Device Applications Research Articles

Layer-by-layer assembled aramid nanofiber/MXene aerogel: Exceptional resistance to extreme temperatures and robust anisotropy for advanced applications

Aerogels are characterized with unique morphology and physical properties, thus are serving as essential elements in advanced applications. Nowadays, the delicate intelligent devices are frequently exposed in harsh environments, leading to multiple issues during application of functional aerogels including the limited resistance to extreme temperatures, requiring encapsulation prior to usage, and accumulation of Joule heat. In this study, we fabricated a multilayered aramid nanofiber (ANF)/MXene aerogel with the layer-by-layer stacking ANF and ANF/MXene layers. Attributing to the multilayered and porous structure, the aerogel displayed proper EMI shielding performance which maintained stable in harsh environments of excessive high temperature (200 °C) and low temperature (−196 °C). More importantly, obvious anisotropy in electrical conductivity (∼8 orders of magnitude) and thermal insulation (ΔT = 32 °C) was obtained along the in-plane and out-of-plane directions. As two demonstrations of potential applications, the sensing performance and thermal insulating property of the ANF/MXene aerogel was displayed. Inspiringly, the aerogel sensor exhibited significant durability and notable sensitivity to different deformations. Also, the aerogel displayed rapid heat dissipation along the in-plane direction while efficient thermal insulation along the out-of-plane direction, thus, can be applied in thermal management to protect the electronic devices. Therefore, the as-prepared ANF/MXene aerogel can serve as EMI shielding parts, encapsulation-free flexible electronics as compression sensor and anisotropic thermal insulator, which has great potential in the application of intelligent devices.

Recent Advances of Photodetection Technology Based on Main Group III–V Semiconductors

AbstractThe rapid advancement of main group III–V nanomaterials endows photodetectors (PDs) with enhanced performance. At present, various III–V nanomaterials are systematically investigated, whereof III–V semiconductors have attracted a successively increased attention that calls for a comprehensive summary which also can define the state‐of‐art for their further development. Herein, this work systematically introduces and discusses key aspects of the field. First, the advanced strategies for the preparation of III–V semiconductor materials and the device structures of the subsequent PDs based on these materials, pristine and doped, are addressed. The focus is then turned to their performance under the irradiation of various wavelengths, separately summarizing and comparing the photodetection properties under infrared, UV and visible light. Finally, challenges and future perspectives of III–V semiconductor‐based PDs are highlighted. This review enlightens the development of III–V semiconductor‐based PDs, and their extended applications for optoelectronic devices in general.

Boron-doped carbon nano dot anchored thin film coating on cobalt vanadium oxide for ultrafast energy storage devices

Lithium-ion capacitors (LICs) with ultrafast rate capabilities are required to increase the applicability of rechargeable energy storage devices. Considering that the power density of an LIC is primarily determined by the anode properties, carbon coating onto the anode material is a promising method of accelerating electron transfer between particles and alleviating structural collapse during repeated charge–discharge cycles. In this study, a new coating configuration featuring a boron-doped carbon nano dot-anchored thin film on cobalt vanadium oxide (BC-CVO) was demonstrated. The coating morphology, wherein the carbon nano dots were connected by a thin carbon film, induced nano-scale surface roughness on CVO, expanding the contact area between the functional groups on the coating layer and electrolyte. The boron-doped carbon lattice structure provided ultrafast electron transfer inside the CVO particles, which allowed reversible electron transfer even under ultrafast charge–discharge cycles. This morphological and chemical combination significantly improved the ultrafast-rate capability of the LIC anodes (429.6 mAh/g at 4000 mA/g and 534.3 mAh/g after 1000 cycles at 2000 mAh/g) compared to that of bare CVO. Furthermore, an LIC full cell fabricated with a BC-CVO anode and an activated carbon cathode showed high energy and power densities.

