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"Structure"

AI Algorithm for Stabilizing Output of Multi-Environment Double-Sided Solar Panels
Jongman Kim, Byonghak Moon, Changyong Jung, Sungjin Park
J Korean Inst Electr Electron Mater Eng 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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Effect of Interface Structure on the Efficiency Enhancement of Al-PDMS Triboelectric Nanogenerator
Dong-woo Hong, Wan-gon Hong, Seung-hun Kim, Sung-nam Lee
J Korean Inst Electr Electron Mater Eng 2025;38(1):107-112.   Published online January 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.1.15
Recent studies have focused on enhancing the efficiency of triboelectric nanogenerators (TENGs) using aluminum (Al) and polydimethylsiloxane (PDMS). This research investigates how surface morphology and material structure affect energy generation. By layering PDMS/Al and creating pyramid-shaped patterns, the study found that increasing the number of PDMS/Al layers significantly boosts the output voltage, reaching over 234 mV with three layers. Additionally, increasing the number of pyramid structures from 1 to 36 on PDMS surfaces, while maintaining the same contact area, led to a notable rise in generated voltage due to charge concentration at the pyramid tips. Higher pyramid angles also amplified this effect. These results highlight the importance of structural optimization in maximizing the energy output of TENGs, offering a promising route for more efficient energy harvesting.
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Controlled Synthesis of Colloidal Cu Nanowires and Nanoplates and Their Tunable Localized Surface Plasmon Resonances
Seokhwan Kim, Jong Wook Roh, Dong Choon Hyun, Seonhwa Park, Yuho Min
J Korean Inst Electr Electron Mater Eng 2024;37(5):547-553.   Published online September 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.5.12
Precise control over the morphology of nanostructures is critical for tailoring their physical and chemical properties. This study addresses the challenge of developing a simple, integrated method for synthesizing both 1D and 2D colloidal Cu nanostructures in a single system, achieving successful tuning of their localized surface plasmon resonance (LSPR) properties. A facile hydrothermal synthesis utilizing potassium iodide (KI) and hexadecylamine (HDA) is presented for controlling Cu nanostructure morphologies. The key to achieving 1D nanowires (NWs) and 2D nanoplates (NPs) depends on the controlled adsorption of HDA molecules and iodide (I-) ions on specific crystal facets. Depending on the morphologies, the resultant Cu nanostructures exhibit tunable LSPR peaks from 558 nm [nanoplates (NPs)] to 590 nm [nanowires (NWs)]. These results pave the way for the scalable and cost-effective production of plasmonic Cu nanostructures with tunable optical properties, holding promise for applications in sensing, catalysis, and photonic devices.

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  • Complexation-controlled Cu@Ag core-shell flakes for thermally stable printed electrodes in flexible energy-storage capacitors
    Seokhwan Kim, Geumseong Lee, Ye Chan Lee, Je-Hui Koo, Seonhwa Park, Geon-Tae Hwang, Mahesh Peddigari, Jungho Ryu, Dahye Shin, Kyoung Jin Jung, Kwi-Il Park, Yuho Min
    Chemical Engineering Journal.2026; 540: 177341.     CrossRef
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A Study on the Development of Nanorod-Type Ni-Rich Cathode Materials by Using Co-Precipitation Method
Joohyuk Park
J Korean Inst Electr Electron Mater Eng 2024;37(2):215-222.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.14
Ni-rich cathode materials have been developed as the most promising candidates for next-generation cathode materials for lithium-ion batteries because of their high capacity and energy density. In particular, the electrochemical performance of lithium-ion batteries could be enhanced by increasing the contents of nickel ion. However, there are still limitations, such as low structural stability, cation mixing, low capacity retention and poor rate capability. Herein, we have successfully developed the nanorod-type Ni-rich cathode materials by using co-precipitation method. Particularly, the nanorod-type primary particles of LiNi0.7Co0.15Mn0.15O2 could facilitate the electron transfer because of their longitudinal morphology. Moreover, there were holes at the center of secondary particles, resulting in high permeability of the electrolyte. Lithium-ion batteries using the prepared nanorod-type LiNi0.7Co0.15Mn0.15O2 achieved highly improved electrochemical performance with a superior rate capability during battery cycling.

