Yield-stress fluids are ubiquitous and encountered in diverse fields ranging from natural muddy flows to industrial applications such as secondary battery electrode slurries and direct ink writing. Despite the proposal of various constitutive equations, few models have been shown to successfully predict both steady and transient rheological behaviors in yield-stress fluids. In this study, a constitutive equation is hereby proposed, offering a comprehensive description of the rheological characteristics observed in simple yield-stress fluids, excluding thixotropy, such as the Carbopol dispersion. The constitutive equation is derived from a Zener-type viscoelastic solid element combined with an additional linear dashpot connected in parallel, together with a nonlinear viscosity model, a flow rule, an evolution equation for the back stress, and the Kroner-Lee decomposition. This combination satisfies the principle of material frame invariance. The proposed model successfully reproduces the rheological characteristics qualitatively in a manner consistent with experimental observations conducted during startup shear, creep, and stress relaxation tests. In particular, the present viscoelastic solid-based constitutive equation is shown to accurately predict stress overshoot during startup shear. Importantly, the overshoot is found to originate from a homogeneous mechanism in which the normal stress difference enhances the stress invariant, thereby accelerating the plastic response, rather than from isotropic hardening or spatially heterogeneous microstructural evolution. This study is expected to facilitate a deeper understanding of the intricate dynamics governing the flow of yield-stress fluids.

The direct deposition of polymer dielectrics in CMOS fabrication tools is often restricted due to contamination concerns arising from unreacted monomers and process by-products. To enable contamination-free polymer integration, this study employs an external deposition approach in which the organic polymer dielectric pV3D3 is deposited outside the fabrication line and subsequently incorporated into the device structure through a bonding step. This method prevents polymer exposure to process equipment while leveraging the favorable electrical characteristics of pV3D3. The bonded structures were evaluated through electrical and structural analyses. pV3D3 exhibited stable insulating performance in current-voltage (I-V) and capacitance-voltage (C-V) measurements. Scanning acoustic tomography (SAT) and atomic force microscopy (AFM) confirmed void-free bonding interfaces and an atomically smooth surface (similar to 0.3-nm rms) suitable for bonding. Transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS) revealed localized Cu penetration into pV3D3 only after high-voltage stress, indicating that the bonding step itself did not induce material degradation. These results demonstrate that externally deposited pV3D3 can be reliably integrated into semiconductor devices via bonding, providing a practical route toward contamination-free dielectric incorporation in advanced packaging applications.

Biological signals, including neurological signals, are vital for medicine, security, and interface technologies. Their complexity requires high-connectivity and high-performance memory systems, making neuromorphic synaptic devices essential. Inorganic three-terminal devices offer excellent weight linearity and enable back-propagation but lack flexibility due to their rigid structure. Organic counterparts are flexible but suffer from poor reliability and limited bandgap tunability. To overcome these limitations, this study developed a band-engineered charge trap memory (BE-CTM) device using initiated chemical vapor deposition (iCVD), a low-temperature process that enables the formation of uniform hybrid organic-inorganic dielectric layers with a nanometer-scale thickness (≤10 nm) and tunable composition. This hybrid structure combines the mechanical flexibility of organics with the electrical robustness of inorganics, making it ideal for flexible neuromorphic applications. Electrical and reliability tests under biologically relevant voltage pulses confirmed excellent synaptic weight linearity and operational stability under flexible conditions. System-level simulations further demonstrated the device's neuromorphic capability, achieving 93.4% recognition accuracy for handwritten data and 95.8% for noisy images. ECG classification using an MLP model also maintained high accuracy with minimal conductance updates. These results highlight the BE-CTM device's potential for next-generation neuromorphic and biometric information processing.