Low defect density in MoS2 monolayers grown on Au(111) by metal-organic chemical vapor deposition

Monolayers of transition metal dichalcogenides (TMDs) possess high potential for applications in novel electronic and optoelectronic devices and therefore the development of methods for their scalable growth is of high importance. Among different suggested approaches, metal-organic chemical vapor deposition (MOCVD) is the most promising one for technological applications because of its lower growth temperature compared to the most other methods, e.g., conventional chemical vapor or atomic layer deposition (CVD, ALD). Here we demonstrate for the first time the epitaxial growth of MoS2 monolayers on Au(111) by MOCVD at 450 °C. We confirm the high quality of the grown TMD monolayers down to the atomic scale using several complementary methods. These include Raman spectroscopy, non-contact atomic force microscopy (nc-AFM), X-ray photoelectron spectroscopy and scanning tunneling microscopy (STM). The topographic corrugation of the MoS2 monolayer on Au(111), revealed in a moiré structure, was measured as ≈20 pm by nc-AFM. The estimated defect density calculated from STM images of the as-grown MoS2 monolayers is in the order of 1012 vacancies/cm2. The defects are mainly caused by single sulfur vacancies. Our approach is a step forward towards the technologically relevant growth of high-quality, large-area TMD monolayers.

Elastic shear-stiffening composites with locally tunable mechanics for protection and damping

Shear-stiffening gels are flexible materials whose modulus is significantly increased upon rapid impact. They have applications in protective and other devices but are generally limited by difficult processability and poor shape retention. Here we demonstrate a simple and scalable process for making elastic shear-stiffening composites with locally controllable and complex geometries. We construct elastic shear-stiffening composites combining mechanical integrity with shear-stiffening behaviour and elasticity. Shear-stiffening gels were 3D-printed as thin fibres with interstitial spaces filled with polydimethylsiloxane elastomer to hold the gels in place. The composite exhibits strong impact-resistance and shape recovery, which may be due to synergistic energy absorption and dissipation at the composite interface, as well as to the elastomer architecture. Composite mechanics can also be locally modulated by tuning the infill percentages to selectively vary part stiffness and therefore aid motion and wearer comfort. Similarly, a composite hinge exhibits excellent damping, shown in a robotic demonstration.

Magnetic anisotropy of L1[formula omitted] FeNi (001), (010), and (111) ultrathin films: A first-principles study

In previous experiments, L10 FeNi thin films with different surfaces, including (001), (110), and (111), were produced and studied. Each surface defines a different alignment of the crystallographic tetragonal axis with respect to the film’s plane, resulting in different magnetic anisotropies. In this study, we use density functional theory calculations to examine three series of L10 FeNi films with surfaces (001), (010), and (111), and with thicknesses ranging from 0.5 to 3 nm (from 4 to 16 atomic monolayers). Our results show that films (001) have perpendicular magnetic anisotropy, while (010) favor in-plane magnetization, with a clear preference for the tetragonal axis [001]. We proposed calling this type of in-plane anisotropy fixed in-plane. A film with a surface (111) and a thickness of four atomic monolayers has a magnetization easy axis almost perpendicular to the plane of the film. As the thickness of the (111) film increases, the direction of magnetization rotates towards a tetragonal axis [001], positioned at an angle of about 45° to the plane of the film. Furthermore, the most significant changes in spin and orbital magnetic moments occur at a depth of about three near-surface atomic monolayers. Ultrathin L10 FeNi films with varying magnetic anisotropies may find applications in spintronic devices.

Simulation and Analysis of Photonic Bandgapsin 1D Photonic Crystals Using MEEP

This study presents a comprehensive simulation and analysis of photonic band gaps in one-dimensional (1D) photonic crystals using the open-source software MEEP. Photonic crystals, with their periodic structures, exhibit photonic bandgaps that prevent the propagation of specific wavelengths of light, making them crucial for various optical applications. Unlike previous studies that primarily focused on theoretical and experimental methods, this research introduces a novel computational approach that enhances the accuracy and flexibility of modeling these bandgaps. Through detailed simulations, we explore the impact of different structural parameters on the photonic bandgap properties, providing valuable insights into optimizing these crystals for practical use. Our findings demonstrate significant improvements in the design and understanding of 1D photonic crystals, particularly in tailoring bandgaps for specific applications in optical devices. This work contributes to the advancement of photonic crystal technology by offering a robust framework for their analysis and application.

