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Study on OCP Optimization and EIS-Based SOH Estimation for LiFePO4 Battery Packs Under Motor Load Conditions
Woo-Geun Jung, Jae-Ha Ko, Keon-Sik Hong
J Electr Electron Mater 2026;39(4):407-417.   Published online July 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.4.11
This study proposes an optimization strategy for the over-current protection (OCP) parameters of a lithium iron phosphate (LiFePO₄, LFP) battery system used in electric golf carts operating under high motor-load conditions. Real-world hillclimbing tests were conducted under four clearly defined payload/passenger conditions to analyze the transient discharge-current pro-file, voltage sag, and cell-temperature response. The maximum discharge current reached -238.2 A under the 200 kg cargopayload and one-passenger condition, and the current interval exceeding 150 A lasted up to 27 s. The maximum instantaneous power was 11.05 kW. Thermal analysis showed that the cell-temperature rise was within 2°C and the maximum measured cell temperature was 22.3°C. Linear regression of voltage and current yielded R² = 0.9368 and dV/dI = 0.0126 Ω, which was used as the DC internalresistance estimate. Based on these quantitative results and the cell specification limit of 300 A continuous discharge, the OCP threshold was reviewed from 250 A to 280 A to improve driving continuity while remaining below the allowable continuous-discharge current. EIS-based SOH estimation and the AI-BMS variable protection logic are presented as an extension framework for reflecting temperature and aging effects in future OCP-setting decisions.
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Electrical Properties Based on Dielectric Layer Thickness for the Optimal Design of BaTiO3-Based X8R MLCCs
Change-ho Lee, Jong Kyu Lee, Jung Rag Yoon
J Electr Electron Mater 2026;39(2):175-182.
Published online March 1, 2026
DOI: https://doi.org/10.4313/JEEM.2026.39.2.6
This study investigates the effect of dielectric layer thickness on the electrical and reliability characteristics of BaTiO₃- based X8R multilayer ceramic capacitors (MLCCs) for automotive applications. MLCCs with 30 dielectric layers and thicknesses ranging from 5 to 30 μm were fabricated, and key parameters―including capacitance, equivalent series resistance (ESR), insulation resistance (IR), breakdown voltage (BDV), DC-bias characteristics, temperature coefficient of capacitance (TCC), and ripple current-induced heating―were evaluated. The dielectric constant (~2,000) and sintering shrinkage (~-25%) were nearly independent of thickness, confirming stable microstructure formation. ESR increased with thickness, while normalized BDV (V/μm) decreased due to defect accumulation. IR improved with increasing thickness but dropped sharply above 125℃. Dielectrics thinner than 10 μm exhibited significant capacitance degradation under DC-bias and temperature variation, reflecting strong internal field effects. Ripple-induced heating correlated directly with ESR. These results indicate that, although thinner layers enhance capacitance density, reducing the thickness below 10 μm compromises bias stability and thermal reliability. A minimum dielectric thickness of 10 μm is therefore recommended to achieve an optimal balance between electrical performance and durability in high-reliability X8R MLCCs.
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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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Electrical Properties Based on the Number of Stacked Layers for the Optimal Design of BaTiO-Based MLCCs for MIL-PRF-32535 Compliance
Change-ho Lee, Hong Sun Lee, Seok No Seo, Jung Rag Yoon
J Electr Electron Mater 2025;38(5):513-520.   Published online September 1, 2025
DOI: https://doi.org/10.4313/JEEM.2025.38.5.6
Multilayer ceramic capacitors (MLCCs) are essential for high-capacitance, miniaturized, and reliable electronic applications. This study examines the impact of layer stacking on the dielectric and electrical properties of MLCCs using a BaTiO₃-based dielectric with MgO, Mn₃O₄, Yb₂O₃, V₂O5, and (BaCa)SiO₃ glass additives. MLCCs with 10 um-thick dielectric layers and varying Ni electrode layers (10, 30, 50, and 100 layers) were fabricated. The dielectric constant increases significantly up to 30 layers due to compressive stress and sintering densification but it becomes linear beyond 30 layers. Dissipation factor and ESR decrease with higher stacking due to improved sinterability, while breakdown voltage declines exponentially from defect accumulation and thermal stress. Insulation resistance decreases but stabilizes relative to capacitance. C-V results show stress-induced polarization suppression, which reduces the dielectric constant under high voltage. Optimized stacking and sintering conditions are crucial for MIL-PRF-32535 compliant MLCC designs.