Industrial plastic waste remains a major environmental concern, particularly in short-lifecycle applications such as prototyping and disposable 3D printing. Although biodegradable polymers offer a promising alternative, their inherently weak mechanical properties hinder widespread adoption. In this study, we present an eco-consciously engineered 3D printing ink composed of cellulose acetate (CA) and muscovite, which forms robust brick-and-mortar microstructures via direct ink writing. The ink exhibits optimized rheological properties and thixotropy, enabling stable extrusion and high structural fidelity during printing. Following printing, CA is converted into cellulose through alkaline treatment, resulting in fully compostable composites. The resulting cellulose-muscovite structures achieve a flexural modulus of up to 6.74 GPa with 20 wt % muscovite, substantially higher than that of polylactic acid (PLA, similar to 2.4-4.9 GPa) and comparable to conventional synthetic plastics. The ink also supports versatile processing, including thin-film fabrication and surface coloration, thereby expanding its potential applications. By combining high mechanical performance, end-of-life compostability, and material circularity, this approach offers a scalable and sustainable solution for reducing plastic waste in temporary or short-lifecycle 3D printed structures.

The CO2 hydrogenation reaction is a promising route for mitigating greenhouse gas emissions by converting CO2 into value-added carbon monoxide through the reverse water–gas shift (RWGS) process. In this study, a surfactant-assisted mechanochemical synthesis was developed to prepare highly dispersed Cu catalysts supported on MgCeOx for the RWGS reaction. The combined use of CTAB (Hexadecyltrimethylammonium bromide, C19H42BrN) and Span®60 (Sorbitan monostearate, C24H46O6) enabled simultaneous control of Cu dispersion, oxygen vacancy concentration, and Ce3 + enrichment under solvent-minimized conditions. The optimized Cu@MgCeOx_CS catalyst achieved 25 % CO2 conversion and complete stability at 440 °C under a gas hourly space velocity (GHSV) of 50,000 h−1 with an H2/CO2 ratio of 4:1. Enhanced redox coupling between Cu+/Cu2 and Ce3+/Ce4+ was verified by precise X-ray analyses, confirming that Cu⁺ species act as the main active sites. This study demonstrates a scalable and energy-efficient route for the synthesis of uniformly mixed Cu–MgO–CeO2 catalysts and provides mechanistic insight into the relationship between surface redox properties and RWGS performance.

The mechanical and interfacial properties of polydimethylsiloxane (PDMS) substrates are strongly governed by their crosslinking density, which is critical for stretchable electronic applications. Herein, we systematically investigate the effect of base-to-curing agent ratio (5:1 to 20:1) on the mechanical behavior, surface wettability, and coating characteristics of PDMS. While a 10:1 ratio is commonly used, we find that a 15:1 ratio provides superior mechanical stability and elastic recovery. In particular, enhanced wettability after plasma treatment further highlights its suitability as a stretchable substrate. Fourier-transform infrared spectroscopy confirms the variation in crosslinking density, while atomic force microscopy phase imaging reveals corresponding changes in surface viscoelasticity. These variations lead to significant modulation of wettability, as demonstrated by contact angle measurements and supported by bonding force analysis, establishing a direct link between surface viscoelasticity and liquid–solid interaction. The impact of these interfacial properties is evaluated using PEDOT:PSS coatings, where coating uniformity, optical transmittance, and sheet resistance strongly depend on the PDMS mixing ratio. Under repeated bending (1000 cycles) and tensile strain, substrates with optimized crosslinking density exhibit enhanced electrical stability. This study establishes a direct correlation between crosslinking density, wettability, and mechanical reliability in PDMS substrates, providing design guidelines for stretchable electronic platforms.