Comprehensive analysis of structural, mechanical, optoelectronic, and thermodynamic properties of Ba2XBiO6 (X = Y, La) double perovskites using density functional theory

The structural, mechanical, optoelectronic, and thermodynamic properties of Ba2XBiO6 (X = Y, La) double perovskites are critically analyzed using density functional theory. The Birch-Murnaghan equation of state confirms their structural stability, supported by tolerance factor analysis. For Ba2YBiO6 and Ba2LaBiO6, negative formation energies are −0.935 eV for Ba2YBiO6 and −0.836 eV for Ba2LaBiO6, confirming thermodynamic stability. Phonon dispersion curves indicate stable lattice vibrations, reducing the likelihood of spontaneous structural changes or phase transitions. Ba2YBiO6 possesses higher elastic constants C 11 = 222 GPa shows stiffness and exhibits brittle mechanical behavior, whereas the Pugh ratio and C 11 = 217 GPa for Ba2LaBiO6 shows ductility. The Poisson ratio classifies Ba2YBiO6 as a non-central force crystal and Ba2LaBiO6 as a central force crystal. Both materials are indirect band gap semiconductors, with band gap values of 0.75 eV for Ba2YBiO6 and 2.05 eV for Ba2LaBiO6. Optical properties suggest applications in UV and visible light-based optoelectronic devices. Thermodynamic properties, such as Debye temperature and heat capacity, support the idea that these materials are suitable for high mechanical applications. These findings provide insights for designing high-performance optoelectronic and mechanical devices.

Effect of sodium dodecyl sulfate on the dielectric and electrical properties of poly (vinylidene fluoride)-zinc ferrite composites

Polymer composites comprising Poly (vinylidene fluoride) (PVDF) as a matrix, Zinc Ferrite (ZnFe2O4: ZFO) as ceramic filler and Sodium Dodecyl Sulfate (SDS) as a surface modifying agent have been synthesized through a simple solvent casting route for application in energy storage devices. The Scanning Electron Microscopic (SEM) study confirmed that the surface modification through Sodium Dodecyl Sulphate improved the dispersion of ZFO particles in the PVDF matrix. The FTIR Spectrophotometer study revealed the existence of expected functional groups in the modified composites The advantage of treatment of SDS on the composite obtained from blending of PVDF with Zinc Ferrite was investigated. The Impedance Analyzer study indicated that the composite with 1.5 wt.% Zinc Ferrite nanoparticles encapsulated by SDS exhibited the highest dielectric constant and reduced loss tangent. In addition, the experimental values of the dielectric constant were compared with some theoretical models. Further, the PE loop study showed higher remanent polarisation in the 1.5 wt.% SDS treated composite indicating that treatment of SDS on Zinc Ferrite (ZFO) can be adopted to fabricate composites for high energy storage applications.

Advances in Aptamer-Based Biosensors for the Detection of Foodborne Mycotoxins.

Foodborne mycotoxins (FBMTs) are toxins produced by food itself or during processing and transportation that pose an enormous threat to public health security. However, traditional instrumental and chemical methods for detecting toxins have shortcomings, such as high operational difficulty, time consumption, and high cost, that limit their large-scale applications. In recent years, aptamer-based biosensors have become a new tool for food safety risk assessment and monitoring due to their high affinity, good specificity, and fast response. In this review, we focus on the progress of single-mode and dual-mode aptasensors in basic research and device applications over recent years. Furthermore, we also point out some problems in the current detection strategies, with the aim of stimulating future toxin detection systems for a transition toward ease of operation and rapid detection.

High-strength conductive hydrogels based on the Hofmeister effect for friction nanogenerators

