Journal of Electronic Materials最新文献

Cu-Co alloy films with different Co contents were prepared as under bump metallization (UBM) via magnetron sputtering by adjusting the current ratio of Cu and Co targets. The interfacial reactions and solder joint reliability between the UBM layer and Sn96.5-Ag3.0-Cu0.5 (SAC305) solder after one, three, and five reflow soldering cycles were investigated. The results indicated that a scallop-like Cu₆Sn₅ phase forms at the SAC/Cu interface, while the introduction of the Cu-Co UBM transforms the interface into a layered structure containing the (Cu,Co)₆Sn₅ phase. Additionally, the intermetallic compound (IMC) layer dissolution phenomenon was observed in the 0.5 A sample after one and three reflow cycles, as well as in the 0.5 A and 1 A samples after five reflow cycles. The IMC thickness exhibits a trend of first decreasing and then slowly increasing with increase in the Co target current, which is the combined result of the Co target current, reflow cycles, and Co content regulating the microstructure, atomic diffusion behavior, and nucleation process of the UBM layer. Shear tests showed that, except for the solder joints with the 0.5 A Co target current after five reflow cycles, where the coarsened (Cu,Co)₆Sn₅ particles act as crack sources leading to reduced joint strength, the shear strength of all the other Cu-Co UBM solder joints was higher than that of SAC/Cu solder joints. In conclusion, a Co target current of 2 A (corresponding to a Co content of 21.88%) is the optimal process parameter for preparing Cu-Co films, at which the IMC thickness is stable and the solder joint shear strength is high.

In this study, zinc tungstate (ZnWO₄), nickel hydroxide (NiH), and their nanocomposites at different ratios (ZnWO₄/NiH = 1:1, 2:1, and 1:2) were synthesized by the hydrothermal method and evaluated as an electrochemical energy storage electrode material. The successful preparation of pristine and composite materials was confirmed by x-ray diffraction, revealing that the ZnWO₄/NiH (1:2) composite possessed the smallest crystallite size of 14.8 nm. The ZnWO₄/NiH (1:2) composite showed ZnWO₄ nanorods present over the NiH nanosheets. Electrochemical analysis by a three-electrode system indicated specific capacity of 671.4 C/g for the ZnWO₄/NiH (1:2) at a current density of 1 A/g. The charge storage behavior indicated that the electrochemical reaction was primarily diffusion-controlled. The designed ZnWO₄/NiH (1:2) prototype device yielded specific capacity of 696 C/g, power density of 9955.6 W/kg, and energy density of 61.9 Wh/kg, with 70% cyclic stability and 98% coulombic efficiency for 5000 galvanostatic charge–discharge (GCD) cycles.

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Silicon carbide (SiC) is a promising third-generation semiconductor material with exceptional properties and significant potential for power semiconductor applications. The continued advancement of SiC MOSFET technology necessitates precise control over the doping concentration in SiC epitaxial layers, particularly for thick films used in high-voltage devices. In this study, we investigate the anomalous drift in doping concentration observed during the growth of 4H-SiC epitaxial layers, which is attributed to variations in the ring coating thickness. Experimental results demonstrate a clear correlation between ring coating thickness and dopant incorporation, with thicker coatings resulting in higher doping levels. To elucidate the underlying mechanism, numerical simulations were performed, revealing that variations in coating thickness modulate the surface distribution of the effective C/Si ratio and influence nitrogen incorporation. This study enhances the understanding of the mechanisms controlling doping concentration in SiC epitaxial growth and provides insights into improving doping uniformity in thick-film epitaxy.

This study systematically investigates the adsorption behavior of sodium atoms on zigzag (7,0) and armchair (7,7) carbon nanotubes (CNTs) using first-principles calculations, focusing on their effects on the electronic structure and optical properties. Three adsorption configurations—inner, outer, and double-sided—were analyzed to clarify the mechanisms of charge transfer and orbital hybridization. The results indicate that internal adsorption in zigzag (7,0) CNTs (−9.43 eV) and external adsorption in armchair (7,7) CNTs (−8.16 eV) achieve a favorable balance between adsorption stability and desorption reversibility, with adsorption energies and diffusion barriers that are more consistent with practical requirements. Optical analyses show typical Drude-type conductive behavior and pronounced polarization in both systems, with the double-sided structure displaying the strongest dielectric and optical conductivity responses. These findings provide valuable theoretical guidance for the design and optimization of carbon-based sodium-ion battery electrodes.

