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Research Articles

Regular Paper

Effect of Dye Adsorption Time at Constant Temperature on the Photovoltaic Performance of Dye-Sensitized Solar Cells
Ba Wi Hwang, Hyung Jin Kim, Byungyou Hong
J Electr Electron Mater 2026;39(4):382-386.   Published online July 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.4.7
Dye adsorption is one of the most time-consuming processes in the fabrication of dye-sensitized solar cells (DSSCs), typically requiring approximately 24 h at room temperature. In this study, the effect of adsorption temperature and time on photovoltaic performance of DSSCs was investigated in order to reduce processing time and improve device productivity. Nanoporous TiO2 photoelectrodes were immersed in N719 dye solution at 60°C for 3 h, 10 h, 17 h, and 24 h, and their performance was compared with that of cells sensitized at room temperature for 24 h. Photovoltaic characterization under AM 1.5 illumination showed that DSSCs sensitized at 60°C exhibited improved performance compared to those sensitized at room temperature. The device sensitized at 60°C for 3 h showed comparable or higher conversion efficiency than the reference cell sensitized for 24 h at room temperature. The improvement in device performance is attributed to enhanced dye adsorption kinetics resulting from increased reaction rate between the carboxyl groups of N719 dye molecules and hydroxyl groups on the TiO2 surface. Electrochemical impedance spectroscopy analysis revealed reduced recombination resistance at the TiO2/dye/electrolyte interface for cells sensitized at elevated temperature. UV–Vis absorption analysis confirmed increased dye loading on the TiO2 surface for the 60°C condition. These results demonstrate that elevated temperature dye adsorption significantly reduces processing time while maintaining photovoltaic performance, providing an effective strategy for improving manufacturing efficiency of DSSCs.
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CNN-LSTM-Based Multivariate Anomaly Pattern Detection for Battery Management System
Keon-Sik Hong, Sung-Il Seo
J Electr Electron Mater 2026;39(4):418-425.   Published online July 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.4.12
With the rapid expansion of electric vehicles (EVs) and energy storage systems (ESS), ensuring the operational safety of lithium-ion batteries has become a critical technical challenge. Conventional battery management systems (BMS) primarily rely on threshold-based rule logic, which is limited in detecting coupled anomalies and early-stage degradation patterns. In this study, a deep learning-based framework for multivariate anomaly detection is proposed using BMS sensor data, including voltage, current, temperature, state of charge (SOC), and state of health (SOH). Five representative fault scenarios were defined, including thermal runaway precursors, cell voltage imbalance, SOC inconsistency, internal resistance increase, and communication delay. The proposed CNN-LSTM model was compared with conventional Rule-based methods and machine learning models, including Isolation Forest, Autoencoder, and LSTM. Experimental results show that the proposed model achieved the highest performance, with an F1-score of 0.885, an AUC of 0.94, and a detection delay of 8.1 s. In contrast, the Rule-based method exhibited a significantly higher false negative rate of 42.0%, indicating limitations in detecting complex anomaly patterns. These results demonstrate that the proposed spatiotemporal deep learning approach can significantly improve the accuracy and responsiveness of battery anomaly detection. Furthermore, the proposed method is expected to contribute to enhancing safety, reliability, and predictive diagnostics in next-generation intelligent BMS platforms.
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Early Stage Report: Graduate Research

Magnetically Directed Percolation Networks in Polydopamine-Mediated Carbon Nanotube/Fe3O4 Nanocomposites
Dongyeong Gim, Hyeokju Kwon, Minjeong Ha
J Electr Electron Mater 2026;39(3):288-294.
Published online May 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.3.8
Polymer nanocomposites incorporating inorganic nanofillers have emerged as highly promising electromagnetic interference (EMI) shielding materials, combining mechanical compliance with robust conductive percolation networks. Carbon nanotubes (CNTs) are particularly attractive as conductive fillers because their high aspect ratio facilitates percolation at low loadings. Also, CNTs offer superior mechanical durability under deformation compared to rigid, fracture-prone metal nanowires. For EMI shielding, high electrical conductivity is critical as it enhances both reflection and absorption through efficient charge dissipation and conduction losses. However, achieving highly aligned conductive pathways without degrading the intrinsic electrical properties of CNTs remains a significant challenge. Here, we demonstrate a non-destructive magnetic surface-functionalization and alignment strategy. Using a polydopamine (PDA)-mediated route, pristine multiwalled CNTs are uniformly decorated with Fe3O4 nanoparticles (FMWCNTs). This enables highly effective magnetic field-driven alignment at fields as low as 10 mT, promoting the strategic formation of percolation networks. By optimizing the Fe₃O₄/MWCNT ratio for high saturation magnetization and uniform coverage, the aligned FMWCNTs exhibit significant electrical anisotropy, delivering a 10.7-fold higher electrical conductivity in the parallel configuration compared to the vertical configuration. These findings present a scalable, room-temperature platform for engineering directionally enhanced conductivity in polymer nanocomposites, with broad applicability in advanced EMI shielding, flexible electronics, and advanced packaging technologies.