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  • Thermal Stability of NCM622 Cathode Material for Li-ion Batteries: A Real-time Synchrotron X-ray Scattering Study
    Seung-Han Lee, Tae-Sik Cho
    Journal of Electrical and Electronic Materials.2026; 39(4): 394.     CrossRef
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High Energy Density Dielectric Ceramics Capacitors by Aerosol Deposition
Hyunseok Song, Geon Lee, Jiwon Ye, Ji Yun Jung, Dae-yong Jeong, Jungho Ryu
J Korean Inst Electr Electron Mater Eng 2024;37(2):119-132.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.1
Dielectric ceramic capacitors present high output power density due to the fast energy charge and discharge nature of dielectric polarization. By forming dense ceramic films with nano-grains through the Aerosol Deposition (AD) process, dielectric ceramic capacitors can have high dielectric breakdown strength, high energy storage density, and leading to high power density. Dielectric capacitors fabricated by AD process are expected to meet the increasing demand in applications that require not only high energy density but also high power output in a short time. This article reviews the recent progress on the dielectric ceramic capacitors with improved energy storage properties through AD process, including energy storage capacitors based on both leadbased and lead-free dielectric ceramics.

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  • Single-Molecule Manipulation Techniques Based on Mechanical, Electrical, and Structural Control
    Jeong Hun Shin, Tae Won Nam
    Journal of Electrical and Electronic Materials.2026; 39(3): 247.     CrossRef
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A Brief Review on Piezoelectrics-Based Paint Sensors
Hyoung-su Han, Trang An Duong, Chang Won Ahn, Byeong Woo Kim, Jae-shin Lee
J Korean Inst Electr Electron Mater Eng 2023;36(5):433-441.   Published online September 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.5.2
Piezoelectric ceramics play an important role in electrical and electronic devices such as sensors, actuators, and microelectronic devices. However, traditional ceramics are difficult to be used in various process industries due to their high brittleness and low flexibility. Therefore, piezoelectric paint sensors have been designed for application to the curved surfaces of complicated structures. Furthermore, recently, significant attention has been focused on the development of paint sensors that can be used as structure health monitoring sensors for vibration, impact, and acoustic emission. Several studies have successfully demonstrated the possibility that smart paint sensors can take the place of traditional ceramic sensors. In this review, we briefly introduce the concept of the piezoelectric paint sensors and the expected application field as well as their preparation and history.
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Analysis of Power Pattern According to Load Types
Mi-yong Hwang, Seung-joon Cho, Soon-hyung Lee, Yong-sung Choi
J Korean Inst Electr Electron Mater Eng 2023;36(4):369-375.   Published online July 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.4.7
In this paper, we compared and analyzed the power load patterns of dormitory buildings and office buildings to use them as basic data (demand analysis and capacity design) for the design and operation of microgrids for multi-use facilities, and the following conclusions were got. During the daytime on regular weekdays, the power consumption load pattern of office buildings was relatively large at 264.0~332.3 kWh, and during the evening hours, the power consumption load pattern of dormitory buildings was relatively large at 233.0~258.3 kWh. In the case of vacation, during the daytime on weekdays, the power consumption load pattern of office buildings was relatively large at 279.1~407.4 kWh, and in the evening, the power consumption load pattern of dormitory buildings was relatively high at 280.1~394.1 kWh. During the daytime on regular weekends, the power consumption of dormitory-type buildings was relatively high at 133.5~201.6 kWh, and it was found that the power consumption of dormitory-type buildings appeared relatively high at 187.5~252.1 kWh. During a vacation in the daytime on weekends, the power consumption of dormitory-type buildings was found to be 186.5 kWh~ and 218.6 kWh. The increase in power consumption during a vacation (December-February) compared to normal (April-June) was thought to be due to an increase in electricity demand, and the reason for the higher power consumption in dormitory buildings during the vacation was due to reduced working hours in office buildings.