The advancement of interconnect processing technology has been driven by the increasing integration density of semiconductor devices and the high-density memory chips. The subsequent improvement in performance is now determined more by the reduction of RC delay due to interconnects rather than by transistor switching speed. To reduce RC delay, either a low-resistivity metal must be used to lower the interconnect resistance, or an ultra-low-k (ULK) dielectric material with a low dielectric constant must be employed to decrease capacitance. In this study, a device was fabricated using poly-1,3,5-trivinyl-1,3,5-trimethylcyclosiloxane (pV3D3) polymer, which exhibits a low dielectric constant (k = 2.2 ± 0.1). The polymer thin film was deposited via the initiated chemical vapor deposition (iCVD) process, which offers advantages such as solvent-free deposition, minimal monomer damage, high-quality thin films, uniformity, and excellent step coverage. To evaluate the electrical reliability of pV3D3 as an insulating material in a BEOL-relevant metal/dielectric stack, tungsten (W) electrodes were used, and its feasibility as an ILD layer was assessed. Additionally, the interfacial stability of pV3D3 against tungsten was examined, and its superior insulating characteristics were confirmed through electrical measurements. I-V measurements conducted at 25 °C demonstrated a dielectric breakdown field of 5–8 MV/cm, indicating that pV3D3 is suitable for application in interconnect processing and contributes to reducing RC delay. Furthermore, TDDB (CVST) measurements performed under 4.5–5.0 MV/cm conditions provided data for estimating the expected lifetime, offering a foundation for the evaluation of electrical reliability in various polymeric materials. By combining RVST based conduction mechanism analysis with CVST based lifetime modeling, this study provides a systematic reliability assessment of pV3D3 in a BEOL relevant stack. This study is expected to contribute to the development of dielectric materials for reducing RC delay in high-density interconnect processing and to the advancement of reliability analysis techniques for these materials.

Charge-trap nand Flash Memory is a promising nonvolatile storage technology for cryogenic and extreme-temperature electronics. However, its operation and reliability across a wide-temperature range remain insufficiently quantified. In this study, we experimentally characterize nand flash devices from 400 K down to 100K and develop physics-based models to capture the underlying temperature-dependent mechanisms. Wide-range DC measurements reveal an upward shift in threshold voltage (V-th) and an improved subthreshold swing (SS) at low temperatures, accompanied by a reduction in drive current due to mobility degradation in the poly-Si channel. Incremental step pulse programming (ISPP) exhibits weak temperature dependence, consistent with Fowler-Nordheim (FN) injection, whereas incremental step pulse erase (ISPE) shows moderate thermal sensitivity, attributed to thermally assisted detrapping enabled by a reduced effective barrier. Reliability assessments further demonstrate that cryogenic operation enhances both retention and endurance by suppressing thermally activated charge loss and defect generation. The proposed unified modeling framework accurately reproduces the measured V-th evolution and reliability metrics across I - V characteristics, program/erase (P/E) dynamics, retention, and endurance, and enables predictive extrapolation of operating margins and device lifetime for cryogenic computing and other wide-temperature applications.

2D semiconductors are promising channel materials for next-generation thin-film transistors (TFTs) in Internet of Things (IoT) devices. However, their inert, dangling-bond-free surfaces make uniform high-k dielectric integration challenging and can lead to interface defect formation. Here, a scalable inter-dielectric engineering strategy is introduced to address this challenge, using initiated chemical vapor deposition (iCVD) to deposit an ultrathin nonpolar poly(1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane) (pV3D3) film as an interlayer between MoS2 and HfO2. This pV3D3 buffer layer forms uniformly without pinholes or clusters on MoS2, yielding excellent interface quality and effectively suppressing HfO2-induced uncontrollable doping effect and trap formation in MoS2. As a result, the MoS2 top-gate transistors with pV3D3/HfO2 dielectric exhibit nearly ideal switching characteristics, including a subthreshold swing (SS) of 60.9 mV dec-1, negligible hysteresis of ≈20 mV, and low interface trap density (Dit,avg) of 8.9 × 1010 cm-2 e-1 V-1. Furthermore, an overlapping top-gate structure design minimizes contact resistance, achieving an ION/IOFF ratio above 108, a field-effect mobility (µFE) of 19.2 cm2 V-1 s-1, and minimum subthreshold swing (SSmin) of 80.6 mV dec-1. This iCVD based inter-dielectric method is further validated on a flexible MoS2 top-gate transistors and logic circuits, demonstrating its potential for scalable and large-area high-performance 2D electronics.