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Regular Paper

Enhanced Photoluminescence of CsPbBr3 via Improved Optical Transparency of Thermally Treated GaN Nanowires
Kwang Jae Lee, Jungwook Min
J Electr Electron Mater 2026;39(3):272-280.
Published online May 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.3.6
GaN nanowire (NW)-based hybrid structures have attracted attention for optoelectronic applications due to their high surface area and efficient carrier transport. However, the optical transparency of GaN NWs is often limited by unintended residual species accumulated on the surface and in the inter-wire regions, as well as defect-related absorption, leading to reduced light transmission. In this work, we demonstrate that thermal annealing significantly improves the optical transparency of GaN NWs grown on indium tin oxide (ITO)/glass substrates. The transmittance increased from 47.9% to 78.5% at 550 nm after rapid thermal annealing at 800oC for 3 min, while a comparable value (~75.5%) was achieved at 600oC for 5 min. PbBr3 was deposited onto the GaN NWs to form hybrid structures, and temperature-dependent photoluminescence (TDPL) measurements revealed enhanced emission stability with suppressed peak shift and reduced spectral broadening. Arrhenius analysis based on a two-channel model revealed that the activation energy of the dominant non-radiative recombination pathway increased from 62 meV in the as-grown sample to 85 meV after thermal annealing, while its relative contribution remained nearly unchanged. In contrast, the shallow trap-assisted pathway exhibited a similar activation energy of approximately 6 meV in both samples, but its contribution decreased from 0.35 to 0.17 after annealing. As a result, the internal quantum efficiency (IQE) improved from 75.9% to 87.4%. These results show that thermal annealing improves optical transparency by removing residuals and suppresses defect-related recombination, leading to enhanced carrier dynamics and improved optical performance of PbBr3-based hybrid structures.
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Review Paper

Academic Progress Report

Metamaterials-Integrated Triboelectric Nanogenerator Systems
Ahmed Mahfuz Tamim, Youngseo Song, Chang Kyu Jeong
J Electr Electron Mater 2026;39(3):238-246.
Published online May 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.3.2
Metamaterials, as artificially engineered structures with unconventional mechanical and acoustic properties, have recently emerged as a transformative platform for enhancing the capabilities of triboelectric nanogenerator (TENG) systems. Since the invention of TENG devices, extensive efforts have been devoted to improving charge density, output stability, and overall performance. Conventional performance optimization strategies mainly rely on device-level improvements such as surface chemistry modification, microstructuring, and nanopatterning. However, limited emphasis has been given to system-level development of smart self-powered intelligent systems. The integration of metamaterials into TENG devices opens a new era by enabling frequency-selective localization, mechanical impedance matching, and controllable deformation pathways. These engineered mechanical structures not only improve energy harvesting efficiency but also introduce new functionalities into the system. This review systematically summarizes recent advances in metamaterial-integrated TENG systems across four major application domains: (i) energy harvesting, (ii) acoustic telecommunication and acoustic-to-electric conversion, (iii) self-powered sensing, and (iv) vibration suppression and monitoring. Overall, the integration of metamaterials into TENG systems will pave the way for next-generation sustainable, intelligent, self-powered devices with diverse functionalities.
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A Study on the Explosion Characteristics of Off-Gases from Lithium-Ion Battery Thermal Runaway for EVs Marine Transport Safety
Jeong-hoon Park, In-chul Park
J Electr Electron Mater 2026;39(1):52-58.   Published online January 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.1.6
As electric vehicles (EVs) are rapidly adopted worldwide, large numbers are now transported by sea on dedicated car carriers. With this trend, concerns are increasing about fires and explosions caused by battery thermal runaway during marine transport, while existing SOC limits before loading remain largely empirical. This study experimentally investigates gas generation and explosion characteristics of EV lithium-ion cells under thermal runaway conditions representative of enclosed vehicle decks. We identify and quantify the main off-gas components and clarify the flammability behavior and explosion limits of key combustible species. The results provide basic data for assessing EV battery accidents at sea and support the development of safer ventilation and gas-management strategies for ships.