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Synthesis and Characterization of Au@TiO2 Core-Shell Microspheres
Sun-Geum Kim, Ha Jun Jang, Jaewon Jang, Jae-hyun Shim, Sung-june Baek
J Korean Inst Electr Electron Mater Eng 2022;35(4):392-397.   Published online July 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.4.12
We present the structural and optical properties of Au@TiO2 core-shell microsphere structure prepared by a hydrothermal synthesis method. As a way to improve the efficiency of organic solar cells, the Au@TiO2 core-shell microsphere was synthesized to use the local surface plasmon resonance (LSPR) phenomenon. The synthesized results were confirmed to have the Au@TiO2 core-shell structure using a high-resolution transmission electron microscopy. An absorption was observed to occur at 527 nm belonging to the visible light region using a visible light spectroscopy, which supports the LSPR phenomenon. We suggest that the Au@TiO2 core-shell microsphere is highly likely to be applied to organic solar cells including dye-sensitized solar cells. In addition, we expect it to be widely used not only in the energy but also in the bio as well as in the environmental fields.
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Recent Progress in Dielectric Materials for MLCC Application
Intae Seo, Hyung-won Kang, Seung Ho Han
J Korean Inst Electr Electron Mater Eng 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 the Electrical Characteristics of Ge2Sb2Te5/Ti/W-Ge8Sb2Te11 Structure for Multi-Level Phase Change Memory
Woo-young Oh, Hyun-yong Lee
J Korean Inst Electr Electron Mater Eng 2022;35(1):44-49.   Published online January 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.1.7
In this paper, we investigated current (I)- and voltage (V)-sweeping properties in a double-stack structure, Ge2Sb2Te5/Ti/W-doped Ge8Sb2Te11, a candidate medium for applications to multilevel phase-change memory. 200-nm-thick Ge2Sb2Te5 and W-doped Ge8Sb2Te11 films were deposited on p-type Si(100) substrate using magnetron sputtering system, and the sheet resistance was measured using 4 point-probe method. The sheet resistance of amorphous-phase W-doped Ge8Sb2Te11 film was about 1 order larger than that of Ge2Sb2Te5 film. The I- and V-sweeping properties were measured using sourcemeter, pulse generator, and digital multimeter. The speed of amorphous-to-multilevel crystallization was evaluated from a graph of resistance vs. pulse duration (t) at a fixed applied voltage (12 V). All the double-stack cells exhibited a two-step phase change process with the multilevel memory states of high-middle-low resistance (HR-MR-LR). In particular, the stable MR state is required to guarantee the reliability of the multilevel phase-change memory. For the Ge2Sb2Te5 (150 nm)/Ti (20 nm)/WGe8Sb2Te11 (50 nm), the phase transformations of HR→MR and MR→LR were observed at t<30ns and t<65ns, respectively. We believe that a high speed and stable multilevel phase-change memory can be optimized by the double-stack structure of proper Ge-Sb-Te films separated by a barrier metal (Ti).
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A Study on Polymer Replica Materials for Nanotransfer Printing
Young Lim Kang, Woon Ik Park
J Korean Inst Electr Electron Mater Eng 2021;34(4):262-268.   Published online July 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.4.262
For the past several decades, various next-generation patterning methods have been developed to obtain well-designed nano-to-micro structures, such as imprint lithography, nanotransfer printing (nTP), directed self-assembly (DSA), E-beam lithography, and so on. Especially, nTP process has much attention due to its low processing cost, short processing time, and good compatibility with other patterning techniques in achieving the formation of high-resolution functional patterns. To transfer functional patterns onto desirable substrates, the use of soft materials is required for precise replication of master mold. Here, we introduce a simple and practical nTP method to create highly ordered structures using various polymeric replica materials. We found that polymethyl methacrylate (PMMA), polystyrene (PS), and polyvinylpyridine (PVP) are possible candidates for replica materials for reliable duplication of Si master mold based on systematic analysis of pattern visualization. Furthermore, we successfully obtained well-defined metal and oxide nanostructures with functionality on target substrates by using replica patterns, through deposition and transfer process. We expect that the several candidates of replica materials can be exploited for effective nanofabrication of complex electronic devices.