Particle-laden flow through conduits is ubiquitous in both natural and industrial systems. In such flows, particles often migrate across the main fluid stream, resulting in non-uniform spatial distribution owing to particle–fluid and particle–particle interactions. The most relevant lateral particle migration mechanism by particle–fluid interaction is the Segré–Silberberg effect, which is induced by the inertial forces exerted on a particle, as the flow rate increases. However, methods to suppress it have not been suggested yet. Here, we demonstrate that adding a small amount of polymer to the particle-suspending solvent effectively suppresses the Segré–Silberberg effect in a square channel. To accurately determine the position of the particles within the channel cross-sections, we devised a dual-view imaging system applicable to microfluidic systems. Our analyses show that the Segré–Silberberg effect is effectively suppressed in a square microchannel due to the balance between the inertial and elastic forces at an optimal polymer concentration while maintaining nearly constant shear viscosity.

Yield-stress fluids, widely used in industrial applications such as cement pastes and lithium-ion slurries, primarily consist of dense particulate systems that form networks. Consequently, extensive research has been conducted on their rheological properties and non-Newtonian flow dynamics. Concurrently, lateral particle migration in channel flows has attracted interest because of its impact on the non-homogeneous particle distribution, which affects final product quality. However, lateral migration in a yield-stress fluid with confined geometry remains to be fully elucidated. In this study, the lateral motion and spatial distribution of micrometer-sized beads in microchannels of a carbopol solution were investigated. Owing to their tunable rheological properties and optical transparency, carbopol microgel solutions have been used as model fluids to study particle dynamics. A dual-view imaging system facilitated the identification of two discrete groups in the channel cross section. The first group was located near the channel walls, whereas the second group exhibited a random dispersion pattern in the central region. This contrasts with results reported for macroscale carbopol flows and microscale flows of other non-Newtonian fluids. These discrepancies are attributed to interactions between deformable microgel aggregates and suspended particles, which cannot be accurately predicted using continuum models. This hypothesis was further substantiated using fluorescence experiments that visualized the microscale motion of microgels and suspended particles. These results offer insights into the complex dynamics of particles in microscale flows of macroscopically yield-stress fluids.

The rapid decrease in interconnect Critical Dimensions (CDs) within logic devices and growth in the contact height of 3D memory devices have led to increased contact/via plugs resistance. In this study, we introduce an approach to reduce the resistance of the contact/via plugs by engineering the grain size of the plugs using Nanosecond Green Laser Annealing (NGLA) with a low energy fluence (= 0.1 J/cm2). Because of the proximity between adjacent W plugs, diffraction of the laser light can occur which will help the laser energy to be absorbed by the sidewall of the W plugs. In addition, the difference in reflectivity between the plug region and W interconnect lines can cause grain size enlargement to selectively occur in the plug region. The NGLA process increased grain size in the plugs up to 79.9 %, resulting as much as a 26 % reduction in tungsten plug resistance. The standard deviation of the plug resistance was also improved from 14.6 % to 7.9 % after the NGLA process.

