Electronic Materials Letters最新文献

This study proposes a novel strategy to enhance the performance of white light-emitting diodes (WLEDs) by integrating graphitic carbon nitride (g-C₃N₄) as an independent blue emitter into Tb³⁺/Eu³⁺-doped lanthanide metal–organic frameworks (Ln-MOFs). Traditional Ln-MOF-based WLEDs suffer from low luminous efficiency due to the Antenna Effect, which compromises energy transfer between ligands and lanthanide ions. By incorporating g-C₃N₄ with high-concentration Tb³⁺/Eu³⁺-doped Ln-MOFs, the optimized composite material, g-C₃N₄@Tb_0.95Eu_0.05-MOF, demonstrated remarkable improvements in photoluminescence properties. Compared to conventional Gd_0.978Tb_0.02Eu_0.002-MOF, the composite achieved a luminous flux of 1.24 lm, luminous efficacy of 1.66 lm/W, and color rendering index (CRI) of 91.6, representing 10.34-fold, 9.23-fold, and 9.0 enhancements, respectively. Mechanistic studies revealed no energy transfer between g-C₃N₄ and Ln³⁺ ions, enabling stable blue emission from g-C₃N₄ while high-concentration Tb³⁺ and Eu³⁺ ions enhanced green and red emissions. This work provides a promising approach for designing high-performance WLEDs.

Graphic Abstract

Alq₃ exists in five crystalline phases, with the δ-phase offering excellent charge transport characteristics owing to its minimal π-orbital overlap and short intermolecular binding distance. Previously, the purification of Alq₃ to obtain this specific phase was achieved using ionic liquids instead of sublimation methods. By controlling concentration and temperature, high-purity δ-phase Alq₃ could be obtained. In this study, the effectiveness of purifying Alq₃ using ionic liquids was examined not through high-performance liquid chromatography measurements but by fabricating and characterizing organic light-emitting devices (OLEDs) to assess improvements in purity and mobility. I–V–L measurements of the fabricated devices revealed a decrease in threshold voltage, an increase in maximum luminance, and a reduction in sub-threshold swing after purification. The I–V characteristics confirmed the effectiveness of ionic-liquid-based purification in enhancing material purity. Lastly, electron-only devices were fabricated, and charge mobility was calculated using the Mott–Gurney equation. The simulation and experimental results were compared to clarify the influence of δ-phase Alq₃ purified with ionic liquids on OLED performance.

Graphical Abstract

The effects of work function and thermal stability of top electrode (TE) materials on the electrical properties of TE/ZrO₂/TiN capacitors for dynamic random-access memory applications were investigated. TEs of Au, Ag, and Al were deposited via thermal evaporation on the atomic-layer-deposited ZrO₂ dielectric layer on a TiN bottom electrode. The high work function of 5.1 eV of Au induced a very stable insulating property, while Ag and Al showed relatively higher leakage current with equivalent dielectric layer fabrication process. To evaluate the interfacial properties between the electrode and dielectric as well as the thermal stability of the electrode, post-metallization annealing (PMA) was performed in an air ambient at 400 °C for 30 min. Ag⁺ ion was diffused into the ZrO₂ layer and Al was oxidized to Al₂O₃ at the interface for Ag and Al TEs, respectively, and severe capacitance degradation occurred. However, Au TE exhibited superior interfacial properties after PMA owing to a curing effect that promoted reducing oxygen vacancies and imperfections near the TE interface, and improved both dielectric and insulating properties.

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The growth and surface functionalization of silicon (Si) thin films have attracted significant attention for applications in microelectronics, photovoltaics, sensors, and actuators. Among various surface functionalities, hydrophobicity is critical in environments where contact with water-based liquids must be minimized. In this study, a 50 μm-thick polycrystalline Si film was deposited on a SiO₂/Si substrate using plasma-enhanced chemical vapor deposition (PECVD). X-ray diffraction revealed a strong (220) preferential orientation with a naturally textured surface morphology. Surface modification with stearic-acid-treated lanthanum hydroxide [SA-La(OH)₃] converted the initially hydrophilic Si surface to a hydrophobic state. When the treatment duration exceeded 12 h, the surface exhibited superhydrophobic behavior, with a water contact angle exceeding 150°. Furthermore, when applied to PET substrates commonly used in flexible electronics and photovoltaic backsheets, the SA-La(OH)₃ coating significantly reduced water vapor permeation by effectively repelling moisture. These results highlight the potential of SA-La(OH)₃ as a robust moisture barrier and a functional coating for hydrophobic surface engineering on Si-based devices.

Layered-perovskite oxide PrBaCo_1.8Fe_0.2O_5+δ (PBCF) was successfully synthesized by sol–gel method. The crystal structure, surface chemical state, conductivity, and electrochemical performance of cathode materials were systematically investigated. X-ray photoelectron spectroscopy analysis revealed that Co ions exist in the mixed valence state of Co²⁺/Co³⁺/Co⁴⁺, while Fe ions in PBCF sample are predominantly in the Fe³⁺/Fe⁴⁺ oxidation state. The PBCF sample exhibits superior electrochemical properties under working conditions, surpassing most previously reported PrBaCo₂O_5+δ cathode materials. Distribution of relaxation times analysis indicates that the charge exchange at the electrode/electrolyte interface becomes the primary rate-limiting step in the oxygen reduction process of PBCF cathode materials.