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The Formation of Anodic Oxide Film by Anodizing Voltage and Time of 6061 Aluminum Alloy
Youngju Park, Chanyoung Jeong
J Korean Inst Electr Electron Mater Eng 2021;34(1):68-72.   Published online January 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.1.068
Aluminum is a lightweight metal and has excellent properties with regard to conductivity, workability, and strength. It has been used in various industries owing to its economic benefits. To improve upon the mechanical properties and processability by adding various alloying elements to aluminum, improving the corrosion resistance and heat resistance by electrochemically forming a porous anodic film having a thickness and hardness on the surface of the aluminum alloy is crucial. In this study, the aluminum 6061 alloy was controlled by an anodization process in a 0.3M oxalic acid electrolyte at room temperature to investigate the oxide film parameters such as porosity and thickness depending on the modulating applied voltage and time. The anodizing experiment was performed by increasing the time from 1 h to 9 h at 2-h intervals at applied voltages of 50 V and 60 V.
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Study on Formation of Semitransparent Cu Nanoparticle Layers for Realizing Metal Nanoparticle-Dielectric Bilayer Structures
Hye Ryeon Yoon, Yoon Ee Jo, Hoi Jin Yoon, Seung-yun Lee
J Korean Inst Electr Electron Mater Eng 2020;33(6):460-464.   Published online November 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.6.6
This study reports the fabrication and application of semitransparent Cu nanoparticle layers. Spin coating and subsequent drying of a Cu colloid solution were performed to deposit Cu nanoparticle layers onto Si and glass substrates. As the spin speed of the spin coating increases, the density of the nanoparticles on the substrate decreases, and the agglomeration of nanoparticles is suppressed. This microstructural variation affects the optical properties of the nanoparticle layers. The transmittance and reflectance of the Cu nanoparticle layers increase with increasing spin speed, which results from the trade-off between the exposed substrate area and surface coverage of the Cu nanoparticles. Since the glass substrates coated with Cu nanoparticle layers are semitransparent and colored, it is anticipated that the application of a Cu nanoparticle-dielectric bilayer structure to transparent solar cells will improve the cell efficiency as well as aesthetic appearance.
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Process Development for Enhancement of High Temperature Thermoelectric Properties in a p-Type Skutterudite
Peng Ju Liu, Chang Wan Nou, Soon-mok Choi
J Korean Inst Electr Electron Mater Eng 2020;33(6):495-499.   Published online November 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.6.12
Power factor improvement at high temperatures has been a major research topic for the development of skutterudite thermoelectric materials. Here, we attempted to optimize the process parameters for manufacturing skutterudite materials, especially for p-type systems. We focused on the effect of aging time variation to maximize the hightemperature performance of the Ce-filled Fe3CoSb12 skutterudite system. The optimized aging time was concluded to be a key parameter for the formation of single-phase nanostructures in this p-type skutterudite system. The optimized condition was effective in reducing the bipolar effect at high temperature ranges by increasing the carrier concentration in the p-type system. To confirm the conclusions, the electrical conductivity, Seebeck coefficient, and power factor were measured. The results matched well with the microstructure and with those of an XRD analysis performed for the system.
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Characteristics of SiO2 Based Asymmetric Multilayer Thin Films for High Performance Flexible Transparent Electrodes
Ji-won Jeong, Heon Kong, Hyun-yong Lee
J Korean Inst Electr Electron Mater Eng 2020;33(1):25-30.   Published online January 1, 2020
DOI: https://doi.org/10.4313/JKEM.2021.33.1.6
Oxide (SiO2)/Metal(Ag)/Oxide(SiO2, ITO, ZnO) multilayer films were fabricated using a magnetron sputtering technique at room temperature on Si (p-type, 100) and a glass substrate. The electrical and optical properties of the asymmetric multilayer films depended on the thickness of the mid-layer film and the type of oxide in the bottom layer. As the metal layer becomes thicker, the sheet resistance decreases. However, the transmittance decreases when the metal layer exceeds a threshold thickness of approximately 10~12 nm. In addition, the sheet resistance and transmittance change according to the type of oxide in the bottom layer. If the oxide has a large resistivity, the overall sheet resistance increases. In addition, the anti-reflection effect changes according to the refractive index of the oxide material. The optical and electrical properties of multilayer films were investigated using an ultraviolet visible (UV-Vis) spectrophotometer and a 4-point probe, respectively. The optimum structure is SiO2 (30 nm)/Ag (10 nm)/ZnO (30 nm) multilayer, with the highest FOM value of 7.7×10-3 Ω-1.
