Electronic Materials Letters最新文献

Electromigration (EM) failure in solder joints is a persistent reliability concern, especially in advanced electronic packaging structures. In this study, we conducted an EM experiment on solder joints with asymmetric under-bump-metallization (UBM) thicknesses. Open failure occurred at the solder joint with no current crowding effect but the highest atomic flux of EM, which is related to Sn grain orientation. Our work tries to reveal a counteracting effect of Sn grain orientation on current crowding and the essential reason for the EM failure mechanism of solder joints.

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To achieve high-quality sputtered amorphous silicon (a-Si) thin films with low argon (Ar) working gas atom content and high film density, the effects of (:{P}_{Ar}{D}_{TS}) on Ar gas content and film density is investigated. Here, (:{P}_{Ar}) is Ar working pressure and (:{D}_{TS}) is target-to-substrate. The findings from this work indicate that the Ar gas content in the films primarily arises from highly energetic reflected Ar ions that bombard growing a-Si thin films at low (:{P}_{Ar}{D}_{TS}:) values (< 50 Pa·mm). As (:{P}_{Ar}{D}_{TS}) increases, a monotonic decrease in film density is observed. This results well correlates with the declining average energy of sputtered silicon atoms reaching the substrate. Optimal conditions for fabricating sputtered a-Si thin films with both low Ar content and high film density were identified within the (:{P}_{Ar}{D}_{TS}) range of 30–40 Pa·mm. This research could provide valuable insights for researchers seeking to optimize the balance between low working gas content and high film density in sputtered thin films.

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In recent years, there has been increasing interest in developing solutions to maintain human body temperature in extremely cold environments. Wearable electrically heated fabrics have been extensively researched, however, their complex preparation processes and associated environmental concerns hindered their widespread adoption. To address these challenges, this study focuses on develop a novel materials, which suitable for wearable applications with the low energy consumption and environmentally friendly. In this work, a simple and eco-friendly preparation method was proposed. The viscose-based carbon fabric (VCF) was prepared using viscose fabric as the raw material by means of high-temperature carbonization. The VCF exhibits excellent flexible, good electrical conductivity and remarkable photothermal conversion properties as well. VCF can absorb sunlight for heating and also has electric heating properties. Due to its outstanding flexible and thermal capability, the VCF was applied to heat human body under solar radiation; furthermore, the high electric heating efficiency makes it suitable for a wide range of applications, including indoor heating or de-icing treatment. With its strong potential for wearable applications, viscose-based carbon fabric presents a promising, energy-efficient solution for all-day personal thermal management. This research offers a broad and sustainable approach to developing advanced thermal management fabrics for diverse environmental conditions.

Being the fundamental process of advanced back-end-of-line (BEOL) interconnects, the performance of copper (Cu) electrochemical plating (ECP) affects the resistivity of metal lines and plays a crucial role in RC delay and reliability concerns. A great deal of attention has been focused on reducing the Cu voids, but few reports concentrate on the initial period of ECP, especially when the wafer is immersed in the electrolyte. By optimizing the wafer immersion conditions, I achieved a defect image quantification reduction from a maximum of 88ea to a minimum of 0ea, indicating that a void-free Cu line was realized through a standard plating process, thanks to the reduced surface potential difference during the initial phase. As we develop advanced technology nodes such as below the 7 nm technology node, the higher requirement for the RC delay and reliability performance, this work has good potential applications below the 7 nm technology node, because it provides a promising solution to reduce Cu line voids and can be beneficial to alleviate the RC delay and enhance the reliability in back end of line (BEOL) interconnection.

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High-performance chemresistive gas sensors operating at low or room temperatures are of great potential for practical applications. In this work, the oxygen vacancies-rich BiFeO_3 − x microflowers were synthesized using a facile solvothermal route. The characterized results showed that BiFeO_3 − x was assembled with nanosheets, and displayed a diameter of around 1 μm. The as-fabricated BiFeO_3 − x gas sensor exhibited fine sensing properties towards 0.5-5 ppm NO₂ under ~ 23 ^oC, including a response of 2.92 to 5 ppm NO₂, and it also maintained a response of 1.05 towards 50 ppb NO₂. The gas sensor demonstrated a theoretical limit of detection as low as 273 ppb, rapid response/recovery speed (22/69 s), good selectivity, and repeatability. The improved NO₂ sensing mechanism of enriched oxygen vacancies-BiFeO_3 − x was investigated regarding its micro-nano structure and abundant oxygen species.

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Here, we report on the two-dimensional (2D) (PbI₂)_0.5(BiI₃)_0.5 mixed halide memristor, which exhibits nonlinear conductance that surpasses the properties of the simple combination of PbI₂ and BiI₃ binaries. This 2D system is phase-separated into Bi-rich and Bi-poor nanoscale domains rather than forming a single homogeneous phase. Phase boundaries, predominantly featuring iodine vacancies or stacking faults, induce a novel memristive behavior along the c-axis, driven by ion transport perpendicular to the layered structure, making it promising for resistive switching memory (RRAM) applications. In-situ biasing transmission electron microscopy (TEM) reveals the formation of iodine filaments under sweep bias, with ion migration occurring mainly through phase boundaries in the out-of-plane direction. Direct observation of reversible filament formation in this phase-separated iodide system provides new insights into defect-mediated ion migration, resulting in nonlinear resistive switching, with potential applications in neuromorphic computing. The ability to track heavy anions like iodine in the halide memristor provides valuable insights into the similar correlation mechanisms between ion migration and defects in oxide or sulfide-based memristors. This capability could shed light on how defects influence ion transport in a broader range of materials, enhancing the development of resistive switching devices.