Porous carbon materials have long been a research focus in supercapacitor electrode materials owing to their excellent electrical conductivity, high specific surface area, and good chemical stability. Herein, we propose an approach for the preparation of porous carbon materials using the ice crystal template method combined with carbonization and activation of chitosan and dopamine hydrochloride polymer networks as precursors. The effects of the ratio of precursors to KOH activator on the electrochemical performance of the materials are systematically studied. The results show that the optimized sample exhibited a high specific capacitance of 317.8 F g⁻¹. Furthermore, the device assembled with this material as the negative electrode and self-made Ni(OH)₂ as the positive electrode delivered energy density of 18.7 Wh kg⁻¹ with capacitance retention of 96% after 10,000 cycles.

This work introduces an alternating deposition approach for nanographene-MoS₂ composite thin films using pulsed laser deposition (PLD) to enhance charge separation and photoresponse efficiency. Nanographene films and nanographene-MoS₂ composite thin films were successfully fabricated using PLD via the alternating ablation method. Three samples were prepared: a nanographene film and two nanographene-MoS₂ composite films, GM1 with a 2:1 ratio and GM2 with a 1:1 ratio. These ratios correspond to the relative number of laser pulses applied to each target, while the total number of pulses was fixed at 650 for all depositions. Structural, chemical, and morphological analyses were performed using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and energy-dispersive x-ray spectroscopy (EDS). MoS₂ incorporation improved film uniformity, surface roughness, and structural order, while Raman analysis showed a decrease in the I_2D/I_G intensity ratio, indicating enhanced layer stacking and crystal quality. Photoluminescence (PL) measurements validated the optical bandgap, which diminished as the MoS₂ content increased, indicating enhanced light absorption and reduced recombination. Hall effect measurements showed that the composite films had fewer carriers and higher mobility. Furthermore, films were successfully deposited on soda-lime glass substrates. This is a low-cost, ecofriendly, and low-temperature method for photonic and optoelectronic applications. These results highlight the advantages of alternating PLD-grown nanographene-MoS₂ composite for high-performance photodetectors and offer recommendations for optimizing material composition and deposition parameters for future electronic and optoelectronic devices.

As electronic devices scale down to atomic-level quasi-two-dimensional (2D) nanosheets, molybdenum disulfide (MoS₂) has emerged as a promising channel material due to its superior electronic and mechanical properties. However, the integration of MoS₂ into next-generation transistors faces critical challenges, primarily due to phonon scattering, which degrades current flow and limits device performance, particularly as channel lengths become shorter and operating temperatures rise. To address this issue, this study investigates the combined effects of strain engineering and high-k dielectric materials on MoS₂ field-effect transistors (FETs). Utilizing a modified ballistic FETToy model with a top-of-the-barrier (ToB) model approach, phonon scattering was incorporated via transmission probability, which is dependent on both channel length and temperature. Strain effects were modeled by adjusting the electron effective mass. The results indicate that phonon scattering reduces the current by up to 43.5% at a channel length of 10 nm compared to ballistic operation, with increased impact at elevated temperatures. Compressive strain mitigates these effects, increasing the current by 13.1% at 10 nm, while tensile strain further suppresses performance. High-k dielectrics also substantially improve current flow and, when used in conjunction with compressive strain, yield a 22.4% enhancement in current relative to the unstrained ballistic reference. These results demonstrate the effectiveness of integrating strain and dielectric optimization within a quasi-ballistic modeling framework, providing a systematic approach for assessing ultra-scaled MoS₂ FET performance.