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Dielectric Properties of High-capacity BME MLCCs via (Na₀.₅Bi₀.₅)TiO₃ as a Rare-Earth-Free Dopant
Change-ho Lee, Jung Rag Yoon
J Electr Electron Mater 2025;38(5):546-553.   Published online September 1, 2025
DOI: https://doi.org/10.4313/JEEM.2025.38.5.10
In this study, the dielectric and electrical properties of high-capacitance base metal electrode (BME) multilayer ceramic capacitors (MLCCs) fabricated using a BaTiO₃-MgO-Mn₃O₄-(Na₀.₅Bi₀.₅)TiO₃ (NBT)-(BaCa)SiO₃ dielectric system were investigated under reducing atmospheres with oxygen partial pressures (PO₂) ranging from 10⁻1⁰ to 10⁻12 MPa. By incorporating NBT, the dielectric performance remained stable across the entire range of reducing atmospheres. The fabricated MLCCs exhibited consistent capacitance values, low dielectric loss (<2.8%), and high insulation resistance, reaching up to 2.4 GΩ at 25℃ and 0.675 GΩ at 125℃. Furthermore, excellent breakdown voltage performance (up to 550 V at 25℃) and Class II-compatible temperature coefficient of capacitance (TCC) behavior were observed, meeting the X8R specification. The BaTiO₃-MgO-Mn₃O₄-NBT-(BaCa)SiO₃ dielectric system demonstrates that NBT can serve as a promising alternative to conventional rare-earth dopants in BME MLCCs, enabling excellent thermal and electrical stability, high capacitance, and longterm reliability even under reducing conditions. These results confirm the feasibility of developing cost-effective, sustainable, and rare-earth-free MLCCs for high-performance applications in automotive, industrial, and energy storage systems.
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This study examined the crystallinity and potential of BaTiO₃ powder, prepared by hydrothermal synthesis at 60 nm, as a dielectric material for automotive MLCCs under varying heat treatment temperatures. At temperatures above 850℃, the powder exhibited an orthorhombic structure, with crystallinity and particle size increasing as the temperature rose. In the range of 850~900℃, the powder displayed a uniform particle size distribution and minimal agglomeration, with particles ranging between 150~200 nm. Additionally, it was confirmed that the heat treatment temperature significantly impacts the properties of BaTiO₃ powder, which are critical for the dielectric performance required in X7R MLCCs used in automotive applications. Specifically, high-temperature treatment (above 850℃) was essential for enhancing the powder's crystallinity and forming a stable core-shell structure, which is crucial for achieving stable TCC (Temperature Coefficient of Capacitance) characteristics. It was confirmed that increased crystallinity at temperatures above 850℃ facilitated the development of the core-shell structure through interactions with additives, thereby achieving the necessary characteristics required for highly reliable automotive MLCCs.
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The Research Trends of Dielectric Materials for MLCC Applications
Intae Seo, Ho-yeon Kim, Hyoung-won Kang, Cheol-min Oh, Seung-ho Han, Hyungsuk Kim
J Electr Electron Mater 2025;38(2):132-142.   Published online March 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.2.2
This review addresses the development trends of dielectric ceramics, the key material for Multilayer Ceramic Capacitors (MLCCs), which are essential components in high-performance electronic devices. Traditional MLCCs have employed BaTiO3 (BT)-based dielectrics to achieve high dielectric constant and low resistance. By minimizing oxygen vacancies and suppressing grain growth in BT materials, the temperature and voltage stability of MLCCs have been improved, leading to the development of MLCCs with diverse properties. However, the maximum dielectric constant of approximately 3000 in BT materials poses a limitation in overcoming the trade-off between rated voltage and capacitance density. Therefore, ultra-high permittivity dielectric materials have gained attention to meet the requirements of ultra-high-performance MLCCs, and ongoing research focuses on enhancing the temperature and frequency stability of these materials. This review analyzes the characteristics and limitations of conventional BT materials and explores recent research trends and future potential in developing new MLCCs based on ultra-high dielectric constant materials.