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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 Korean Inst Electr Electron Mater Eng 2019;32(6):448-453.   Published online November 1, 2019
DOI: https://doi.org/10.4313/JKEM.2019.32.6.448
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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Electromagnetic Property of a Heavy Fermion CePd2Si2
Tae Seong Jeong
J Korean Inst Electr Electron Mater Eng 2019;32(5):399-402.   Published online September 1, 2019
DOI: https://doi.org/10.4313/JKEM.2019.32.5.399
The electromagnetic properties of heavy fermion CePd2Si2 are investigated using density functional theory using the local density approximation (LDA) and LDA+U methods. The Ce f-bands are located near the Fermi energy and hybridized with the Pd-3d states. This hybridization plays an important role in generating the physical characteristics of this compound. The magnetic moment of CePd2Si2 calculated within the LDA scheme does not match with the experimental result because of the strong correlation interaction between the f orbitals. The calculation shows that the specific heat coefficient underestimates the experimental value by a factor of 5.98. This discrepancy is attributed to the formation of quasiparticles. The exchange interaction between the local f electrons and the conduction d electrons is the reason for the formation of quasiparticles. The exchange interaction is significant in CePd2Si2, which makes the quasiparticle mass increase. This enhances the specific heat coefficient.
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Design of Electrode Structure for Reducing Ag Paste for Shingled PV Module Application
Won Je Oh, Ji Su Park, Jae Hyeong Lee
J Korean Inst Electr Electron Mater Eng 2019;32(4):267-271.   Published online July 1, 2019
DOI: https://doi.org/10.4313/JKEM.2019.32.4.267
A shingled PV module is manufactured by dividing and bonding. In this method, the solar cell is divided by lasers and bonded using electrically conductive adhesives (ECAs). Consequently, the manufacturing cost increases because a process step is added. Therefore, we aim to reduce the production cost by reducing the amount of Ag paste used in the solar cell front. Various electrode structures were designed and simulated. The number of fingers was optimized by designing thinner fingers, and the number of fingers with the maximum power conversion efficiency was confirmed. The simulation confirmed the maximum efficiency in the 4-divided electrode pattern. The amount of Ag paste used for each electrode pattern was calculated and analyzed. The number of fingers was optimized by decreasing the width of the finger; this will not only reduce the amount of Ag paste required but also the increase the efficiency.
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Structural and Electrical Properties of BiFeO3 Thin Films by Eu and V Co-Doping
Sung-keun Chang, Youn-jang Kim
J Korean Inst Electr Electron Mater Eng 2019;32(3):229-233.   Published online May 1, 2019
DOI: https://doi.org/10.4313/JKEM.2019.32.3.229
Pure BiFeO3 (BFO) and (Eu, V) co-doped Bi0.9Eu0.1Fe0.975V0.025O3+δ (BEFVO) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by chemical solution deposition. The effects of co-doping were observed by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). The electrical properties of the BEFVO thin film were improved as compared to those of the pure BFO thin film. The remnant polarization (2Pr) of the BEFVO thin film was approximately 26 μC/cm2 at a maximum electric field of 1,190 kV/cm with a frequency of 1 kHz. The leakage current density of the co-doped BEFVO thin film (4.81×10-5 A/cm2 at 100 kV/cm) was two orders of magnitude lower than of that of the pure BFO thin film.