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Quench Behavior of Wires for Superconducting Fault Current Limiters at DC Faults
Hye-rim Kim, Bong-man Ahn, Byoung-sung Han
J Electr Electron Mater 2026;39(1):19-26.   Published online January 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.1.3
The quench behavior of wires for superconducting fault current limiters at DC faults was simulated, with a focus on the effect of capacitor discharge on the quench. The behavior was also expressed in mathematical forms to facilitate a better understanding of the simulation results and for rough analytical estimations of the wire length suitable for the circuit voltage and capacitance. The quench resistance development behavior for various wire lengths and circuit capacitances was simulated using the model developed in the previous work. The quench behavior was expressed in mathematical forms, reflecting the concept of heat balance. During the quench, the wire temperature increased more slowly for longer wires, but was found to increase in a similar pattern. The wire length estimated by the mathematical formula was close to the one obtained by the simulation, with an error range of a few %. The calculations will be used to estimate effectively the length of wires needed to build superconducting fault current limiters for applications in DC power systems.
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Balanced Charge Distribution by the Interface Controls of P3HT: PC70BM/Overlay Active-layers in Organic Photovoltaics
Gyumin Kyung, Hoseung Kang, Soonho Hong, Sunyoung Sohn
J Electr Electron Mater 2026;39(1):94-102.   Published online January 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.1.12
Organic photovoltaics (OPVs) are attractive candidates for sustainable energy conversion due to their flexibility, lowcost processing, and compatibility with large-area fabrication. However, their efficiency is hindered by interfacial defects and vertical phase separation in the active layer, which induce charge imbalance and recombination losses. This work presents an interfacial engineering approach to overcome these limitations in P3HT:PC70BM-based OPVs. Two key strategies were employed: (i) reducing the post-deposition annealing time of the active layer to suppress PC70BM accumulation at the bottom electrode, and (ii) using a DCB:DCM mixed solvent system to regulate solvent evaporation, thereby promoting uniform film formation during PC70BM overlay deposition. Devices fabricated with these optimizations exhibited notable enhancements, achieving short-circuit current density up to 15.83 mA/cm2 and a 58.1% increase in power conversion efficiency compared to control devices. X-ray photoelectron spectroscopy confirmed reduced surface aggregation of PC70BM, while X-ray diffraction indicated improved P3HT crystallinity and molecular ordering. These results highlight the critical role of interfacial and morphological control in enhancing charge separation and transport, offering a practical route toward efficient, reproducible, and stable OPVs.
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A Study on the Development of an Uninterruptible Diagnosis Determination Method for Molded Transformers Using Multiple Diagnosis Sensors
Seok Myung Bae, Yong Moo Chang, Hyo Jin Kim
J Electr Electron Mater 2025;38(5):573-579.   Published online September 1, 2025
DOI: https://doi.org/10.4313/JEEM.2025.38.5.14
With the rapid development of digital technologies such as IoT, AI, and big data, electrical energy consumption is rapidly increasing. Electrical facilities that supply electrical energy are operated with high reliability and stability for end-of-life time. In addition, depending on the type of electrical load that consumes electrical energy in various forms, electrical insulation systems deteriorate due to electrical and thermal stress, which reduces electrical and mechanical insulation strength. Due to such continuous stress and electrical transient phenomena, electrical facilities may experience electrical accidents due to electrical insulation breakdown before the expected design lifetime. In addition, periodic inspections according to related regulations must be conducted to prevent unexpected electrical accidents, but this leads to problems in which the electrical facilities cannot be turned off. Therefore, it is believed that an uninterruptible diagnostic judgment technique that determines compliance with related regulations such as electrical facility technology standards, internal wiring regulations, and inspection regulations without turning off the electrical facilities and at the same time detects abnormal conditions of the facilities early, it is possible to prevent electrical accidents and improve the efficiency of electrical facilities. In this paper, we propose an uninterruptible power diagnosis judgment technique that can prevent or reduce electrical accidents in cast-iron transformers by applying judgment criteria of diagnostic sensors for various types of measurement parameters that can diagnose and evaluate the presence or absence of abnormalities in electrical equipment, including partial discharge, and AI algorithms learned from data of diagnostic sensors.
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Analytical Drain-Induced-Barrier-Lowering Model of Elliptic Gate-All-Around FET with Ferroelectric
Hakkee Jung
J Electr Electron Mater 2025;38(4):396-403.   Published online July 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.4.7
Drain Induced Barrier Lowering (DIBL) was analyzed when the channel of Gate-All-Around (GAA) FET, which is the most promising in the miniaturizing transistor structure, has an elliptic cross-section. The oxide film structure used a stacked Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) structure using SiO2 and ferroelectric. An analytical DIBL model was presented to analyze the DIBL in elliptic GAA FET with ferroelectric. Its validity was proven by comparing the results of other papers. As a result, the Drain Induced Barrier Rising (DIBR) effect, that is, the negative DIBL effect, appeared depending on the ferroelectric thickness tfe, and the ratio of the remanent polarization Pr and coercive field Ec in the ferroelectric, Pr/Ec. The DIBL varied linearly with tfeEc/Pr, and the slope depended on the rate of change for the drain voltage of the ferroelectric charge Q, dQ/dVds. The tfeEc/Pr value satisfying DIBL=0 mV/V decreased as eccentricity increased. The ferroelectric thickness tfe will have to be decreased because the subthreshold swing increases if the Pr/Ec is increased to reduce the tfeEc/Pr value. The threshold voltage increased at this time, but the effect was minimal.