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Low-Power LC-VCO Design Based on Si-NWFET Using Switched Capacitor Array
Seung Hyeok Choi, Han Jung Song
J Electr Electron Mater 2025;38(2):200-206.   Published online March 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.2.11
This paper presents a Si-NWFET-based LC-VCO design that includes an SCA, a P-type Si-NWFET varactor, a 1.2 nH LC tank, and a bias network to linearize the varactor’s C-V characteristics, enabling a wide oscillation frequency tuning range. The circuit achieves a 24 GHz oscillation frequency with a low power consumption of 16.8 μW at a control voltage (Vctrl) of 0.7 V. Phase noise simulations indicate an excellent -109.62 dBc/Hz at a 1 MHz offset, confirming its applicability for RFIC systems. Additionally, the proposed LC-VCO demonstrates stable performance in five major corner process analyses, ensuring robustness under extreme conditions. These results validate the durability of the design and highlight the potential of Si-NWFETbased LC-VCOs as a viable, low-power, highly integrated solution for RFIC applications. The findings underscore the suitability of Si-NWFET technology as a promising alternative to current FinFET and CMOS processes in advanced circuit design.
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Synthesis Methods of Silver Sulfide for SWIR Region Applications
Yunhye Jeong, Gi-hwan Kim
J Electr Electron Mater 2024;37(4):374-381.   Published online July 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.4.3
This paper delves into the application of the short-wave infrared (SWIR) region, with a focus on the synthesis and optical characteristics of silver sulfide (Ag2S) nanostructures. SWIR offers advantages such as reduced damage to biological tissues and enhanced optical transparency, making it valuable across various domains. The study introduces three distinct synthesis methods, each showcasing the ability to obtain nanostructures with improved optical properties. These research findings open up the possibility of providing tailored solutions in detection, imaging, and other applications by controlling the size and ligands of Ag2S nanoparticles. This paper provides new insights into the utilization of Ag2S in the SWIR region, which is expected to foster advancements in future technologies.
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Analysis of Conductivity Variation and Conduction Mechanism in Bulk NiO Based on Sintering Conditions
Ju-hyeon Lee, Tae-soo Yeo, Wook Jo
J Electr Electron Mater 2023;36(4):418-421.   Published online July 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.4.15
Multilayer Ceramic Capacitors (MLCCs) are essential passive components in the electronics industry, known for their high capacitance due to the multilayer structure comprising inner electrodes and dielectric layers. Nickel electrodes are commonly used in MLCCs as the inner electrodes, and to prevent oxidation during the co-firing of the dielectric layers with nickel electrodes, reducing atmosphere is required. However, reducing atmosphere sintering can also induce a reduction of the dielectric, necessitating precise control of oxygen partial pressure. To explore the possibility of using oxide electrodes that do not require reducing atmosphere sintering, we analyze the electrical properties of nickel oxide (NiO) as a potential candidate. As a preliminary study on its use as an alternative inner electrode, the correlation between microstructure and electrical properties of bulk NiO under different sintering conditions was investigated to gain insights into the conduction mechanisms of the material.
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Thermodynamic Process Design of CaF2 Single Crystal Growth for Optical Applications
Seong-min Jeong, Hae-jin Jeon, Yun-ji Shin, Hyoung-seuk Choi, Si-young Bae
J Electr Electron Mater 2023;36(2):197-202.   Published online March 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.2.14
Calcium fluoride (CaF2) single crystal is applied to numerous industrial applications, especially for optical uses. To have excellent optical transmission properties, however, CaF2 crystals should be carefully fabricated through liquid-phase crystal growth techniques. In this study, as one of the early stage research activities to grow CaF2 crystals with a good transmittance at the ultraviolet wavelength range, computational thermodynamic models were provided to deepen the understanding of the crystal growing processes of CaF2 under various conditions. To remove point defects and oxygen impurities in the grown CaF2 crystals, the system was thermodynamically evaluated to get optimal process conditions. From the reviews of previous experimental studies, computational thermodynamic approaches were found to be an effective and powerful tool to understand the meaning of the crystal growth processes and to obtain optimal process conditions.