Hydrogels have received much attention in the field of flexible electronics as materials with flexibility and multifunctionality. The mechanical strength of conventional hydrogels is usually difficult to meet the requirements of practical applications in electronic devices. How to fabricate a high-strength hydrogel should remain a challenge. Here, a strategy to enhance the mechanical properties of conductive hydrogels based on the Hofmeister effect is reported. The mechanical properties of hydrogels were enhanced by increasing the polymer chain density, enhancing the hydrophobicity and increasing the crystallinity, the high-strength and high-toughness polyvinyl alcohol/carbon nanotubes/polyethyleneimine (PVA/MWCNTs/PEI) conductive hydrogel was successfully produced. The ultimate stress of the hydrogel was as high as 3.5–6.3 MPa, the elongation at break was between 500 and 1200 %, and the toughness was up to 23.62 MJ/m3. The conductivity of high-strength, high-toughness hydrogel is 0.05–0.45 S/m. Hydrogel was manufactured into a single-electrode friction nanogenerator (TENG), and it can easily light up to 100 LEDs. Therefore, this high-strength and high-toughness conductive hydrogel has great potential for TENG applications, offering the possibility of extending the working life of TENG in harsh environments.

Novel AIE liquid crystals with high CPL-active bearing multiple dodecyl/cholesterol-decorated R-BINOL-cyanostilbene

The well-structured circularly polarized luminescence (CPL) active liquid crystal materials (R-BINC-Al and R-BINC-Ch) were synthesized through Suzuki coupling of the R-binaphthyl-cyanostilbene unit, followed by modification with dodecyl chains or cholesterol groups. The influence of chiral sources on the liquid crystal behavior, optical properties, and chiroptical response of R-BINC-Al and R-BINC-Ch was thoroughly investigated. Such results revealed that both molecules exhibited typical aggregation-induced emission (AIE) properties and strong solid-state fluorescence. Concretely, the quantum efficiency (ΦF) values of samples with multiple chiral sources increased from 46 % to 51 % by forming liquid crystals in the smectic C and cholesteric phases, the chirality can be transferred to the cyanostilbene unit through ordered self-assembly in the mesophase, resulting in a significant CPL signal across the molecules. Rightfully, the dissymmetry factor (glum) was increased from -7.92 × 10–3 to -1.53 × 10–2 with the introduction of chiral cholesteryl groups. our work elucidated the relationship between multiple chiral sources and CPL behavior, offering a systematic approach to designing chiral luminescent materials in the liquid-crystal phase with high ΦF and substantial glum values, providing a theoretical framework for potential applications in optoelectronic devices.

Tailoring magnetic properties of novel (La0.25Nd0.25Sm0.25Gd0.25)1-xHoxMnO3 high-entropy perovskite ceramics by Ho doping

High-entropy perovskite ceramics (HEPCs) with equal atomic ratios have recently emerged as a highly promising class of materials due to their unique magnetic properties. However, the crystal structure, microstructure and magnetic properties of unequal atomic ratios HEPCs have yet to be fully investigated. In this paper, single-phase HEPCs (La0.25Nd0.25Sm0.25Gd0.25)1-xHoxMnO3 ((LNSG)1-xHxMO) have been synthesized using solid-state reactions. The effect of Ho element content (x = 0.25, 0.3, 0.35 and 0.4) on the structure and magnetic properties was systematically investigated. All samples exhibit an orthorhombic perovskite structure with a Pbnm space group and show obvious crystallization characteristics after sintering at 1250 °C for 16 h (LNSG)1-xHxMO HEPCs display a smooth surface texture and distinct grain boundaries, as well as significant hysteresis effects at T = 5 K. The spin-orbit interaction and magnetic anisotropy between Ho and Mn ions increase with the increase of Ho content, which increases the saturation magnetization (Ms) of HEPCs. (LNSG)0.6H0.4MO exhibits the lowest magnetic hysteresis losses among the considered samples, attributed to its highest Ms (50.95 emu/g) and the lowest coercivity Hc (0.6 kOe). These characteristics endow it with a potential application in magnetic storage devices.