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Dielectric Characteristics of (BaCaSr)(TixZr1-x)O3 Dielectric Ceramic with Temperature Compensation Capacitor Characteristics
Yoo Jung Choi, Hong Sun Lee, Jung Rag Yoon
J Electr Electron Mater 2025;38(4):376-382.   Published online July 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.4.4
This study developed a dielectric composition for high-capacitance MLCCs with C0G and U2J temperature compensation characteristics (Class I) under reducing conditions. The potential application of this composition in highpermittivity class I MLCCs was examined. Using (Ba₀.₂₄Ca₀.₁₆Sr₀.₆)(TiₓZr₁₋ₓ)O₃. XRD analysis showed that secondary phases like Sr₂TiO₄ and TiO₂ formed at higher Ti content, affecting the stoichiometric balance. Adjusting the Ti/Zr molar ratio resulted in a dielectric constant of 41.2 ~ 105, a dielectric loss of 0.082 ~ 0.174%, and insulation resistance above 1.6 × 1013 ohms at 25℃. The TCC shifted from C0G to U2J as the Ti/Zr ratio increased, but the composition enabled the design of high-capacitance and high-voltage MLCCs with favorable dielectric and electrical properties.
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Fabrication and Characterization of Magnetic Field Sensor Based on Fiber Bragg Grating and Terfenol-D Bar
Kwang Taek Kim, Gun Pyo Kim
J Electr Electron Mater 2025;38(3):278-281.   Published online May 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.3.6
We have proposed and demonstrated a fiber optic magnetic field sensor using a FBG (fiber bragg grating) attached on a Terfenol-D bar. The volume of Terfenol-D is changed by the applied magnetic field due to the magnetostriction effect, as a result, the grating period of FBG varies with the intensity of the magnetic field and the Bragg wavelength of FBG is shifted. The temperature sensitivity of the sensor was measured with and without the magnetic field. The temperature sensitivity of the sensor was measured to be 0.02 nm/℃. We observed that the sensitivity of the fabricated device to magnetic field intensity was decreased with the environment temperature.
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Evaluation of Flow Properties of Ceramic Powders Using Static and Dynamic Image Analysis Methods
Ye-won Moon, Hyo-dong Lee, Ji-hui Oh, Jin-ae Kim, Dong-won Lee, Jong-min Oh
J Electr Electron Mater 2025;38(3):254-264.   Published online May 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.3.3
Ceramic powder is an important material used for various purposes in advanced industries, and the fundamental properties of ceramic powder such as particle size, particle size distribution, and flow properties play a decisive role in determining the quality and performance of the final product. In general, these properties have been evaluated through particle size and shape analysis. However, these methods have limitations in providing a comprehensive understanding phenomena related to powder flow, coagulation, and wear. Consequently, performance evaluation based on the analysis of powder flow properties has been increasingly adopted. Previously, flow properties were primarily assessed using funnel-based methods. However, these methods have limitations, as they are challenging to apply to powders smaller than a few micrometers or those with strong coagulation tendencies, and they also suffer from low reliability. To address these issues, this paper introduces a novel piece of equipment that measures flow properties using image analysis and presents various parameters for static and dynamic flow behavior based on this technique. The proposed equipment offers exceptional versatility, as it can be applied to all types of ceramic powders regardless of their size or shape. The principles and measurement methods of the equipment are demonstrated through static and dynamic image analysis of ceramic powders with varying sizes and shapes used as examples.
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A Review on Evaluation of Elastic Modulus Using Nanoindentation
Seo Hyeon Jang, Oh Min Kwon, Si Hyun Park, Hyun Wook Cho, Jong-hyoung Kim
J Electr Electron Mater 2025;38(3):247-253.   Published online May 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.3.2
This review examines the principles, limitations, and recent advancements in elastic modulus measurement using nanoindentation. The importance of accurate contact area prediction is discussed, along with the Oliver-Pharr method and its limitations. The Continuous Stiffness Measurement (CSM) technique is presented as a significant improvement, allowing continuous measurement of mechanical properties throughout the indentation process. For ultra-thin films, the Li and Vlassak method, which incorporates Yu's solution and the concept of effective thickness, is highlighted as a means to correct for substrate effects. Recent developments in artificial neural network-based models for elastic modulus prediction are also explored. These advancements have greatly expanded the applicability of nanoindentation in semiconductor and MEMS device reliability assessment.
