Electronic Materials Letters最新文献

Amorphous metal powders, known for their high saturation magnetization, low coercivity (H_c), and reduced eddy current loss, hold great promise for high-performance magnetic devices. However, elevated core losses at higher frequencies—primarily due to eddy currents—impair their efficiency, leading to significant heat dissipation. This study addresses this challenge by investigating the application of low-softening temperature (T_s) glass frits as an insulating coating to enhance the electrical and magnetic properties of Fe_92.3Si_3.5B_3.0C_0.7P_0.5 (wt%) amorphous alloy powders. The practical implications of this research are significant, as it offers a potential solution to the problem of core losses at higher frequencies. The coated powders exhibited superior performance, with the lowest core loss measured at less than 321 mW/cm³ (B_m = 0.2 T at 1 MHz) and a high powder resistivity of up to 1.81 × 10⁹ Ω∙cm while maintaining appropriate permeability. Calculation and experimental results demonstrated that adjusting the coating thickness and ensuring a uniform layer minimized inter-particle and intra-particle eddy current losses. This optimization led to a significant reduction in core loss, enhancing the material’s high-frequency performance. The study emphasizes the critical role of low T_s glass frits in balancing resistivity, magnetic properties, and core loss reduction, offering a practical pathway for developing efficient amorphous alloy powders for advanced magnetic applications, including compact inductors and energy-efficient devices in eco-friendly technologies.

Graphical Abstract

Copper sulfide (CuS_x) is an electrocatalyst which selectively converts CO₂ into HCOOH under harsh conditions. Here, we investigate the formation and kinetics of CuS_x nanostructures on various multi-metal substrates to understand their catalytic properties in sulfur-containing environments. Using a combination of morphological, structural, and electrochemical analyses, we elucidate the time-dependent growth behavior of CuS_x nanostructures with progressive void formation over time. Notably, we discover that CuS_x formation is accelerated on substrates with galvanic corrosion-promoting metals such as Ag and Au, leading to enhanced selectivity for HCOOH during CO₂ reduction. In contrast, coating Cu with corrosion-inhibiting metals like Sn, Ni, or In reduce HCOOH selectivity, highlighting the critical role of galvanic corrosion in the CuS_x formation mechanism and its kinetics. This study experimentally identifies the impact of galvanic corrosion on CuS_x formation mechanisms and offers insights for optimizing electrocatalytic systems.

Graphical Abstract

Herein, we present indium tin oxide (ITO) as a promising candidate for developing adaptable standard resistors. The ITO thin-film device structures exhibit an average resistivity of approx. 1.5 × 10^–4 Ω ⋅ cm, demonstrating remarkable stability in resistance values over time and showcasing temperature-independent magnetoresistance, making them reliable for various applications. ITO resistor structures were found to be optimal with an area ≥10^–7 cm², without observed additional series resistance. The temperature dependence of resistance values changes by approx. 10% within a broad temperature range of 5–310 K in a predictable and repeatable way. Unlike traditional 2D materials, ITO can be processed without the necessity of a protective layer, facilitating easier integration into electronic circuits. Moreover, ITO demonstrates single-type electron characteristics, without hole-like contributions, being particularly suitable as a charge carrier transport control. Our experimental findings indicate that resistors made of ITO-coated glass thin films present a viable alternative to standard chip-type passive components, which are commonly used in electronic devices. This work highlights the potential of ITO as a durable and flexible material for advanced electronics, enabling the design of next-generation resistive elements that can adapt to varying operational conditions.

Graphical Abstract

The emergence of big data and artificial intelligence has promoted the semiconductor industry to increasingly adopt advanced three-dimensional stacking packaging technologies due to the limitations of device scaling. Traditional packaging methods, which rely on micro bumps and adhesives, struggle to meet the growing demands for sub-micrometer fine pitches. To address these challenges, bump-less direct bonding techniques, such as Cu/SiO₂ hybrid bonding, have gained attention, along with surface-activated bonding (SAB) using plasma treatment. However, plasma treatment poses risks, including Cu oxidation and potential short circuits from Cu particle transfer in fine-pitch applications. This study presents a novel plasma-free method that utilizes self-assembled monolayers (SAMs), thin molecular layers that spontaneously create ordered structures on surfaces, for dielectric surface activation. We deposited 3-aminopropyltriethoxysilane (APTES) on silicon dioxide (SiO₂), resulting in a hydrophilic layer that enhances bonding. Notably, a heat treatment significantly improved interfacial adhesion strength through the formation of an amorphous silicon (Si) layer. This SAM-based bonding technique, which enables dielectric surface without the need for plasma, holds promise for future fine-pitch hybrid bonding applications in 3D integrated packaging.

Graphical abstract

This study investigates the light-diffusing capabilities of ZnO nanowires synthesized using the aqueous chemical bath deposition method on PET substrates. By systematically varying Zn source concentrations, the morphology and optical performance of ZnO nanowires were tuned. Scanning electron microscopy revealed that nanowires grown at optimal Zn sources (0.75 g and 1.2 g) exhibited sharp tip morphologies, while higher or lower Zn sources led to flatter tips due to isotropic growth or insufficient precursor availability. Optical characterization demonstrated that ZnO nanowires grown at 1.2 g of the Zn source achieved a maximum total transmittance of ~ 58% and a scattering angle of 53°, outperforming commercial optical diffusers. The transmission haze values peaked at 98.5% for nanowires grown at 1.2 g of the Zn source, attributed to the enhanced refractive index boundaries and optimized structural properties. These findings highlight the potential of ZnO nanowires as high-performance optical diffusers for advanced optoelectronic applications.