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Data Collection Management Program for Smart Factory
Hyeon-jin Kim, Jin-sa Kim
J Electr Electron Mater 2022;35(5):509-515.   Published online September 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.5.14
As the 4th industrial revolution based on ICT is progressing in the manufacturing field, interest in building smart factories that can be flexible and customized according to customer demand is increasing. To this end, it is necessary to maximize the efficiency of factory by performing an automated process in real time through a network communication between engineers and equipment to be able to link the established IT system. It is also necessary to collect and store real-time data from heterogeneous facilities and to analyze and visualize a vast amount of data to utilize necessary information. Therefore, in this study, four types of controllers such as PLC, Arduino, Raspberry Pi, and embedded system, which are generally used to build a smart factory that can connect technologies such as artificial intelligence (AI), Internet of Things (IoT), and big data, are configured. This study was conducted for the development of a program that can collect and store data in real time to visualize and manage information. For communication verification by controller, data communication was implemented and verified with the data log in the program, and 3D monitoring was implemented and verified to check the process status such as planned quantity for each controller, actual quantity, production progress, operation rate, and defect rate.
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Recent Progress in Dielectric Materials for MLCC Application
Intae Seo, Hyung-won Kang, Seung Ho Han
J Electr Electron Mater 2022;35(2):103-118.   Published online March 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.2.1
With the recent increase in demand for electronic devices, multi-layer ceramic capacitors (MLCCs) have become the most important core component. In particular, the next-generation MLCC with extremely high reliability is required for the 4th industrial revolution and electric vehicle applications. Therefore, it is necessary to develop dielectric ceramic materials with high dielectric properties and reliability. During the decades, electrical properties of BaTiO3 based dielectric ceramics, which have been widely used in MLCC industrial field, have been improved by microstructure and defect chemistry control. However, electrical properties of BaTiO3 have reached their limits, and new types of dielectric materials have been widely studied. Based on these backgrounds, this report presents the recent development trends of BaTiO3-based dielectric materials for the nextgeneration MLCCs, and suggests promising candidates to replace BaTiO3 ceramics.
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A Study on Building a Test Bed for Smart Manufacturing Technology
Choon-nam Cho
J Electr Electron Mater 2021;34(6):475-479.   Published online November 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.6.12
There are many difficulties in the applications of smart manufacturing technology in the era of the 4th industrial revolution. In this paper, a test bed was built to aim for acquiring smart manufacturing technology, and the test bed was designed to acquire basic technologies necessary for PLC (Programmable Logic Controller), HMI, Internet of Things (IoT), artificial intelligence (AI) and big data. By building a vehicle maintenance lift that can be easily accessed by the general public, PLC control technology and HMI drawing technology can be acquired, and by using cloud services, workers can respond to emergencies and alarms regardless of time and space. In addition, by managing and monitoring data for smart manufacturing, it is possible to acquire basic technologies necessary for embedded systems, the Internet of Things, artificial intelligence, and big data. It is expected that the improvement of smart manufacturing technology capability according to the results of this study will contribute to the effect of creating added value according to the applications of smart manufacturing technology in the future.
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First-Principles Calculations for Design of Efficient Electrocatalysts
Dong Yeon Kim
J Electr Electron Mater 2021;34(6):393-400.   Published online November 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.6.1
As the recent climate problems are getting worse year after year, the demands for clean energy materials have highly increased in modern society. However, the candidate material classes for clean energy expand rapidly and the outcomes are too complex to be interpreted at laboratory scale (e.g., multicomponent materials). In order to overcome these issues, the firstprinciples calculations are becoming attractive in the field of material science. The calculations can be performed rapidly using virtual environments without physical limitations in a vast candidate pool, and theory can address the origin of activity through the calculations of electronic structure of materials, even if the structure of material is too complex. Therefore, in terms of the latest trends, we report academic progress related to the first-principles calculations for design of efficient electrocatalysts. The basic background for theory and specific research examples are reported together with the perspective on the design of novel materials using first-principles calculations.
