. These results highlight the potential of GaN-based spin-optoelectronic devices compatible with Si platforms.
Dion-Jacobson (DJ) phase halide perovskites have garnered significant attention in photoluminescence applications due to their excellent stability compared to three-dimensional (3D) perovskites. However, in solution-processed DJ-phase perovskite films, the complex crystallization process and the formation of multi-dispersed quantum well structures significantly impact the optoelectronic properties of the DJ-phase perovskite. This work presents a quasi-two-dimensional (quasi-2D) mixed-phase perovskite (MPP) film by introducing Ruddlesden-Popper (RP)-type aromatic ammonium cations into the DJ-phase precursor. The resulting MPP0.2 film, with the chemical formula (PEA2)0.2HDA0.8FA7Pb8Br25 (where HDA = hexamethylenediammonium and PEA = phenylethylammonium), exhibits improved morphology, a more uniform distribution of n phase components, higher crystallinity, and enhanced hydrophobicity compared to the neat DJ-phase films. Notably, the amplified spontaneous emission (ASE) threshold of the quasi-2D MPP0.2 film decreased from 120 to 60 mu J/cm2. This research shows that quasi-2D MPP films have great potential as waveguide materials for stable, low-threshold ASE.
Crystalline Mn1Sb2Te4 (MST), an intrinsic magnetic topological insulator, shows similarity to the ground-s tate structure of the phase-c hange alloy Ge1Sb2Te4 (GST). However, the atomic structure and key physical properties of amorphous MST-crucial for phase-c hange functionality-have not been reported to date. In this work, we investigate the amorphous and crystalline states of MST using density functional theory (DFT) and DFT-b ased ab initio molecular dynamics (AIMD) simulations. In addition to the ordered trigonal phase, we predict the existence of a metastable cubic rocksalt-l ikephase with a high concentration of intrinsic cation vacancies, in close analogy with rocksalt-l ike GST. Structural analysis reveals that the short-r ange order in amorphous MST resembles that of the rocksalt-l ike phase, featuring defective octahedra and abundant four-m embered rings. Furthermore, MST maintains spin polarization in both amorphous and crystalline phases and exhibits a contrast in magnetic and optical properties. These findings identify MST as a promising candidate for applications combining phase-c hange functionality with intrinsic magnetic order.
Insulator-to-metal transitions in (V1-xCrx)2O3 Mott materials can be triggered by adjusting temperature, pressure, and Cr content. Beyond these conventional routes, the insulating phases of these compounds also display an out-of-equilibrium insulator-to-metal transition under electric pulses, associated with the formation of a percolating metallic pathway within an insulating matrix. This resistive-switching property holds promise for emerging devices, such as nonvolatile memories and artificial synapses or neurons. However, understanding the microscopic nature of the electrically induced metallic state remains a key challenge. Electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM) is demonstrated here as a sensitive and spatially resolved technique for distinguishing metallic and insulating domains in (V1-xCrx)2O3 Mott systems at the nanoscale. Studies on single crystals reveal the existence of a 0.25 eV shift in volume plasmon energy between the paramagnetic metal (PM) and the insulating phases-paramagnetic insulator (PI) and antiferromagnetic insulator (AFI). This shift arises from the unit cell volume expansion occurring at the metal-to-insulator transition, which decreases the density of valence electrons. It is further demonstrated that this nanoscale characterization approach can be effectively extended to polycrystalline V2O3 thin films and to memory devices based on (V1-xCrx)2O3.
Herein, highly crystalline, well-dispersed Mn2+-doped CsPbCl3 perovskite quantum dots (PQDs) were synthesized via the hot-injection method, and their down-conversion luminescent properties were optimized by adjusting the Mn2+ doping concentration. Upon excitation with 365 nm UV light, CsPbCl3:Mn PQDs show bright orange luminescence at approximate to 600 nm, which is ascribed to the 4T1 -> 6A1 transition of Mn2+ ions. An ultrasonic spray coating technology is introduced to fabricate flexible, high-performance down-conversion film based on PQDs embedded in ethyl cellulose (EC) polymer matrix. The as-prepared composite film exhibits a dense, uniform, crack-free morphology and a smooth surface. EC polymer significantly improves the environmental stability of CsPbCl3:Mn PQDs. Mn2+ emission intensity of CsPbCl3:Mn@EC film could retain 67.8% of its initial value after 20 mins of water immersion, and more than 90% of the initial value after continuous exposure to ambient air for 40 days. When these PEQs are applied as a down-conversion layer of Sb2Se3 solar cells, it significantly enhances the external quantum efficiency values in the ultraviolet region (250-360 nm). This work demonstrates that ultrasonic spray coating enables large-scale production of high-quality perovskite films, providing a novel type of high-performance down-conversion layer material in fields such as flexible optoelectronic devices.
We propose a novel topological laser design based on the Su-Schrieffer-Heeger (SSH) model that enables dynamically tunable domain walls through modulation of intra-cell and inter-cell coupling coefficients. By incorporating artificial gauge fields to control coupling phases, domain walls can be precisely positioned, overcoming the fixed-position limitation in conventional systems. We develop a domain wall dynamics model using laser rate equations and demonstrate that selective pumping at domain wall positions provides enhanced topological protection compared with uniform pumping schemes. Numerical simulations confirm robust single-mode lasing with controllable emission locations.