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Subthreshold Swing Model of Elliptic Junctionless Gate-All-Around FET Using Ferroelectric
Hakkee Jung
J Electr Electron Mater 2025;38(2):179-186.   Published online March 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.2.8
This paper presented an analytical SS model to determine the subthreshold swing (SS) of an elliptic junctionless Gate- All-Around (GAA) FET using ferroelectric. Analyzing a GAA FET with an elliptic cross-section was essential because it is difficult to manufacture a perfectly circular GAA FET. The results of the proposed SS model agreed well with 2D numerical simulation. Using this analytical SS model, SS was analyzed for the eccentricity and the ratio (Pr/Ec) of permanent polarization Pr and coercive electric field Ec in an elliptic junctionless GAA FET with an MFMIS (Metal-Ferroelectric-Metal-Isulator- Semiconductor) structure using ferroelectric. As a result, the changing rate of the average surface potential due to the gate voltage increased and SS decreased as the eccentricity increased. It was found that the inner gate voltage amplified more than the outer gate voltage due to the ferroelectricity, better controlling the carriers in the channel, thereby reducing SS. As the Pr/Ec decreased, the changing rate of the ferroelectric charge for the outer gate voltage increased and SS decreased. As the eccentricity increased, the changing rate of SS for Pr/Ec decreased. There was no significant change in SS until the eccentricity was about 0.5. The SS began to decline above 0.5 due to the changes in ferroelectric charge, inner gate voltage, and average surface potential for the outer gate voltage.
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AI Algorithm for Stabilizing Output of Multi-Environment Double-Sided Solar Panels
Jongman Kim, Byonghak Moon, Changyong Jung, Sungjin Park
J Electr Electron Mater 2025;38(2):213-218.   Published online March 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.2.13
We propose a real-time information propagation arithmetic neural network (PANN) that minimizes the loss of power generation output of the system in the event of sudden changes in the module due to strong external typhoons or earthquakes at the solar power generation facility site. In addition, we propose a new double-sided module reflector that can reduce the local loss of power generation efficiency of the single-sided module reflector that is currently widely distributed, as well as the environmental pollution and inconvenience of maintenance work of the existing double-sided module. We present a computational network that can detect the faulty solar panel in real-time by checking the fault status of the installed solar panel and using a real-time computation method through a node-to-node diffusion method. In particular, this method recognizes the power loss part due to sudden changes in the module in real time and can take emergency measures for various nonlinear field facilities through a neural structure that finds the optimal distance up, down, left, and right. To confirm the characteristics of the loss reduction control of the field facility, we confirmed that the system was configured as a 7-degree-of-freedom control model using the PANN neural network learning structure method and improved the power generation output. PANN (Propagation Arithmetic Neural Networks) and various module systems are proposed for the real-time recovery of faulty solar panels and improving module system efficiency.
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Influence of Al Content on the Resonant Characteristics of Al-Mo Thin Film-Based SAW Devices
Jae-cheol Park
J Electr Electron Mater 2025;38(1):65-71.   Published online January 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.1.8
Al-Mo thin films were fabricated using combinatorial sputtering system to realize highly sensitive surface acoustic wave (SAW) devices. The Al-Mo sample library was grown with various chemical compositions and electrical resistivities, which provided important information for selecting the most suitable materials for SAW devices. As the SAWs generated from piezoelectric materials are significantly affected by the resistivity and density of the interdigital transducer (IDT) electrodes, three types of Al-Mo thin films with different Al contents were fabricated. The thickness of the Al-Mo thin film used in the SAW-IDT electrode was fixed at 150 nm. As the Al content of the Al-Mo thin film decreased from 81.2 to 30.3 at%, the resistivity decreased slightly from 5.43±0.15 to 4.87±0.1×10-5 Ω-cm, whereas the calculated density increased significantly from 4.1 to 7.9 g/㎤. The SAW device composed of Al-Mo IDT electrodes resonated at 143 MHz without frequency shifts; however, the selectivity of the resonant frequency and insertion loss deteriorated as the Al content decreased. This suggest that the resonant characteristics of the SAW devices fabricated with Al-Mo thin films were more strongly influenced by the material density rather than the electrical properties of the IDT electrodes.
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Optical Properties of SiO2/TiZrO2 Anti-Reflection Deposition Layer on Anti-Glare Surface
Bup Ju Jeon
J Electr Electron Mater 2025;38(1):42-48.   Published online January 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.1.5
This study investigates the effects of chemical etching for anti-glare (AG) treatment and the subsequent deposition of a TiZrO2/SiO2 double-layer anti-reflection (AR) coating on glass surfaces. The AG treatment was performed using ammonium fluoride in gel form via screen printing, followed by electron beam deposition of SiO2/TiZrO2 layers. The surface roughness, optical transmittance, and refractive index were analyzed. The results revealed that while the surface roughness increased with larger screen patterns during the AG treatment, it was reduced by the deposition of the AR layers. Additionally, the gloss caused by external light was higher with lower surface roughness, but it was effectively reduced by the AR coating. The optical reflectance showed minimal changes during the AG treatment, remaining similar to that of bare glass substrates. However, the AR coating significantly decreased reflectance. The combination of AG treatment and AR coating improved optical transmittance and reduced gloss, making this method beneficial for enhancing visibility in automotive displays. The findings suggest that this approach can mitigate the impact of external light and improve the clarity of displayed information, making it suitable for automotive display applications.