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A Study on the Electrical and Optical Properties of SnO2/Cu(Ni)/SnO2 Multi-Layer Structures Transparent Electrode According to Annealing Temperature
Ji-won Jeong, Heon Kong, Hyun-yong Lee
J Korean Inst Electr Electron Mater Eng 2019;32(2):134-140.   Published online March 1, 2019
DOI: https://doi.org/10.4313/JKEM.2019.32.2.134
Oxide (SnO2)/metal alloy (Cu(Ni))/oxide (SnO2) multilayer films were fabricated using the magnetron sputtering technique. The oxide and metal alloy were SnO2 and Ni-doped Cu, respectively. The structural, optical, and electrical properties of the multilayer films were investigated using X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectrophotometry, and 4-point probe measurements, respectively. The properties of the SnO2/Cu(Ni)/SnO2 multilayer films were dependent on the thickness and Ni doping of the mid-layer film. Since Ni atoms inhibit the diffusion and aggregation of Cu atoms, the grain growth of Cu is delayed upon Ni addition. For 250℃, the Haccke’s figure of merit (FOM) of the SnO2 (30 nm)/Cu(Ni) (8 nm)/SnO2 (30 nm) multilayer film was evaluated to be 0.17×10-3 Ω-1.
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Microstructures and Electrical Properties of PSN-PZT Ceramics for Piezoelectric Speaker
Sung-jin Kim, Soon-yong Kweon
J Korean Inst Electr Electron Mater Eng 2019;32(2):110-115.   Published online March 1, 2019
DOI: https://doi.org/10.4313/JKEM.2019.32.2.110
Pb(Sb0.5Nb0.5)x(Zr0.51Ti0.49)1-xO3 (abbreviation: PSN-PZT) ceramics were synthesized, using conventional bulk ceramic processing technology, with various PSN doping contents. The maximum density of PSN-PZT was 97% of the theoretical density in the samples sintered at 1,250℃. The maximum values of the piezoelectric properties achieved using the conventional processes were: kp of 0.625, d33 of 531 pC/N, and g33 of 33 mV·m/N. Finally, we fabricated a piezo-speaker with the optimized PSN-PZT ceramics. The SPL of the speaker was measured at a distance of 1 m, with a driving voltage of 40 Vrms in the frequency range of ~300 Hz to 9 kHz. The measured SPLmax was at a very high level (95 dB), which was superior in quality in comparison with those of other commercial products.
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Observation of Ferroelectric Domain Evolution Processes of Pb(Zr,Ti)O3 Ceramic Using Piezoresponse Force Microscopy
Kwanlae Kim
J Korean Inst Electr Electron Mater Eng 2019;32(1):20-24.   Published online January 1, 2019
DOI: https://doi.org/10.4313/JKEM.2019.32.1.20
Ferroelectric material properties are strongly governed by domain structures and their evolution processes, but the evolution processes of complex domain patterns during a macroscopic electrical poling process are still elusive. In the present work, domain-evolution processes in a PZT ceramic near the morphotropic phase-boundary composition were studied during a step-wise electrical poling using piezoresponse force microscopy (PFM). Electron backscatter diffraction was used with the PFM data to identify the grain boundaries in the region of interest. In response to an externally the applied electric field, growth and retreat of non-180° domain boundaries wasere observed. The results indicate that ferroelectric polarization-switching nucleates and evolves in concordance with the pattern of the pre-existing domains.
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Effect of PDMS Index Matching Layer on Characteristics of Mn-Doped SnO2 (MTO)/Ag/MTO/PDMS/MTO Transparent Electrode
Young-su Jo, Gun-eik Jang
J Korean Inst Electr Electron Mater Eng 2018;31(6):408-411.   Published online September 1, 2018
DOI: https://doi.org/10.4313/JKEM.2018.31.6.408
We fabricated highly flexible Mn-doped SnO2 (MTO)/Ag/MTO/polydimethylsiloxane (PDMS)/MTO multilayer transparent conducting films. To reduce refractive-index mismatching of the MTO/Ag/MTO/polyethylene terephthalate (PET), index-matching layers were inserted between the oxide-metal-oxide-structured films and the PET substrate. The PDMS layer was deposited by spin-coating after adjusting the mixing ratio of PDMS and hexane. We investigated the effects of the index-matching layer on the color and reflectance differences with different PDMS dilution ratios. As the dilution ratio increased from 1:100 to 1:130, the color difference increased slightly, while the reflectance difference decreased from 0.62 to 0.32. The MTO/Ag/MTO/PDMS/MTO film showed a transmittance of 87.18~87.68% at 550 nm. The highest value of the Haacke figure of merit was 47.54×10-3 Ω-1 for the dilution ratio of 1:130.