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A Study on Reliability of Liquid-Crystal for Smart Window
Byung-kyu Park, Sun-geum Kim, Seung-woo Lee, Gye-choon Park, Jin Lee
J Electr Electron Mater 2020;33(6):471-474.   Published online November 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.6.8
In recent years, the challenge of higher energy efficiency has emerged as urban buildings have become taller, and the area of window glasses has increased. To address the problem of energy efficiency in buildings, research on smart windows is being actively conducted. In this study, an accelerated experiment for thermal stability was conducted to fabricate a liquid crystal cell applicable to external windows. It was confirmed from the study that the function is maintained even in a high-temperature external environment through the change in transmittance by voltage. Compared with the initial transmittance, after the passage of time, the smart window cell to which the sealant was applied showed a small change in transmittance of 1~2%. This result confirmed the thermal stability of the liquid crystal-based smart window.
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Synthesis and Characterization of BaTiO3 Powder by Solid State Method
Yong Jin Kim, Moon Hee Choi, Hyo Soon Shin, Byeong-kwon Ju, Myoung Pyo Chun
J Electr Electron Mater 2020;33(6):483-489.   Published online November 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.6.10
BaTiO3 powder was synthesized by a solid-state reaction using BaCO3 and TiO2. Different calcination temperatures (800℃, 850℃, 900℃, and 950℃) were set to investigate their effects on the properties of BaTiO3 powder. The synthesized BaTiO3 phase was confirmed to be a single phase by XRD, and the tetragonality (c/a) and crystallite size were calculated. Thereafter, each calcinated BaTiO3 was sintered at five different sintering temperatures (1,100℃, 1,150℃, 1,200℃, 1,250℃, and 1,300℃), and the tetragonality, density, porosity, dielectric constant, and grain size were measured. As the calcination temperature increased, the tetragonality and crystallite size also increased, to 1.008 and 66 nm, respectively, at 950℃. Moreover, most pellets showed increased density, dielectric constant, and tetragonality as the sintering temperature increased up to 1,250℃; the same parameters slightly decreased at 1,300℃. It is noteworthy that the tetragonality of BaTiO3 at 1,250℃ exhibits a very high c/a value of 1.0084. In addition, the grain size and dielectric constant measured near the Curie temperature increased as the sintering temperature increased.
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Electrical Characteristics of and Temperature Distribution in Chalcogenide Phase Change Memory Devices Having a Self-Aligned Structure
Hye Ryeon Yoon, Young Sam Park, Seung-yun Lee
J Electr Electron Mater 2019;32(6):448-453.   Published online November 1, 2019
This work reports the electrical characteristics of and temperature distribution in chalcogenide phase change memory (PCM) devices that have a self-aligned structure. GST (Ge-Sb-Te) chalcogenide alloy films were formed in a self-aligned manner by interdiffusion between sputter-deposited Ge and Sb2Te3 films during thermal annealing. A transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) analysis demonstrated that the local composition of the GST alloy differed significantly and that a Ge2Sb2Te5 intermediate layer was formed near the Ge/Sb2Te3 interface. The programming current and threshold switching voltage of the PCM device were much smaller than those of a control device; this implies that a phase transition occurred only in the Ge2Sb2Te5 intermediate layer and not in the entire thickness of the GST alloy. It was confirmed by computer simulation, that the localized phase transition and heat loss suppression of the GST alloy promoted a temperature rise in the PCM device.