The development of electrical vehicles (EVs) demands more efficient and environmentally friendly electrode materials to extend the driving range and reduce the cost of the batteries. The transition metal phosphate is considered as a promising solution due to its non-toxicity, affordability and safety. However, its use has been hindered by the low tap density in comparison with layered oxide cathode materials, which limits the volumetric energy density of the batteries. In order to tackle this challenge, we synthesize high-performance LiMn_0.5Fe_0.5PO₄ (LFMP) from carbonate precursors prepared by co-precipitation method. In this work we demonstrated that adjusting key parameters of the co-precipitation process allows formation of dense and spherical precursors for micro-sized LMFP cathode materials. LMFP delivered 137.86 mAhg^− 1 at 50^oC owing to the fast Li⁺-diffusion kinetics. Despite the necessity of further optimization, we believe that our synthesis route could pave the way to the development of high-energy-density batteries based on LMFP.

Graphical Abstract

It is critical to apply wafer-level underfill (WLUF) to establish and improve the stability of microbumps. Although applying WLUF to microbump interconnection layers is common, understanding the behavior of microbump stability without WLUF protection is also critical. Electromigration (EM) and thermal cycling (T/C) tests were performed at a current density of 1.3 × 10⁵ A/cm² at 150℃ and − 45 to 125℃, respectively, to investigate the effect of a WLUF on the reliability for mixed loading of EM and T/C in Cu/Ni/Sn-Ag microbumps. The results of the mixed loading tests showed different failure modes for microbumps with and without the WLUF. Microbump test samples without the WLUF exhibited horizontal cracks. On the other hand, the test samples with WLUF showed cracks propagating obliquely. A series of finite element analyses revealed that the WLUF caused vertical deformation and led to an increase in tensile stress, resulting in oblique crack propagation. These results suggest that the WLUF, due to its relatively high coefficient of thermal expansion, undergoes vertical expansion during thermal cycling, which introduces vertical tensile strain into the microbump structure. As a result, it functions as a stress redistribution layer that modifies the internal stress profile. This redistribution alters the crack propagation path and enhances the mechanical reliability of microbump interconnects under mixed EM and T/C loading.

Graphical Abstract

The insulators in strongly correlated electron systems (SCES) exhibit exotic condensed matter phenomena due to the inherent strong Coulombic repulsion between magnetic cations within their crystal structures, which leads to polaronic hopping conduction, characterized by a high activation energy for carrier transport, and results in unique magnetic properties that vary with environmental conditions. Consequently, the physical properties of SCES insulators can be modulated by tailoring Coulombic repulsion through substitutional doping. In this study, we explore the electromagnetic interference (EMI) functionality of NiWO₄ SCES, which is tuned by substituting magnetic cations (X = V, Co, and Fe) at the Ni site. The magnetic cation-doped NiWO₄ SCES powders were synthesized via solid-state methods and confirmed as single-phase materials through X-ray diffraction (XRD) analysis. To fabricate the EMI film, NiWO₄ powders were mixed with polydimethylsiloxane (PDMS), followed by spin-coating and vacuum oven drying. Although the NiWO₄-PDMS composites were physically mixed, as confirmed by optical measurements such as FT-IR and photoluminescence, the composite exhibited a reflection loss of approximately − 3 dB within the frequency range of 25–40 GHz. Upon substitution of magnetic cations at the Ni site, the X-NiWO₄ samples demonstrated an enhanced reflection loss of -8 dB, attributed to variations in magnetization. These findings highlight the EMI functionality of NiWO₄ SCES and the potential for further enhancement through magnetic cation doping. Given the simple composition of the NiWO₄-PDMS system, SCES materials introduce the potential for advanced EMI functionality, providing insights into different mechanisms that can be achieved through optimized structural and compositional modifications.

The development of low-cost, high-activity non-precious metal catalysts for the oxygen reduction reaction (ORR) is of great significance in promoting the large-scale commercialization of fuel cells (FCs). This study successfully prepared nitrogen-coordinated Cu/Fe bimetallic-doped porous carbon catalysts (Cu/FeNC), which enhance the catalytic activity and stability of the ORR by introducing Cu to optimize the electronic structure of the active site of Fe. Additionally, the influence of Cu/Fe ratio and calcination temperature on the physicochemical properties and performance of the catalysts was investigated. The optimized Cu/FeNC catalysts exhibited a large specific surface area (567.8 m²·g^− 1) and an abundant mesoporous structure. In alkaline media, the Cu/FeNC demonstrated excellent ORR catalytic performance, characterized by a high onset potential of 0.98 V, a half-wave potential of 0.86 V, and a limiting current density of 5.2 mA·cm^− 2. Compared to commercial Pt/C, Cu/FeNC exhibited superior methanol tolerance and better long-term stability, retaining 91.2% of its activity after 6 h. This study provides a novel approach for synthesizing high-performance and low-cost bimetallic catalysts.

Graphical Abstract

This study investigates the effects of Si content on the microstructure, mechanical properties and thermal conductivity of Al-1MM (Misch Metal) alloys. The phase transformation during solidification was analyzed using Pandat software, and the microstructure was examined through SEM and EDS. Fluidity tests were conducted to evaluate castability, while electrical and thermal conductivity were measured for both as-cast and extruded conditions. The results show that increasing Si content in Al-1MM alloys leads to the formation of finer intermetallic compounds and eutectic structures compared to commercial ADC12 alloy. The addition of MM improves electrical and thermal conductivity by forming intermetallic compounds with Si. While tensile strength increases with Si content, elongation decreases. Al-1MM-xSi alloys exhibit significantly higher ductility compared to ADC12 alloy.

Graphical Abstract