Accurately calculating magnetic loss under direct current (DC) bias conditions remains challenging, particularly when relying solely on manufacturer-provided data. To overcome the limitations of existing prediction models, which depend heavily on experimental measurements under DC bias, this study proposes a calculation method for magnetic loss in electrical steel based on the elliptic loss model. First, a correction coefficient for magnetic field strength is introduced into the classical elliptic loss model to develop a static hysteresis loss prediction model that incorporates the influence of field strength. Second, the static hysteresis loop under DC bias is divided into upper and lower half-branches, and corresponding static hysteresis loss models are established for each branch. This approach enables the formulation of a static hysteresis loss prediction method under DC bias. Finally, by applying statistical loss theory, a comprehensive magnetic loss prediction model is constructed that accounts for both magnetization frequency and DC bias effects on eddy current and excess losses. The accuracy and applicability of the proposed model are validated by comparing experimental measurements with simulation results.

The transition to low-cost and efficient counter electrodes (CEs) is essential for the widespread deployment of dye-sensitized solar cells (DSSCs). In this study, we report copper–polypyrrole (Cu–PPy) nanocomposites synthesized via chemical reduction, which function as a noble-metal-free CE with excellent electrocatalytic behavior. The enhancement in performance is driven by π–d orbital interactions between the polypyrrole’s π-conjugated structure and the d-electrons of copper, promoting orbital hybridization that facilitates efficient electron delocalization and charge transfer at the electrode–electrolyte interface. X-ray diffraction confirms the presence of a crystalline face-centered cubic (FCC) copper phase embedded within the polymer matrix, while scanning electron microscopy reveals a porous architecture that is conducive to electrolyte infiltration. Electrochemical analyses, including chronoamperometry, cyclic voltammetry, and electrochemical impedance spectroscopy, indicate a notable decrease in charge transfer resistance (1.6 Ω) and a substantial increase in cathodic current density (8.38 mA cm⁻²), reflecting improved redox kinetics. The x-ray photoelectron spectroscopy (XPS) results confirm the successful integration of copper with polypyrrole, showing distinct Cu²⁺ species and nitrogen bonding environments that support interfacial electronic coupling consistent with π–d orbital interaction. When incorporated into a DSSC using methyl orange as the sensitizing dye, the Cu_0.2PPy CE delivered power conversion efficiency of 4.84%, rivaling traditional platinum-based electrodes. This excellent performance arises from the combined effects of orbital-level electronic synergy and nanoscale porosity, which collectively enhance interfacial charge mobility and catalytic accessibility. This work illustrates how rational design of hybrid materials at the molecular orbital level can yield high-performance, scalable alternatives to precious metals in solar energy devices.

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Reduced graphene oxide (rGO) is widely recognized for its superior electrical conductivity, extensive surface area, and adaptability. It has high energy storage capability and a wide range of applications. Its utility in crafting lightweight hybrid electrodes for pseudocapacitors is especially significant, facilitating enhanced charge storage and power output. However, the reduction in accessible area, lower specific capacitance, and power density are major difficulties, which can be overcome by integrating a constant percentage of carbon nanotubes (CNT) and varying concentrations of manganese dioxide (MnO₂) via a vacuum filtration route. This study reports the production and analysis of five different compositions: pure rGO, rGO with 8% CNTs, and rGO with 8% CNTs along with 10%, 20%, and 30% MnO₂. CNTs acted as effective conductive spacers, and MnO₂ served as a redox-active material. The fabricated electrode compositions underwent characterization of various parameters including sheet resistance, conductivity, Brunauer–Emmett–Teller (BET) surface area, specific capacitance, power density, and equivalent series resistance (ESR). The results showed that the rGO-based pseudocapacitive material embedded with 8% CNTs and 20% MnO₂ yielded distinct functional properties including lower sheet resistance of 70 Ω/sq, higher current density of 1.41 S/cm, and improved BET surface area of 310 m²/g, with specific capacitance of 318 F/g, power density of 943 W/kg, and moderate ESR of 1.9 Ω. The results showed significant enhancements in electrical and electrochemical performance, thereby positioning rGO/CNT/MnO₂ hybrids as a promising candidate for advanced lightweight electrode applications.