Optimized energy storage with hydrothermally synthesized metal sulfide nanocomposite electrodes

Supercapacitors exhibit impressive energy storage capabilities, providing high power density and quick charge/discharge cycles across various applications, including electronics and renewable energy systems. Molybdenum disulfide (MoS2) plays a crucial role in enhancing supercapacitor performance through its high surface area, conductivity, and electrochemical stability. Recent reports have shown that manipulating phase transitions and incorporating dopants or substitutions can significantly enhance the performance of 2D materials. The present study investigated the influence of tungsten substitution on the phase changes and electrochemical properties of MoS2. The hydrothermal synthesis process involved the substitution of tungsten with different concentration, leading to a notable phase change from 2 H to 1 T, as confirmed by X-ray diffraction (XRD) analysis. Morphological studies using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) revealed modifications in the morphological structure. The electrochemical performance of pristine MoS2 and MoS2/WS2 composites were evaluated using cyclic voltammetry (CV), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS). The determined specific capacitances of MoS2/WS2 composites exhibited higher values compared to pristine MoS2. Specifically, the sample with 15 mol% tungsten addition demonstrated a maximum specific capacitance of 333 F g−1, surpassing that of pristine MoS2 and other samples at a current density of 1 A g−1. This research provides valuable insights into the phase-dependent electrochemical behaviour of MoS2 with tungsten substitution, offering a better understanding of its potential for applications in high-performance energy storage devices.

Micromagnetic study of exchange bias effect in sub-micron dots of Co2MnSi interfaced with uncompensated IrMn

Owing to its crucial role in spintronics devices, the exchange bias (EB) phenomenon has been extensively investigated in various ferromagnet (FM) and antiferromagnet (AFM) bilayers since its discovery in Co/CoO core–shell nanoparticles. In this study, we present the emergence of negative EB for the first time in the Co2MnSi Heusler alloy interfacing with an uncompensated AFM, exhibiting analogous anisotropy to the IrMn. Due to the high pinning and IrMn anisotropy values, EB is stronger here. Investigation into the influence of ferromagnetic layer thickness (tFM) on exchange bias reveals an inverse relationship, while coercivity displays a non-monotonic increase. The analysis of spin canting angles suggests the presence of a maximum canting angle in the Co2MnSi layer close to the interface. We thoroughly analyze the spin configurations at the interface as well as away from it in the Co2MnSi (25 nm)/IrMn (5 nm) bilayer to better understand the mechanism of magnetization reversal. Interestingly, our findings unveiled distinct spin behaviors for the first and second reversals. In cases of small AFM thicknesses (tAFM), the exchange field is proportionate to the tAFM, contrasting with large tAFM, where it scales as 1/tAFM. Notably, coercivity demonstrates an increasing behavior across all tAFM variations. The angular dependence of the Heusler alloy revealed a four-fold symmetry indicative of cubic anisotropy and a two-fold symmetry representative of uniaxial anisotropy. The angular dependency study of exchange bias indicated similar clockwise (CW) and counterclockwise (CCW) rotations, with cos (θ) unidirectional dependence. However, loop shifting revealed that the lower pinning ability at 0° was due to a low Meiklejohn-Bean parameter (R) value. Additionally, through the manipulation of the R-parameter, we can tune the magnitude of the coercive field and EB. All these results are crucial for the utilization of the Co2MnSi/IrMn heterostructures for various applications in spintronics-based devices.

Modeling Study of Si3N4 Waveguides on a Sapphire Platform for Photonic Integration Applications.

Sapphire has various applications in photonics due to its broadband transparency, high-contrast index, and chemical and physical stability. Photonics integration on the sapphire platform has been proposed, along with potentially high-performance lasers made of group III-V materials. In parallel with developing active devices for photonics integration applications, in this work, silicon nitride optical waveguides on a sapphire substrate were analyzed using the commercial software Comsol Multiphysics in a spectral window of 800~2400 nm, covering the operating wavelengths of III-V lasers, which could be monolithically or hybridly integrated on the same substrate. A high confinement factor of ~90% near the single-mode limit was obtained, and a low bending loss of ~0.01 dB was effectively achieved with the bending radius reaching 90 μm, 70 μm, and 40 μm for wavelengths of 2000 nm, 1550 nm, and 850 nm, respectively. Furthermore, the use of a pedestal structure or a SiO2 bottom cladding layer has shown potential to further reduce bending losses. The introduction of a SiO2 bottom cladding layer effectively eliminates the influence of the substrate's larger refractive index, resulting in further improvement in waveguide performance. The platform enables tightly built waveguides and small bending radii with high field confinement and low propagation losses, showcasing silicon nitride waveguides on sapphire as promising passive components for the development of high-performance and cost-effective PICs.

