Electronic Materials Letters最新文献

Fracture of SiN_x layers within a semiconductor device can cause detrimental reliability issues, and measurement of fracture toughness is key in addressing this limitation. In this study, the fracture toughness of sputtered amorphous SiN_x thin film was quantitatively evaluated using an energy-based nanoindentation method. Analysis of crack morphologies as a function of maximum indentation load revealed a sequential fracture process in 970 nm-thick SiN_x film, consisting of delamination, buckling, and subsequent ring crack formation. The initiation of ring crack formation induced distinct pop-in event in the load–depth curves, which corresponded to an abrupt jump in the irreversible work ((:{W}_{irr})​)–maximum load ((:{P}_{max})​) plot. The energy released during ring crack formation was quantified from the difference in (:{W}_{irr}) with and without ring crack formation at identical maximum load. The calculated fracture toughness was in agreement with expectations with a value of (:6.83:MPasqrt{m}), which is indicative of high reliability of the energy-based method analysis. In contrast, the 94 nm-thick SiN_x film exhibited no significant interfacial delamination under increasing indentation loads. Instead, radial crack propagation through film to substrate and irregular chippings were observed, highlighting the limitations of applying the energy-based method in such thin films. This work demonstrates both the applicability and the thickness-dependent limitations of the energy-based fracture toughness measurement for thin films, providing essential insights for optimizing process parameters to ensure reliability in semiconductor devices with thin coatings.

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This study demonstrates the use of 2,2′,2′′-(1,3,5-benzenetriyl)-tris(1-phenyl-1 H-benzimidazole) (TPBi) as a stabilizing interlayer beneath the Ag top electrode in top-emitting quantum dot light-emitting diodes (QLEDs). The TPBi layer effectively suppresses Ag agglomeration during thermal evaporation, thereby improving film uniformity and optical transmittance from 41.9 to 44.4%. This morphological enhancement yields superior device performance, with the resulting QLEDs based on CdZnSeS/ZnS QDs achieving a peak luminance of 118,110 cd/m² and a current efficiency of 39.3 cd/A. The highest efficiency is obtained at the current density corresponding to peak luminance, which is highly advantageous for practical displays. This work highlights a new functional role of TPBi beyond charge transport and presents an effective strategy to enhance the device performance and fabrication reliability of top-emitting QLEDs for advanced display technologies.

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A comparative study of Cl₂/Ar and Cl₂/O₂ inductively coupled plasma etching of (-201) β-Ga₂O₃ was performed, and the effect of additive gases on the etch characteristics was studied. In both plasma chemistries, as Cl₂ content increased, the etch rate continuously increased and the highest etch rates were obtained at 80% Cl₂ content. In the 40Cl₂/10Ar and 40Cl₂/10O₂ ICP discharges, the etch rate initially increased with increasing ICP source power up to 600 W and then decreased above 600 W, while the etch rate showed a strong dependence on the rf chuck power. The Cl₂/Ar ICP discharges produced significantly higher etch rates than the Cl₂/O₂ plasmas and maximum etch rates of ~ 97 nm/min and ~ 40 nm/min were obtained in the 40Cl₂/10Ar and 40Cl₂/10O₂ ICP discharges, respectively. Under all plasma compositions investigated, the surfaces etched in the Cl₂/Ar plasmas exhibited a constant normalized O/Ga ratio of ~ 0.85, which was somewhat lower than that of the unetched surface. The original stoichiometry was maintained on the Ga₂O₃ surfaces etched in the 40Cl₂/10O₂ ICP discharges while a significant preferential desorption of oxygen atoms was observed for the Ga₂O₃ surfaces etched in the Cl₂/O₂ ICP discharges with Cl₂ content below 60%. Pattern transfer with better anisotropy was achieved with the Cl₂/Ar ICP discharges due to energetic Ar⁺ ion-assisted nature of the etching.

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Lithium iron phosphate (LiFePO₄) has emerged as a promising cathode material for lithium-ion batteries featured by its inherent safety, long cycle life, and low cost. Recently, iron(III) phosphate dihydrate (FePO₄⋅2H₂O) is widely used as the precursor for the synthesis of high-performance LiFePO₄. The physicochemical properties of FePO₄⋅2H₂O critically affect the electrochemical performance of the final LiFePO₄ product. Herein, we systematically investigate the effect of four different iron sources on the material properties of FePO₄⋅2H₂O precursors. A comprehensive characterization was performed to analyze the crystal structure, morphology, hydration behavior and surface properties of the FePO₄⋅2H₂O precursors. Precursors were subsequently converted into LiFePO₄/C composites of which phase purity, carbon coating uniformity, and electrochemical properties were studied. The LiFePO₄/C composite derived from the metallic iron-based precursor demonstrated superior electrochemical performance. The precursor derived from metallic iron can be readily converted to the olivine structure with facile Li⁺ diffusion.