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Synthesis of Monodisperse Iron Oxide Nanoparticles with Control of Surface Properties and Magnetization
Dongyeong Gim, Hyeokju Kwon, Minjeong Ha
J Electr Electron Mater 2025;38(1):89-94.   Published online January 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.1.12
Iron oxide nanoparticles (NPs) have gained significant attention for their broad applicability in biomedical imaging, soft robotics, and catalysis owing to their exceptional magnetic properties and biocompatibility. A key challenge in maximizing their functionality lies in achieving a uniform size distribution and dispersity, alongside strong interfacial affinity with the surrounding medium that are essential for optimizing magnetic behavior and processibility. In this study, we present a facile solvothermal synthesis of monodisperse iron oxide NPs with tunable size and controllable surface hydrophobicity by varying precursors, capping agents, and solvents. By varying these synthesis parameters, we demonstrate a clear correlation between NP size, dispersity, and key magnetic properties, including saturation magnetization (MS) and coercivity (HC). This advancement in synthesis methodology offers a reliable, efficient approach for producing high-quality iron oxide NPs, which makes possible for practical use of them across a range of technological and biomedical applications.
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Effect of Packing Density of Alumina Sheet on Sintering Behavior
Hee Hyun Han, Jin Sik Choe, Zee-hoon Park, Hyo-soon Shin, Dong-hun Yeo
J Electr Electron Mater 2024;37(6):609-613.   Published online November 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.6.5
As the operating environment in semiconductor processes becomes demanding, research is being conducted to manufacture dense alumina substrates without defects after sintering to ensure high durability of electrostatic chucks, which are critical components in semiconductor equipment. Therefore, in this study, in order to manufacture green sheets with a high filling ratio for implementing a high-density substrate, alumina powders with average particle sizes of 2.07 μm (L) and 0.37 μm (S) were mixed in ratios of 9:1, 8:2, 7:3, and 6:4, respectively, and green sheets were manufactured and the filling ratio and sintering behavior were observed. Green sheets were fabricated by preparing a slurry using organic materials in Al2O3 powders of different particle sizes. The packing density of the green sheet mixed with L and S alumina powders with different average particle sizes in a ratio of 7:3 before and after binder burn-out showed the highest values of 3.19 g/cm3 and 2.87 g/cm3, respectively. As a result of observing the sintered density based on the mixing ratio of alumina powders revealed that the alumina sheet mixed at a 6:4 ratio of L and S powders, sintered at 1,700℃, exhibited the best sintering characteristics with a density of 3.96 g/cm³.
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Fabrication of YBCO Superconducting Bulk Magnets
Sang Heon Lee
J Electr Electron Mater 2024;37(4):407-411.   Published online July 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.4.7
In this study, we fabricated single grain YBCO bulk superconductors with control of the distance between the seed and the upper surface of the YBCO compacts. The magnetic levitation force of the YBa2Cu3O7 superconducting bulk, which corresponds to the energy amount of the superconducting bulk, was measured to be 32.634 N at the center of the bulk where the seed was placed. Under field cooling conditions, a capture magnetic force of 2.17 kG was observed at the center of the bulk. The trapped magnetic force curve corresponding to the stability of the superconducting bulk means that the superconducting specimens were well grown in the form of single grains.
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Transition Metal-Based Layered Double Hydroxides for Oxygen Evolution Reaction Catalysts
Da-un Han, Gyeongbae Park
J Electr Electron Mater 2024;37(4):358-373.   Published online July 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.4.2
Oxygen evolution reaction is a critical bottleneck for the development of efficient electrochemical hydrogen production because of its sluggish reaction. Among various catalysts, transition metal-based layered double hydroxide has drawn significant attention due to their excellent catalytic properties and cost-effectiveness. This paper begins with basic crystal structures, and then conventional adsorbate evolution mechanism of layered double hydroxide. Strategies for enhancing catalytic properties based on adsorbate evolution mechanism and lattice oxygen mechanism that could surpass theoretical limit of adsorbate evolution mechanism are discussed. This paper ends with a brief discussion on the challenges and future directions of layered double hydroxide-based oxygen evolution reaction catalysts.