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Dielectric Properties of K(Ta0.6Nb0.4)O3 Thin Films Prepared by Sol-Gel Method for Microwave Applications
Min-su Kwon, Sung-gap Lee, Kyeong-min Kim, Sam-haeng Lee, Young-gon Kim
J Korean Inst Electr Electron Mater Eng 2018;31(6):403-407.   Published online September 1, 2018
DOI: https://doi.org/10.4313/JKEM.2018.31.6.403
In this study, double layer KTN/STO thin films were fabricated on Pt/Ti/SiO2/Si substrate, their structural and electrical properties were measured according with the number of STO coatings, and their applicability to microwave materials was investigated. The average grain size was about 80~90 nm, the average thickness of the 6-coated KTN thin film was about 320 nm, and the average thickness of the STO thin film coated once was about 45~50 nm. The dielectric constant decreased with increasing frequency, and as the number of STO coatings increased, the rate of change of the dielectric constant with the applied electric field decreased. The tunability of the KTN thin film showed a maximum value of 19.8% at 3 V. The figure of merit of the KTN/1STO thin film was 9.8 at 3 V.
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Optimization of Solar Cell Electrode Structure for Shingled Module
Won Je Oh, Ji Su Park, Soo Hyun Hwang, Su Ho Lee, Chae Hwan Jeong, Jae Hyeong Lee
J Korean Inst Electr Electron Mater Eng 2018;31(5):290-294.   Published online July 1, 2018
DOI: https://doi.org/10.4313/JKEM.2018.31.5.290
The shingled photovoltaic module can be produced by joining divided solar cells into a string of busbarless structure and arranging them in series and parallel to produce a module, in order to produce a high output per unit area. This paper reports a study to optimize solar cell electrode structure for shingled photovoltaic module fabrication. The characteristics of each electrode structure were analyzed according to the simulation program as follow: 80.62% fill factor in the six-junction solar cell electrode structure and 19.23% efficiency in the five-junction electrode structure. Therefore, the split electrode structure optimized for high-density and high-output shingled module fabrication is the five-junction solar cell electrode structure.
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Structural and Electrical Properties of Bi0.9A0.1Fe0.975Zn0.025O3-δ (A=Eu, Dy) BiFeO3 Thin Films by Chemical Solution Deposition
Youn-jang Kim, Jin-won Kim, Sung-keun Chang
J Korean Inst Electr Electron Mater Eng 2018;31(4):226-230.   Published online May 1, 2018
DOI: https://doi.org/10.4313/JKEM.2018.31.4.226
Pure BiFeO3 (BFO) and codoped Bi0.9A0.1Fe0.975Zn0.025O3-δ (A=Eu, Dy) thin films were prepared on Pt(111)/ Ti/SiO2/Si(100) substrates by chemical solution deposition. The remnant polarizations (2Pr) of the Bi0.9Eu0.1Fe0.975Zn0.025O3-δ (BEFZO) and Bi0.9Dy0.1Fe0.975Zn0.025O3-δ (BDFZO) thin films were about 36 and 26 μC/cm2 at the maximum electric fields of 900 and 917 kV/cm, respectively, at 1 kHz. The codoped BEFZO and BDFZO thin films showed improved electrical properties, and leakage current densities of 3.68 and 1.21×10-6 A/cm2, respectively, which were three orders of magnitude lower than that of the pure BFO film, at 100 kV/cm.