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Due to the depletion and rising cost of lithium resources, sodium-ion batteries (SIBs) have emerged as a promising alternative for large-scale energy storage. However, layered oxide cathodes for SIBs suffer from the structural instability followed by rapid capacity fading. In this study, Ni_0.85Fe_0.10Mn_0.05(OH)₂ precursors, synthesized via co-precipitation, were sodiated at various temperature range from 600 °C to 750 °C to fabricate NaNi_0.85Fe_0.10Mn_0.05O₂ cathodes. The effects of sodiation temperature on structural stability and electrochemical performance were systematically investigated. The cathode sodiated at 700 °C exhibited uniform and spherical secondary particles with an optimal porous structure, leading to the highest initial discharge capacity of 197 mAh g^-1 and excellent rate capability. In contrast, the cathode sodiated at 650 °C delivered superior capacity retention albeit a slightly lower initial capacity, highlighting the importance of a balanced microstructure and crystallinity for the battery performance. Our work underscores that deliberate control of sodiation temperature is required to optimize the phase stability and electrochemical properties of layer-structured cathodes, thereby offering insights for the development of next-generation SIB cathode materials.

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Silicon monoxide (SiO) is a high-capacity alloy-type negative electrode material for lithium-ion batteries, but it suffers from severe volume expansion and low electrical conductivity. Conventional carbon coating by chemical vapor deposition improves conductivity but requires high temperatures (> 700 °C) that trigger disproportionation reactions, leading to the formation of large Si crystallites and accelerated degradation. Here, electroless nickel (Ni) plating is employed as a low-temperature approach to enhance the conductivity of SiO without structural damage. SiO particles were sensitized with SnCl₂, activated with PdCl₂, and coated with Ni via sodium hypophosphite reduction at 50 °C and 80 °C. A higher plating temperature resulted in greater Ni loading and significantly improved cycling stability. These results demonstrate that electroless Ni plating is a thermally benign and effective strategy for advancing the performance of SiO-based negative electrodes.

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Ultrathin ReS₂-based field-effect transistors (FETs) are promising candidates for use in extreme radiation environments, such as nuclear facilities and space missions, due to their layered structure and unique electrical properties. In this study, we investigate the degradation in electrical performance of ReS₂ FETs subjected to 2.2 MeV neutron irradiation. As neutron fluence increases, the on-current and field-effect mobility decrease significantly, from 84% to 31% and from 88% to 37% of their initial values, respectively, while both subthreshold swing (SS) and hysteresis exhibit notable increases. These degradations are attributed to the formation of oxides and the generation of interface traps induced by irradiation. Additionally, threshold voltage shifts are observed, which are attributed to the varying dominance of oxide-trap- and interface-trap-related mechanisms. These findings enhance the understanding of fast neutron irradiation effects on ReS₂-based nanoelectronic devices and support their reliable operation in radiation-rich environments.

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This study explores the use of ultra-thin Mo and Mo₂C films as protective capping layers for graphene-based EUV pellicles, which are essential for next-generation lithography. As semiconductor miniaturization progresses, EUV lithography utilizing materials with high transmittance and mechanical strength, such as graphene, becomes increasingly critical. However, graphene’s vulnerability to hydrogen radicals generated in EUV environments presents a significant challenge. In this research, films less than 5 nm thick of Mo and Mo₂C were deposited on ozone-treated and untreated graphene films using electron-beam evaporation and flip-sputtering methods, respectively. The results reveal that Mo films deposited by e-beam evaporation are prone to etching and cause severe damage to the underlying graphene due to chemical reactions with hydrogen radicals, although Mo films deposited on ozone-treated graphene exhibited higher resistance. Conversely, for amorphous Mo₂C films deposited via sputtering, atomic defects in the graphene increased with prolonged hydrogen exposure, indicating radical penetration through the film. These findings suggest that while Mo offers limited protection, Mo₂C has the potential to serve as an effective capping material for graphene EUV pellicles, provided its resistance to hydrogen radicals can be further enhanced through crystallization. Consequently, strategies to improve the stability and adhesion of Mo₂C are proposed, aiming to develop high-performance, durable pellicle materials for future EUV lithography applications.

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To enhance the battery performance of layer-structured cathode materials, the niobium (Nb) coating was applied using a commercially applicable dry mixing method. The addition of lithium during the coating process induced the in-situ formation of a lithium-niobium-oxide (Li–Nb–O) and uniform distribution on the active material surface, resulting in superior electrochemical performance compared to simple addition of niobium for the dry coating. Furthermore, optimizing the coating temperature facilitated the formation of the Li–Nb–O layer with partial doping of Nb into the bulk structure, thereby simultaneously improving both capacity and cycle-life performance. The electrochemical performance was further enhanced by employing a multi-component coating strategy including aluminum. Moreover, gas generation in pouch-type full cells was evaluated after high-temperature storage in order to assess commercial viability. The Nb-based multi-component coated cathode exhibited less gas generation than its conventional cobalt-coated counterpart, confirming that the Nb-based coating layer effectively suppresses oxygen evolution even at the elevated temperature.

Two-dimensional transition metal dichalcogenides (TMDCs) are promising semiconductors due to their atomic thickness, excellent electrical properties, and tunable bandgaps. While chemical vapor deposition (CVD) enables high-quality TMDC growth, conventional gas-phase methods face limitations in precursor utilization and cost. Here, we demonstrate a scalable solution-based CVD method for monolayer WSe₂ synthesis using an aqueous ammonium metatungstate and sodium cholate precursor. Growth temperature and hydrogen partial pressure were optimized to achieve high-crystallinity films, and large-area uniform monolayers were obtained by controlling precursor film thickness. Fe doping was realized by adding FeSO₄ to the precursor, inducing a carrier polarity shift from ambipolar to n-type. This approach offers a versatile route for scalable synthesis and doping of TMDCs for electronic and optoelectronic applications.

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