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Synthesis and Particle Size Control of δ-FeOOH Using H₂O₂ Oxidizing Agent
Seongmin Shin, Kyunghwan Kim, Jeongsoo Hong
J Electr Electron Mater 2024;37(3):292-296.   Published online May 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.3.8
In this study, Iron (III) oxide-hydroxide (δ-FeOOH) was successfully synthesized using hydrogen peroxide (H₂O₂) as an oxidizing agent. The synthesis of δ-FeOOH was carried out by controlling the amount of H₂O₂, and pure δ-FeOOH was successfully synthesized in ranges from 0.2 mL to 0.6 mL of H₂O₂. The size of the synthesized δ-FeOOH particles was compared by controlling the amount of oxidant H₂O₂. The average particle size of the synthesized pure δ-FeOOH particles increased from 875.1 nm to 897.2 nm as the amount of H₂O₂ was increased. The optical properties of δ-FeOOH synthesized under these specific conditions were investigated. All δ-FeOOH showed a similar trend of increasing and decreasing light absorption from 800 nm to 400 nm, although there was a slight difference in the amount of light absorption, with the largest amount of light absorption at 410 nm. The band gap energy of δ-FeOOH through the Tauc plot method was about 2.1~2.2 eV when H₂O₂ was 0.2~1.4 mL. With a sufficient small particle size, simple control of that particle size, and a small band gap energy enough to absorb light in the visible spectrum, δ-FeOOH could be useful in a variety of applications, including photoelectrochemistry and battery electrodes.
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Optimization of 1.2 kV 4H-SiC MOSFETs with Vertical Variation Doping Structure
Ye-jin Kim, Seung-hyun Park, Tae-hee Lee, Ji-soo Choi, Se-rim Park, Geon-hee Lee, Jong-min Oh, Weon Ho Shin, Sang-mo Koo
J Electr Electron Mater 2024;37(3):332-336.   Published online May 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.3.15
High-energy bandgap material silicon carbide (SiC) is gaining attention as a next-generation power semiconductor material, and in particular, SiC-based MOSFETs are developed as representative power semiconductors to increase the breakdown voltage (BV) of conventional planar structures. However, as the size of SJ (Super Junction) MOSFET devices decreases and the depth of pillars increases, it becomes challenging to uniformly form the doping concentration of pillars. Therefore, a structure with different doping concentrations segmented within the pillar is being researched. Using Silvaco TCAD simulation, a SJ VVD (vertical variation doping profile) MOSFET with three different doping concentrations in the pillar was studied. Simulations were conducted for the width of the pillar and the doping concentration of N-epi, revealing that as the width of the pillar increases, the depletion region widens, leading to an increase in on-specific resistance (Ron,sp) and breakdown voltage (BV). Additionally, as the doping concentration of N-epi increases, the number of carriers increases, and the depletion region narrows, resulting in a decrease in Ron,sp and BV. The optimized SJ VVD MOSFET exhibits a very high figure of merit (BFOM) of 13,400 KW/cm2, indicating excellent performance characteristics and suggesting its potential as a next-generation highperformance power device suitable for practical applications.
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Building Integrated Photovoltaics: Technical and Aesthetic Prospects
Polgampola Chamani Madara, Hasnain Yousuf, Muhammad Aleem Zahid, Suresh Kumar Dhungel, Youngkuk Kim, Junsin Yi
J Electr Electron Mater 2024;37(2):154-163.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.5
The energy demand in the world is expected to exceed 740 million TJ by 2040 and our dependence on fossil fuels needs to be switched to sustainable and renewable energy sources like solar energy. Building Integrated Photovoltaic (BIPV) is one of the best approaches to extracting solar energy. There are more than 200 BIPV products in the market currently but when it comes to integrating these products into the technical aspects such as buildings’ structural integrity, thermal, daylight retainment and aesthetic prospects to be considered. The share of BIPV integration potential of different building types in the world of residential, agricultural, industrial, commercial and other buildings account for 66%, 4.8%, 8.1%, 19.9%, and 1.2% accordingly. Many solar technologies developed to achieve architectural requirements, but the main problem is the trade-off between efficiency and aesthetic appeal, which is less than 10% in coloured and transparent solar modules. This paper discusses the different applications of solar photovoltaics (PV) in building architecture, technical requirements, and different module technologies. The article provides a comprehensive guide for researchers and designers working on the development of BIPV integrations.