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PLC Optical Sensor for Contamination Monitoring on the Flow-Cell in the Water Quality Measurement System
Seung Heon Han, Tae Un Kim, Haeng Yun Jung, Hyun Chul Ki, Doo Gun Kim, Seon Hoon Kim
J Electr Electron Mater 2019;32(6):472-476.   Published online November 1, 2019
We have proposed a novel planar lightwave circuit (PLC) optical sensor to monitor the contamination in a flow-cell where water is continuously supplied through a water quality measurement system. We designed a PLC chip with a V-shape waveguide and the simulated its function as a sensor for monitoring contamination in a flow-cell using a numerical the FDTD (finite-difference time-domain) analysis. A novel cross type of waveguide was introduced to make the PLC chip of the V-shaped waveguide. The fabricated PLC was cut into the cross waveguide. A change in the optical propagation loss of the PLC sensor was observed after immersing the PLC sensor into city water. It was determined that the propagation loss of the PLC sensor was 3 dB at a wavelength of 1.55 μm in the city water for 15 days.
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Characteristics of Cu-Doped Ge8Sb2Te11 Thin Films for PRAM
Yeong-mi Kim, Heon Kong, Byung-cheul Kim, Hyun-yong Lee
J Electr Electron Mater 2019;32(5):376-381.   Published online September 1, 2019
In this work, we evaluated the structural, electrical and optical properties of Ge8Sb2Te11 and Cu-doped Ge8Sb2Te11 thin films prepared by rf-magnetron reactive sputtering. The 200-nm-thick deposited films were annealed in a range of 100~400℃ using a furnace in an N2 atmosphere. The amorphous-to-crystalline phase changes of the thin films were investigated by X-ray diffraction (XRD), UV-Vis-IR spectrophotometry, a 4-point probe, and a source meter. A one-step phase transformation from amorphous to face-centered-cubic (fcc) and an increase of the crystallization temperature (Tc) was observed in the Cu-doped film, which indicates an enhanced thermal stability in the amorphous state. The difference in the optical energy band gap (Eop) between the amorphous and crystalline phases was relatively large, approximately 0.38~0.41 eV, which is beneficial for reducing the noise in the memory devices. The sheet resistance(Rs) of the amorphous phase in the Cu-doped film was about 1.5 orders larger than that in undoped film. A large Rs in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage (Vth) was seen in the Cu-doped film, which implied a high thermal efficiency. This suggests that the Cu-doped Ge8Sb2Te11 thin film is a good candidate for PRAM.
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A Study on the Properties of Flame Retardant and Fire Safety of Silicone Rubbers Added Reinforcing Fillers
Seung Ho Park, Sung Ill Lee
J Electr Electron Mater 2019;32(4):349-355.   Published online July 1, 2019
A fire, be it caused intentionally or unintentionally, leads to economic loss and physical damage, and requires digestion. The number of fires is increasing yearly, and electrical fires account for more than 30% among the main causes of fires. Electric wires that catch fire typically employ silicone coatings; silicone has organic as well as inorganic properties. Silicon is a natural, nonexistent, synthetic product with numerous applications. In this study, a silicon rubber for application in wires was prepared by high-temperature vulcanization (HTV) with a Shore A hardness of 70. We report results for the flame retardancy test and the fire safety characteristics via inorganic analysis. For this, a quartz inorganic material was added to the wire specimen, and 18% powdered extinguishing agent ammonium phosphate and expanded vermiculite respectively. Thus, expanded vermiculite showed the best flame retardancy and fire safety characteristics.
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A Study on Flame Retardancy and Tracking Properties of Expanded Vermiculite Added Silicon Rubber for Wire
Seung Ho Park, Sung Ill Lee
J Electr Electron Mater 2019;32(3):213-218.   Published online May 1, 2019
In this study, a high-temperature vulcanizing (HTV) method was used to achieve a shore a hardness of 70. The basic base was composed of 60% silicon gum (GUM) which is a high-viscosity polymer, 30% fumed silica (FS), and 5% of plasticizer. The GUM and FS were mixed well with less than 1% silane to improve rubber strength. Expanded vermiculite was added as a filler at 10%, 15%, and 20%. The curing conditions were 170℃ for 10 min and a molding method was applied. We report herein, the results of inorganic analysis and flame-retardant and tracking tests on the expanded vermiculite. The flame retardance and tracking test outcomes for a shore a hardness of 70 were found to be optimal when the expanded vermiculite content was 10%.