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Metal chalcogenides are widely studied as thermoelectric materials due to their finely tunable electronic transport properties over a wide temperature range. FeSe₂ has recently been considered a promising thermoelectric material with investigations focusing on restraining bipolar behavior through doping. In this study, a series of Cl-doped FeSe₂ compositions, a series of FeSe_2 − xCl_x (x = 0, 0.01, 0.025, and 0.05) compositions, were synthesized to investigate the influence of Cl doping. While the gradually decreasing lattice parameters with doping content x suggests successful doping up to x = 0.05, the hole concentration slightly decreased owing to electrons generated by the Cl doping. Nevertheless, the electrical conductivity and Seebeck coefficient show no systematic change with x owing to very low electron generating efficiency, and no distinctive enhancement of power factor is seen for the doped samples. On the other hand, the lattice thermal conductivity gradually and significantly decreased with x from 9.2 W/mK to 6.3 W/mK for x = 0.05 by 32% at 300 K, which is originated from the effective additional phonon scattering due to the difference in mass (55%) and size (9%) between Se²⁻ and Cl⁻ ions. Consequently, a thermoelectric figure of merit is increased to 0.073 from 0.057 at 600 K for x = 0.05.

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Amorphous indium-gallium-zinc-oxide (a-IGZO) has been attracting great attention as a channel material for dynamic random access memory (DRAM) cell transistors due to its superior characteristics including low leakage current, large area deposition, and back-end-of-line (BEOL) compatibility. It should be clearly taken into account that DRAM will also be used in harsh environments such as military surveillance, aerospace, and nuclear power plants. Especially, these situations can cause inevitable and persistent degradation in long-term operations. When the a-IGZO thin film transistors (TFTs) were irradiated by gamma-ray with total doses of 500 Gy, threshold voltage (V_T) was negatively shifted and hysteresis (delta of V_T between forward and backward sweeps) was increased by creating a positive charge in gate insulator. The extracted density-of-states (DOS) and fitted model were employed to investigate the behavior of oxygen vacancy (V_O) in a-IGZO thin film. Electrical performance degraded by gamma-ray irradiation such as changes in V_T, border trap, tail acceptor-like states (g_TA(E)), and shallow donor-like states (g_SD(E)) were recovered through rapid thermal annealing (RTA) under the O₂ ambient.

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WO₃/WS₂ core/shell nanowires were synthesized using a scalable fabrication method by combining wet chemical etching and chemical vapor deposition (CVD). Initially, WO₃ nanowires were formed through wet chemical etching using a potassium hydroxide (KOH) solution, followed by oxidation at 650 °C. These WO₃ nanowires were then sulfurized at 900 °C to form a WS₂ shell, resulting in WO₃/WS₂ core/shell nanowires with diameters ranging from 90 to 370 nm. The synthesized nanowires were characterized using scanning electron microscopy (SEM), Raman, energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD), and transmission electron microscopy (TEM). The shell is composed of 2D WS₂ layers with uniformly spaced 2D layers as well as the atomically sharp core/shell interface of WO₃/WS₂. Notably, the WO₃/WS₂ heterostructure nanowires exhibited a unique negative photoresponse under visible light (405 nm) illumination. This negative photoresponse highlights the importance of interface engineering in these heterostructures and demonstrates the potential of WO₃/WS₂ core/shell nanowires for applications in photodetectors and other optoelectronic devices.

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Bump is a pivotal technology in 3D IC. However, with the reduction in bump size, there is an urgent need for a high-performance barrier layer material to retard the growth of intermetallic compounds (IMCs) at the interface. The study investigated the diffusion barrier properties and mechanical properties of electrodeposited Ni, Ni–15Fe, Ni–44Fe, Ni–42Fe–16W, and Ni–41Fe–28W. Ni–41Fe–28W demonstrated superior barrier properties, with a thickness of 0.42 μm after aging at 150 °C for 720 h. During the early stages of aging, FeSn₂ were formed at the interface, followed by the later generation of blocky Ni₃Sn₄. With a rise in Fe content, the nucleation of Ni₃Sn₄ was suppressed and the wettability and shear strength of the interface were also enhanced. As for Cu/Ni–Fe–W/Sn, a thin layer of FeSn₂ was also formed, and a whitish Ni–Fe–W–Sn layer was developed at the interface. After aging for 720 h, no significant Ni–Sn IMCs were observed. As W content increased, FeSn₂ converted from layered type to island type. The introduction of W significantly inhibited the diffusion of IMCs nucleation at the interface, endowing Ni–Fe–W with excellent barrier properties. Although W reduced the interface wettability, it enhanced shear strength at lower concentrations, with SAC305/Ni–42Fe–16W achieving the highest strength of 34.8 MPa. While as W content increased, the fracture mode shifted from ductile fracture within the solder to mixed ductile–brittle fracture, leading to decrease in interface reliability. This study provided valuable insights for the design of high-performance barrier layers in advanced packaging.

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