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Synthesis of Cu2O Particles Using the Hydrothermal Method
Seongmin Shin, Kyunghwan Kim, Jeongsoo Hong
J Electr Electron Mater 2024;37(1):63-67.   Published online January 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.1.8
In this study, we successfully synthesized copper oxide (Cu2O) particles through a hydrothermal method at a relatively low temperature (150℃). The synthesis involved the precise control of molar concentrations of NaOH. Notably, Cu2O particles were effectively synthesized when NaOH concentrations of 0.15 M and 0.20 M were utilized. While attempts were made at different molar concentrations, the synthesis of pure Cu2O particles was only achieved at concentrations of 0.15 M and 0.20 M. In this experimental investigation, Cu2O synthesized under these specific conditions exhibited absorption characteristics within the wavelength range of 640 to 570 nm, consistently exhibiting a band gap energy of 1.9 eV. These Cu2O particles, characterized by their small band gap energy and straightforward synthetic method, hold significant promise for various applications including semiconductors and solar cells.
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Optimization of Curing Pressure for Automatic Pressure Gelation Molding Process of Ultra High Voltage Insulating Spacers
Chanyong Lee, Hangoo Cho, Jaehyeong Lee
J Electr Electron Mater 2024;37(1):56-62.   Published online January 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.1.7
By introducing curing kinetics and chemo-rheology for the epoxy resin formulation for ultra-high voltage gas insulated switchgear (GIS) Insulating Spacers, a study was conducted to simulate the curing behavior, flow and warpage analysis for optimization of the molding process in automatic pressure gelation. The curing rate equation and chemo-rheology equation were set as fixed values for various factors and other physical property values, and the APG molding process conditions were entered into the Moldflow software to perform optimization numerical simulations of the three-phase insulating spacer. Changes in curing shrinkage according to pack pressure were observed under the optimized process conditions. As a result, it was confirmed that the residence time in the solid state was shortened due to the lowest curing reaction when the curing holding pressure was 3 bar, and the occurrence of deformation due to internal residual stress was minimized.
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Kinematic Design of High-Efficient Rotational Triboelectric Nanogenerator
Jihyun Lee, Seongmin Na, Dukhyun Choi
J Electr Electron Mater 2024;37(1):106-111.   Published online January 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.1.15
A triboelectric nanogenerator is a promising energy harvester operated by the combined mechanism of electrostatic induction and contact electrification. It has attracting attention as eco-friendly and sustainable energy generators by harvesting wasting mechanical energies. However, the power generated in the natural environment is accompanied by low frequencies, so that the output power under such input conditions is normally insufficient amount for a variety of industrial applications. In this study, we introduce a non-contact rotational triboelectric nanogenerator using pedaling and gear systems (called by P-TENG), which has a mechanism that produces high power by using rack gear and pinion gear when a large force by a pedal is given. We design the system can rotate the shaft to which the rotor is connected through the conversion of vertical motion to rotational motion between the rack gear and the pinion gear. Furthermore, the system controls the one directional rotation due to the engagement rotation of the two pinion gears and the one-way needle roller bearing. The TENG with a 2 mm gap between the rotor and the stator produces about the power of 200 __ and turns on 82 LEDs under the condition of 800 rpm. We expect that P-TENG can be used in a variety of applications such as operating portable electronics or sterilizing contaminated water.
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Fabrication of Flexible Micro LED for Beauty/Biomedical Applications
Jae Hee Lee
J Electr Electron Mater 2023;36(6):563-569.   Published online November 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.6.4
Micro light-emitting diodes (LEDs), with a chip size of 100 micrometers or less, have attracted significant attention in flexible displays, augmented reality/virtual reality (AR/VR), and bio-medical applications as next-generation light sources due to their outstanding electrical, optical, and mechanical performance. In the realm of bio-medical devices, it is crucial to transfer tiny micro LED chips onto desired flexible substrates with low precision errors, high speed, and high yield for practical applications on various parts of the human body, including someone’s face and organs. This paper aims to introduce a fabrication process for flexible micro LED devices and propose micro LED transfer techniques for cosmetic and medical applications. Flexible micro LED technology holds promise for treating skin disorders, cancers, and neurological diseases.
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A Brief Review of Research and Development, Market Trends for Ultra-Small and High-Sensitivity Nano Biosensors
Hyeong Gi Park, Jun-won Kook, Kwon-young Choi, Jae-hyun Lee
J Electr Electron Mater 2023;36(6):556-562.   Published online November 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.6.3
This paper presents the development and market trends of nano biosensors. These biosensors must possess high sensitivity and selectivity to effectively detect diseases. Presently, many research groups are focusing on the field-effect transistor aspect of nano biosensors, which can identify diseases such as Down syndrome, bladder cancer, breast cancer, and numerous other cancers, utilizing graphene and transition metal dichalcogenide materials. In the case of in-vitro diagnostics, the use of nano biosensors has been rapidly growing since the onset of the COVID-19 pandemic. This paper also discusses market trends and the outlook for both national and international enterprises engaged in the nano biosensor field. Nano biosensors are expected to play a beneficial and significant role soon, contributing to the early diagnosis of diseases and subsequently improving patient outcomes.
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