Graphical Abstract

Two-dimensional semiconductors such as SnSe₂ hold great promise for electronic and optoelectronic applications. Factors such as the intrinsic carrier concentration and interfacial scattering strongly influence device performance. In this study, SnSe₂-based field-effect transistors were fabricated with precise thickness control by reactive ion etching. Electrical measurements revealed that reducing the thickness from 300 to 21 nm led to an increase in carrier mobility from 3.76 to 26.6 cm² V^− 1 s^− 1 and an improvement in conductivity from 0.31 to 7.72 S/cm. This enhancement is attributed to a rise in carrier concentration, from 1.48 × 10¹⁸ to 1.66 × 10¹⁹ cm⁻³, along with better screening of interfacial Coulomb potential. Furthermore, the photoresponsivity varied with thickness, with thinner devices exhibiting a peak of 484 A/W under a 700-nm laser, compared to 260 A/W under a 900-nm laser for thicker devices. These findings highlight the critical role of thickness optimization in fine-tuning the electrical and optoelectronic properties of SnSe₂-based devices.

Ternary compounds of the Cu–X–Q system (where X = Fe, Sb, Sn and Q = S, Se), such as Cu₅FeS₄, Cu₃SbS₄, and Cu₂SnSe₃, have garnered considerable attention for their potential applications in electronics, optics, and energy technologies. These compounds are noted for their low thermal conductivity and narrow band gaps, making them promising candidates for thermoelectric materials. However, detailed experimental investigations into the phase transitions and thermoelectric properties of synthetic hakite, particularly with Ni substitution, have been limited. This study focused on synthesizing Ni-substituted hakite (Ni_xCu_12−xSb₄Se₁₃; x = 0.5–2) through mechanical alloying and hot pressing techniques, while also exploring the phase transitions and thermoelectric characteristics as a function of Ni content. Despite the charge compensation effect of Ni, a pure hakite phase could not be achieved. Instead, the resultant phases comprised mixtures of secondary phases including bytizite, pribramite, and permingeatite, or their composites. This indicates that the introduction of Ni into the system did not promote the formation of a single-phase hakite but rather stabilized a multi-phase system. The introduction of Ni resulted in a decrease in electrical conductivity across all specimens. Notably, the materials exhibited non-degenerate semiconductor behavior. The measured Seebeck coefficients were significantly high and positive, confirming p-type behavior. However, these coefficients decreased with increasing temperature. The thermal conductivity of the materials displayed minimal temperature dependence, consistently remaining below 0.65 Wm⁻¹ K⁻¹. This low thermal conductivity is advantageous for thermoelectric efficiency, as it minimizes heat loss while maintaining charge transport. For the composition Ni_0.5Cu_11.5Sb₄Se₁₃, we achieved a maximum power factor of 0.09 mWm⁻¹ K⁻² and a peak dimensionless figure of merit (ZT) of 0.18 at 623 K.

Graphical Abstract

This study presents the fabrication and optimization of nanoporous gold (Au) substrates for Surface-Enhanced Raman Spectroscopy (SERS). These substrates were obtained by the high-pressure thermal evaporation method, which utilizes a relatively high pressure of a few Torr to form highly porous structures. These nanoporous structures were induced by homogeneous nucleation and growth of the evaporated metal atoms that occurred through repeated collisions during the deposition process. By controlling deposition pressure and film thickness, optimal conditions to achieve enhanced SERS activity were established. The Au nanoporous structures consisted of randomly connected Au nanoparticles and demonstrated numerous nanogaps between these nanoparticles. These nanogaps act as hot spots of localized surface plasmon resonance, enabling significant amplification of Raman signals. The optimized nanoporous Au substrate, deposited at 2.0 Torr with a thickness of 1.65 μm, achieved a limit of detection (LOD) of 10^− 8 M for Rhodamine 6G (R6G). Furthermore, the substrate’s applicability was extended to the detection of methylene blue (MB), an organic dye with known environmental impacts. MB could be detected up to 10^− 6 M by using these nanoporous Au substrates for SERS. This work successfully demonstrated the potential of nanoporous Au for SERS as an effective analytical platform for trace-level detection of MB, paving the way for advancements in environmental monitoring and biological sensing applications.

Graphical Abstract

Pribramite (CuSbSe₂) is gaining attention as a potential thermoelectric material due to its high thermopower and low thermal conductivity, although it remains relatively underexplored compared to more widely studied thermoelectric compounds. This study focused on optimizing the synthesis and sintering processes of CuSbSe₂ using mechanical alloying (MA) and hot pressing (HP) methods to enhance its thermoelectric performance. The desired pribramite phase was successfully synthesized in both mechanically alloyed powders and hot-pressed specimens, though secondary phases such as bytizite (Cu₃SbSe₃) and permingeatite (Cu₃SbSe₄) were identified. Thermogravimetric and differential scanning calorimetry analyses indicated a melting point for CuSbSe₂ between 723 and 728 K. Densely sintered samples achieved high relative densities of 98.6–99.4% through the MA–HP process. Electrical characterization revealed non-degenerate semiconductor behavior with temperature-dependent conductivity. Seebeck coefficient measurements confirmed p-type semiconductor characteristics, with holes as the major charge carriers. An intrinsic transition in the Seebeck coefficient was observed, with the transition temperature decreasing as the HP temperature increased. A maximum power factor of 0.23 mWm⁻¹ K⁻² was achieved at 623 K, while thermal conductivity steadily decreased across the measured temperature range of 323 K to 623 K. The highest dimensionless figure of merit (ZT) reached 0.28 at 623 K, indicating promising thermoelectric potential for CuSbSe₂.

Graphical Abstract