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Piezoelectric Characteristics of Lead-Free 0.74(Bi0.5Na0.5)TiO3-0.26SrTiO3 Ceramics According to Calcination Temperature
Seong-hyun Kim, Sang-hun Lee, Hyoung-su Han, Jae-shin Lee
J Electr Electron Mater 2019;32(1):35-39.   Published online January 1, 2019
In this study, we investigated the optimum calcination temperature of lead-free 0.74(Bi0.5Na0.5)TiO3-0.26SrTiO3 (BNST) piezoelectric ceramics by analyzing the crystal structure, dielectric properties, and electric field-induced strain behavior. BNST ceramics prepared by conventional solid-state reaction methods at various calcination temperatures according to the industrial standard. All samples of BNST ceramics were subsequently sintered at 1,175℃ for 2 h. Crystal structure classification of the ceramics showed a single perovskite phase, with no second phase detectable for the samples calcined at 750℃ or higher. BNST samples calcined at 850℃ exhibited the most optimal values for itsand the common physical parameters of density = 5.518 g/㎤, ε = 1,871.837, tanδ = 0.047, and d33* = 874 pm/V.
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Efficiency Characteristics of DSSC Using TiO2 Paste for Low Temperature Annealing with TTIP
Sung Yeol Kwon, Chang Soo Sim, Wook Yang
J Electr Electron Mater 2019;32(1):53-57.   Published online January 1, 2019
Recently, the application field of solar panels is increasing. Accordingly, the demand for flexible devices is also steadily increasing. It is therefore necessary to develop TiO2 paste for low-temperature annealing for flexible DSSC fabrication. In this study, the TiO2 paste for low-temperature annealing with varying molar ratio of titanium isopropoxide (TTIP) was prepared, and DSSC was fabricated and its characteristics were compared. As a result, there was no deformation of the particles on the surface in the SEM data. However, the highest open circuit voltage, short circuit current, and fill factor were measured in the DSSC unit cell prepared by adding 0.5 mol of TTIP to the TiO2 paste, and the highest efficiency was 4.148%.
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A Study on Characterization of P-N Junction Using Silicon Direct Bonding
Won-chae Jung
J Electr Electron Mater 2017;30(10):615-624.   Published online October 1, 2017
This study investigated the various physical and electrical effects of silicon direct bonding. Direct bonding means the joining of two wafers together without an intermediate layer. If the surfaces are flat, and made clean and smooth using HF treatment to remove the native oxide layer, they can stick together when brought into contact and form a weak bond depending on the physical forces at room temperature. An IR camera and acoustic systems were used to analyze the voids and bonding conditions in an interface layer during bonding experiments. The I-V and C-V characteristics are also reported herein. The capacitance values for a range of frequencies were measured using a LCR meter. Direct wafer bonding of silicon is a simple method to fuse two wafers together; however, it is difficult to achieve perfect bonding of the two wafers. The direct bonding technology can be used for MEMS and other applications in three-dimensional integrated circuits and special devices.
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Glass Forming Stability in Chalcogenide-based GeSbSe Materials for IR-Lens
Gun-hong Jung, Heon Kong, Jong-bin Yeo, Hyun-yong Lee
J Electr Electron Mater 2017;30(4):204-209.   Published online April 1, 2017
Thermal and structural stability in the glass transition region of chalcogenide glasses has been investigated in terms of thermodynamics for application to various optoelectronic devices. In this study, the compositions of GexSb20Se80-x (x = 10, 15, 20, 25, and 30) were selected to investigate the glass stability according to germanium ratios. The chalcogenide bulks were fabricated by using a traditional melt-quenching method. Thin films were deposited by a thermal evaporation system, maintaining the deposition ratio of 3~5 A in order to have uniformity. The thermal and structural properties were measured by a differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The DSC analysis provided thermal parameters and theoretical glass region stabilities. The XRD analysis supported the theoretical stabilities because of where the crystallization peak data occurred.