For on‐chip learning, ideal weight storage elements should have scalability, data retention, symmetry and linear conductance modulation, and weight fine‐tuning capabilities. In this study, memristors are fabricated by employing cyano‐based ultrathin copolymer films (<10 nm) using 2‐cyanoethyl acrylate (CEA) and di(ethylene glycol) divinyl ether (DEGDVE) as functional monomers via an initiated chemical vapor deposition (iCVD) process, optimized to serve as a high‐performance device for convolutional neural networks (CNNs). The device achieves highly linear, symmetric, and multi‐level conductance modulation through precise control of polymer composition engineering. The switching characteristics and filament formation are controlled by varying the ratio of CEA and DEGDVE. In addition, the reliability and operation mechanism of the device are studied through non‐invasive observation of the conducting filament dynamics via electrical manipulation using ramp pulse series (RPS). Finally, image classification tasks ares performed on high‐resolution datasets such as Oxford 102 Flowers, Food‐101, and Stanford Cars by varying pulse amplitudes and durations to simulate conductance modulation such as potentiation and depression of weights in memristors. Utilizing various networks such as VGG‐X, ResNet‐X, and DenseNet, the proposed system demonstrated robust performance, achieving up to 88.39% classification accuracy, validating the efficiency of the memristor‐based CNN architecture in real‐world AI applications.

Investigation of silicon as an anode material for lithium-ion batteries (LIBs) is currently underway owing to its high electrical capacity. However, the charging and discharging processes can result in a substantial volume change in the active silicon material, which can eventually lead to pulverization. This phenomenon substantially reduces their lifespan, posing a formidable challenge to their effective utilization, especially for micron-sized silicon particles. To address this issue, research is being conducted to improve the electrochemical properties of silicon anode materials by adding citric acid and borax to the slurry manufacturing process. However, the effect of these materials on the rheological properties of the slurry remains to be fully elucidated. This study systematically investigated the effects of these materials on the shear and extensional rheological properties of micron-sized silicon anode slurries and the electrochemical properties of batteries. This study demonstrated that citric acid and borax significantly affected the microstructure and rheological properties of the silicon anode slurry and the electrochemical performance of the battery. It is expected that this study will facilitate a more comprehensive understanding of micron-sized silicon anode slurry, including its design and optimization.

The rapid reduction of interconnect critical dimension (CD) in logic devices and the increased contact/via height in 3-D memory devices have led to problematic gap-filling processes and the occurrence of void defects, resulting in increased contact/via resistance or complete contact/via failure. However, the low thermal budget of the back-end-of-line (BEOL) stage limits the temperature range available for conventional thermal processes, such as furnace annealing and rapid thermal annealing. This article presents an approach to address contact/via failures, using nanosecond green laser annealing (NGLA) with a low energy fluence (= 0.1 J/cm(2)) . By exploiting NGLA's ability to selectively induce high temperatures for ultrashort durations on metal interconnects, we have developed a process that effectively recovers contact/via failures without compromising the performance of both front-end-of-line (FEOL) and BEOL stages.

Non-Newtonian viscoelastic behavior of disordered spherical micelle dispersions composed of complex coacervate core micelles (C3Ms) in aqueous media is investigated by combining rotational rheometry and microfluidic particle focusing measurements. C3Ms were prepared by mixing oppositely charged block copolymers, resulting in spherical micelles with electrostatically neutral coacervate cores surrounded by hydrophilic coronas. Despite the spherical morphology and dispersion in low-viscosity solvents, lateral migration of micrometer-sized particles in microfluidic flow revealed measurable elasticity. The relaxation time (λ), quantified from particle focusing behavior, increased with micelle concentration and scaled with the short-time Brownian diffusion time scale. This suggests that viscoelasticity in C3M solutions originates from diffusive colloidal dynamics consistent with hard-sphere-like interactions. Upon salt addition, micelle dimension and λ decreased significantly, while solution viscosity remained nearly constant. These results demonstrate that λ can be a quantitative indicator of capturing micellar structural changes under external stimuli. This study highlights the use of centerline particle migration as a sensitive probe for weak viscoelasticity in micellar systems and establishes a quantitative link between micellar structure and relaxation dynamics.