Arsenic-free ovonic threshold switch (OTS) materials are important for enabling sustainable selector devices in high-density crossbar memory arrays. Guided by ab initio design, we investigate Si-doped GeS2 as a promising candidate, offering improved thermal stability and reduced leakage compared to alternative arsenic-free materials. Thin films with up to 10% Si content were deposited by cosputtering and demonstrated thermal stability above 500 degrees C. Device electrical characterization revealed good IOFF performance comparable to reference SiGeAsSe devices. These results position Si-doped GeS2 as a viable candidate for environmentally friendly, arsenic-free OTS selectors, with further optimization needed to address endurance limitations.
Owing to their unique structural and electronic properties, transition metal dichalcogenides have recently attracted significant attention for advanced electronic device applications. In this study, we report the first investigation on the resistive switching behavior of MnTe2-based device with a W/MnTe2/W structure, in which tungsten is employed as a passive electrode to suppress undesired electrode reactions. The device exhibits both volatile and nonvolatile resistive switching behaviors, demonstrating the versatility of MnTe2-based device. The nonvolatile resistive switching behavior is attributed to the formation and annihilation of voids driven by thermally assisted electromigration of Mn and Te ions. Furthermore, Te clustering near the electrode interface gives rise to a self-selective behavior, which may eliminate the need for an external selector in three-dimensional cross-point architectures.
In this study, a novel atomic structural analysis of the addition of copper (Cu) atoms into NiTi shape memory alloys (SMAs) was successfully performed using molecular dynamics simulations. The interatomic interactions were modeled using the Embedded Atom Method (EAM) potential, and the simulation results were compared with available experimental data. The atomic structural characteristics were evaluated through radial distribution functions (RDF), structure factors S(q), and local atomic structure analysis. The results indicate that the incorporation of Cu atoms into the NiTi alloy alters the atomic packing density, as reflected by changes in the first peak intensity of the radial distribution functions (RDF) and structure factors S(q). Furthermore, variations were observed in the populations of local structures, including body-centered-cubic (bcc), face-centered-cubic (fcc), hexagonal-close-packed (hcp), and icosahedral (ico) configurations; however, these changes were not significant.
The electronic structure, magnetic properties, and external-field modulation behavior of the Janus MXene CrScCO2 aresystematically studied via density functional theory (DFT + U) and HSE06 calculations. Hubbard U parameters are set to U Cr = 3.5 eV and U Sc = 0 eV based on systematic tests of their effects on electronic and magnetic properties. At equilibrium, DFT+U calculations suggest a nearly gapless state (approximately 0.016 eV). In contrast, the more accurate hybrid functional HSE06 yields a small but finite band gap of 0.677 eV, confirming the semiconducting nature of the ground state. This quantitative difference reflects the distinct treatments of electron correlation. More importantly, regardless of the quantitative method-dependence, the band structure of CrScCO2 proves to be highly tunable by external fields. Both strain and a vertical electric field can effectively modulate and even close this gap, driving the system into half-metallic and, crucially, spin-gapless semiconductor (SGS) states. This demonstrates that although CrScCO2 exhibits a moderate band gap at the hybrid functional level, its electronic structure is susceptible to external perturbations, enabling a transition into the SGS regime under appropriate modulation. This material demonstrates good thermal stability at room temperature, showing potential as a tunable functional material in low-power spintronic devices.
The combustion of fossil fuels leads to excessive CO2 emissions, triggering global warming and energy crisis. Electrocatalytic CO2 reduction (eCO2RR) offers a feasible way to convert CO2 into high-value-added chemicals. Extensive investigations have been made on Cu-based catalysts, which have been proven to be highly efficient in eCO2RR; however, deviations exist, i.e., different potentialdetermining steps (PDS) obtained from theoretical and experimental results. We show that the PBE + D3/M06 hybrid computational scheme of Araujo et al. (Nature Communications, 2022, 13, 6853) that combines periodic PBE + D3 structural optimization with cluster-model M06 energy corrections could match the eCO2RR experimental data on Cu based catalysts. It shows that for the eCO2RR on the Cu (100) surface, the PDS for methane formation is the *CO -> *CHO hydrogenation step. The limiting potential calculated by this method (0.81 eV) closely matches the experimental value (0.80 eV). We further use this method to predict the PDS on transition metal-doped Cu (100) surfaces to accurately predict PDS. This work confirms that PBE + D3/M06 provides a precise and efficient method to predict the experimental eCO2RR reaction process.
We investigate intermediate states of Ge-rich GeSbTe phase-change memory (PCM) cells by electrical impedance spectroscopy (EIS) after partial SET and RESET programming. The electrical impedance response is well described by a series resistor and a parallel RC circuit, allowing extraction of state-dependent resistance and capacitance values. A resistance ratio of similar to 250 and a capacitance reduction of similar to 85% are observed between RESET and SET states. While resistance can be continuously tuned, capacitance major variation remains confined near the SET state, with crystalline-dominated cells exhibiting the highest values. Technology computer-aided design simulations confirm the equivalent circuit and reveal that conduction mainly occurs along the amorphous-crystalline interface. Cells with embedded Ge or Sb grains display the largest capacitances, as these inclusions provide extra conduction pathways and localized charge storage sites that jointly influence the device's resistance and capacitance. Overall, this work demonstrates that the electrical properties of inhomogeneous multiphase PCMs are governed by the complex network of nanoscale heterostructures present in their active regions. It also demonstrates that EIS is a suitable, nondestructive technique for characterizing PCM devices.