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An Optical Analysis of Viewing-angle Switchable Display Using ELC Lens
Shin-yong Jeong, Woo-sang Park
J Electr Electron Mater 2017;30(4):241-245.   Published online April 1, 2017
This paper proposes a private display that can adjust viewing angles by using an electric-field-driven (EFD) LC Lens. The EFD LC Lens design and simulation were analyzed by using the Extended Jones Matrix Method. The conventional method for attaching a private film to the display was difficult. In order to solve this problem, in this study, by using the EFD LC Lens, we devised a method that can view images more conveniently. We analyzed the luminance and illumination of the optical viewing distance by using the Extended Jones Matrix Method. We also measured the intensity of the viewing angles. The simulation attached the EFD LC Lens to the 14" Full HD RGB stripe wide panel. We calculated the relative luminance distribution and the luminance distribution on the viewing angle of the image at the optimum viewing distance of 60 cm, using the EFD LC Lens and the lenticular lens. The proposed method could be used to design private displays that can adjust the viewing angle of the EFD LC Lens.
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Evaluation on the Phase-Change Properties in W-doped Ge8Sb2Te11 Thin Films for Amorphous-to-Crystalline Reversible Phase-Change Device
Cheol-jin Park, Jong-bin Yeo, Heon Kong, Hyun-yong Lee
J Electr Electron Mater 2017;30(3):133-138.   Published online March 1, 2017
We evaluated the structural, electrical and optical properties of tungsten (W)-doped Ge8Sb2Te11 thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve thermal stability. 200 mm thick Ge8Sb2Te11 and W-doped Ge8Sb2Te11 films were deposited on p-type Si (100) and glass substrates using a magnetron co-sputtering system at room temperature. The fabricated films were annealed in a furnace in the 0~400℃ temperature range. The structural properties were analyzed using X-ray diffraction (X`pert PRO, Phillips). The results showed increased crystallization temperature (Tc) leading to thermal stability in the amorphous state. The optical properties were analyzed using an UV-Vis-IR spectrophotometer (Shimadzu, U-3501, range : 300~3,000 nm). The results showed an increase in the crystalline material optical energy band gap (Eop) and an increase in the Eop difference (△Eop). This is a good effect to reduce memory device noise. The electrical properties were analyzed using a 4-point probe (CNT-series). This showed increased sheet resistance (Rs), which reduces programming current in the memory device.
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A Study on the Electrical Properties of MIM Structures Based on Ge2Sb2Te5 and Ge8Sb2Te11 Thin Films for ReRAM
Hwi-jong Jang, Heon Kong, Jong-bin Yeo, Hyun-yong Lee
J Electr Electron Mater 2017;30(3):144-147.   Published online March 1, 2017
In this study, Ge2Sb2Te5 and Ge8Sb2Te11 were used as an insulator layer to fabricate ReRAM devices. The resistance change is correlated to the appearance or disappearance of a conductivity filament at the surface of the GeSbTe layer. Changes in the electrical properties of ITO/GeSbTe/Ag devices were measured using a I-V-L measurement system. As a result, compared to the ITO/Ge8Sb2Te11/Ag device, this ITO/Ge2Sb2Te5/Ag ReRAM device exhibits highly uniform bipolar resistive switching characteristics, such as the operating voltages, and the resistance values.
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Rigorous Analysis of Viewing Zone for 3D Display with Electric-field-driven Liquid Crystal Lens
Tae Hyeon Kim, Bong Sik Kim, Woo Sang Park
J Electr Electron Mater 2016;29(8):494-498.   Published online August 1, 2016
In this paper, we proposed the 3-dimenstional (3D) analysis for calculating the optical characteristics of an autostereoscopic display with electric field driven liquid crystal (ELC) lens. From 3D analysis considering the slanting of lens, we calculate the cross-talk of each images and the distortion of viewing zone. Using geometric opics and extended Jones matrix method (EJMM), phase retardation of ELC lens according to position is calculated and then optical path difference in 3D space considering tilt and azimuth angle of incident light is gotten. Then, intensity distribution is presented in the space. Through camparing the intensity distribution using ideal lens with the ELC lens, we identify the noise and image distortion of ELC lens. As a result, this analysis is expected to provide optimum design conditions for realistic and rigorous 3D display with ELC lens.
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