Evaluating the significance of rare earth and iron doping on structure-property of lead titanate

The samples (Pb0.8Ln0.2 Fe0.2 Ti0.8O3, (Ln= La, Nd, Sm, Gd)) were synthesized successfully by mixed oxide method. A significant reduction in tetragonality is observed with the modification of structure. The grain size from FESEM study was observed to be decreasing with increase in ionic radii of rare earth ions. Specifically, the dielectric constant is found to be maximum for the Sm-doped sample. Conductivity studies at varying temperature and frequencies reveal the NTCR behaviour of these samples. In Sm, Nd and Gd doped samples, tunnelling of small polarons is responsible for conduction process whereas for La doped sample, the conduction process is mediated through the combined effect of small polaron tunnelling and bipolaron hopping. The Sm-doped sample exhibits highest remanent polarization. All the results of this comprehensive study provide valuable insights into the effect of dopant ions on various properties of the studied materials, paving the way for device applications.

Design and evaluation of β-Ga2O3 junction barrier schottky diode with p-GaN heterojunction

A novel design for a junction barrier Schottky (JBS) diode based on a p-GaN/n-Ga2O3 heterojunction is proposed, exhibiting superior static characteristics and a higher breakdown capability compared to the traditional Ga2O3 Schottky barrier diode (SBD). By utilizing wide-bandgap p-type GaN, the β-Ga2O3 JBS diodes demonstrate a turn-on voltage (V on ) of approximately 0.8 V. Moreover, a breakdown voltage (V br ) of 880 V and a specific on-resistance (R on,sp ) of 3.96 mΩ·cm2 are achieved, resulting in a Baliga’s figure of merit (BFOM) of approximately 0.2 GW /cm 2. A forward current density of 465 A cm−2 at a forward voltage of 3 V is attained. The simulated reverse leakage current density remains low at 9.0 mA cm−2 at 800 V. Floating field rings, in conjunction with junction termination extension (JTE), were utilized as edge termination methods to attain a high breakdown voltage. The impact of β-Ga2O3 periodic fin width fluctuations on the electrical characteristics of JBS was investigated. Due to the enhanced sidewall depletion effect caused by p-type GaN, the forward current (I F ) and reverse current (I R ) decrease when the β-Ga2O3 periodic fin width decreases. The findings of this study indicate the remarkable promise of p-GaN/n-Ga2O3 JBS diodes for power device applications.

Photothermal-driven soft actuator capable of alternative control based on coupled-plasmonic effect

Recent advancements in small-scale soft actuators have showcased their ability to respond to various stimuli, making them ideal for biomedical engineering and robotics. Light-responsive actuators constructed from photothermal materials such as carbon-based materials have received great attention for their remote wireless control ability. However, conventional carbon-based actuators typically exhibit uniform responses to different light wavelengths, limiting the complexity of their control. To address this limitation, this study develops light-driven soft actuators utilizing gold nanorods (Au NRs) to enhance selective photo-responsiveness. Au NRs are incorporated given their superior ability to convert light energy into localized heat through localized surface plasmon resonances, with efficiency varying based on their size and the wavelength of incident light. By adjusting the specifications of the Au NRs and the wavelength of the optical field, tunable actuation efficiency can be achieved. Experimental calibration confirms that the actuator exhibits differential performance across various wavelengths, enabling more precise control over its behavior. Demonstrations of application devices highlight the actuator’s versatility in flexible robotics, showcasing its potential for advanced applications. This innovation represents a considerable step towards achieving more adaptable and functional soft robotic systems, paving the way for future developments in this area.

Proposal of Damage-Free SiC Wafer Dicing Using Water Jet Guided Laser

A damage-free SiC wafer dicing method has been strongly required for practical applications of power devices. In this research, we propose water jet guided laser processing as a novel dicing method. Water jet guided laser processing, which uses a high-pressure fine water jet as waveguide, could generate no cracks or dislocations in crystal. In this paper, water jet guided laser grooving quality was evaluated to demonstrate there should be no chippings and basal plane dislocations. Scanning electron microscopic and X-ray topography observations were conducted. The results indicated the superiority of water jet guided laser dicing to a conventional dicing method.