Resistive random-access memory (ReRAM) has attracted considerable attention as a promising memory technology for the internet of things, artificial intelligence, and neuromorphic computing, driving the advancements in the Fourth Industrial Revolution. Among various approaches, ultrathin hybrid films fabricated via an initiated chemical vapor deposition (iCVD) process (iCVD) have emerged as viable candidates for ReRAM devices, offering tunable performance through precise control of the organic-inorganic ratios. However, electrical and chemical properties of hybrid-film-based ReRAM devices have not yet been systemically investigated, making it difficult to establish a comprehensive understanding of conductive filaments (CF) behavior that governs device performance. In this study, we systematically investigate the effects of Al, Hf, and Zr composition variations on the resistive switching behavior of ultrathin hybrid-film based ReRAM (H-ReRAM). Our results demonstrate that the inorganic content of H-ReRAMs gradually reduces the low-resistance state in all H-ReRAM. Conversely, while the high-resistance state (HRS) of Al H-ReRAMs decreases significantly, the HRS of Hf- and Zr-based H-ReRAMs increases, resulting in an improved on/off ratio. Furthermore, we propose a physics-based numerical model that elucidates CF dynamics as a function of the inorganic composition within the hybrid films. This model provides key insights into the material characteristics and switching mechanisms, offering a fundamental understanding that is crucial for optimizing H-ReRAM performance. Our findings contribute to the development of high-performance memory and neuromorphic devices, supporting the next generation of advanced computing systems.

In this study, we propose an approach to relieve the mechanical stress in the gate stack of top-tier devices during the monolithic 3D (M3D) integration process. In the M3D process, selective laser annealing process has been actively adopted for the fabrication of top-tier devices in order to avoid possible adverse effects on pre-existing bottom-tier devices. However, the perpendicular irradiation direction during the laser annealing generates a vertical thermal gradient across the gate stack of top-tier MOS devices, resulting in unavoidable mechanical stress that is detrimental to device performance. In this work, we have demonstrated that inserting an Al2O3 layer in between the TiN gate electrode and the HfO2 gate dielectric can reduce the mechanical stress in the gate stack. This approach can reduce the residual mechanical stress in the gate stack by approximately 67%, resulting in a similar to 49 % reduction in interface state density ( D-it ) and a similar to 20 % improvement in carrier mobility.

As semiconductor devices continue to demand higher performance and density, Cu/polymer hybrid structures have gained significant attention due to their potential to replace conventional SiO2 dielectrics. In this study, we explore the optimization of dry etching processes for 1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane (p V3D3 ) a low-dielectric constant polymer ( k=2.2 ), used in Cu/polymer hybrid structures. By employing initiated chemical vapor deposition (iCVD) high purity, p V(3)D(3 )thin films with a thickness of 200 nm were deposited. Various gas mixtures, including O-2, CF4, and Ar, were used for dry etching to evaluate the optimal etching conditions. Results show that the most anisotropic etching occurred with an O-2/Ar gas mixture, achieving an etching depth of 200 nm and near-vertical sidewalls. Detailed analysis of the etching mechanism was conducted using Gibbs free energy calculations and X-ray photoelectron spectroscopy (XPS). The findings of this study provide valuable insights into the fabrication of high-density, high-performance Cu/polymer hybrid structures for next-generation semiconductor devices.

Processing of electrode slurry, which is highly non-Newtonian fluid, is a critical step in the mass production of lithium-ion batteries (LIBs). While extensional flow plays an important role in the electrode slurry processes such as coating, most previous studies have focused only on the shear rheology, due to the lack of a reliable method to measure the extensional rheological properties of the slurry. Here, it is demonstrated that the extensional rheological properties of the anode slurries can be successfully characterized using the stop-flow-dripping-onto-substrate/capillary break-up rheometry (SF-DoS/CaBER). Using this system, it is observed that the extensional rheology of the anode slurry is significantly affected by the blend ratio of the natural and synthetic graphite, as well as the binder and conductive concentrations. Furthermore, the shear rheology-based model predicts much shorter pinch-off times than those measured experimentally, indicating that the yield-stress of the anode slurry is much larger in extensional flow than in shear flow.