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Design of 1,200 V Class High Efficiency Trench Gate Field Stop IGBT with Nano Trench Gate Structure
Ey Goo Kang
J Korean Inst Electr Electron Mater Eng 2018;31(4):208-211.   Published online May 1, 2018
DOI: https://doi.org/10.4313/JKEM.2018.31.4.208
This paper details the design of a 1,200 V class trench gate field stop IGBT (insulated gate bipolar transistor) with a nano gate structure smaller than 1 um. Decreasing the size is important for lowering the cost and increasing the efficiency of power devices because they are high-voltage switching devices, unlike memory devices. Therefore, in this paper, we used a 2-D device and process simulations to maintain a gate width of less than 1 um, and carried out experiments to determine design and process parameters to optimize the core electrical characteristics, such as breakdown voltage and on-state voltage drop. As a result of these experiments, we obtained a wafer resistivity of 45 Ω·cm, a drift layer depth of more than 180 um, an N+ buffer resistivity of 0.08, and an N+ buffer thickness of 0.5 um, which are important for maintaining 1,200 V class IGBTs. Specially, it is more important to optimize the resistivity of the wafer than the depth of the drift layer to maintain a high breakdown voltage for these devices.
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Study on Surface Plasmon Electrode Using Metal Nano-Structure for Maximizing Sterilization of Dielectric Discharge
Hyun-chul Ki, Byeong-yun Oh
J Korean Inst Electr Electron Mater Eng 2018;31(2):80-84.   Published online February 1, 2018
DOI: https://doi.org/10.4313/JKEM.2018.31.2.80
In this study, we investigated plasmon effects to maximize the sterilization of dielectric discharge. We predicted the effect using the finite difference time domain (FDTD) method as a function of electrode shape, size, and period. The structure of the electrode was designed with a thickness of 100 nm of silver nanoparticles on a glass substrate, and was varied according to the shape, size, and period of the electrode hole. Based on the results, it was confirmed that the effect of plasmons was independent of the shape of the electrode hole. It was thus confirmed that the plasmon effect depended only on the size and period of the holes. Further, the plasmon effect was affected by the size rather than period of the holes. Because the absorption of light by the metal varied according to the size of the hole, the plasmon effect generated by the absorption of light also varied. The best results were obtained when the radius and period of the electrode holes were 0.1 μm and 0.4 μm, respectively.
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Microstructural and Electrical Properties of Bi0.9A0.1Fe0.975V0.025O3+α(A=Nd, Tb) Thin Films by Chemical Solution Deposition Method
Sung-keun Chang, Youn-jang Kim
J Korean Inst Electr Electron Mater Eng 2017;30(10):646-650.   Published online October 1, 2017
DOI: https://doi.org/10.4313/JKEM.2017.30.10.646
We have evaluated the ferroelectric and electrical properties of pure BiFeO3 (BFO) and Bi0.9A0.1Fe0.975V0.025O3+α(A=Nd, Tb) thin films on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. The remnant polarization (2Pr) of the Bi0.9Tb0.1Fe0.975V0.025O3+α (BTFVO) thin film was approximately 65 μC/㎠, with a maximum applied electric field of 950 kV/cm and a frequency of 10 kHz, where as that of the Bi0.9Nd0.1Fe0.975V0.025O3+α (BNFVO) thin film was approximately 37 μC/㎠ with a maximum applied electric field of 910 kV/cm. The leakage current density of the co-doped BNFVO thin film was four orders of magnitude lower than that of the pure BFO thin film, at 2.75×10-7 A/㎠ with an applied electric field of 100 kV/cm. The grain size and uniformity of the co-doped BNFVO and BTFVO thin films were improved, in comparison to the pure BFO thin film, through structural modificationsdue to the co-doping with Nd and Tb.
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Effect of Porcelain/Polymer Interface on the Microstructure, Insulation Characteristics and Electrical Field Distribution of Hybrid Insulators
Jun-young Cho, Woo-seok Kim, Ho-sung An, Hee-sung An, Tae-wan Kim, Yun-seog Lim, Sung-hwan Bae, Chan Park
J Korean Inst Electr Electron Mater Eng 2017;30(9):558-565.   Published online September 1, 2017
DOI: https://doi.org/10.4313/JKEM.2017.30.9.558
Hybrid insulators that have the advantages of both porcelain (high mechanical strength and chemical stability) as well as polymer (light weight and high resistance to pollution) insulators, can be used in place of individual porcelain and polymer insulators that are used for both mechanical support as well as electrical insulation of overhead power transmission lines. The most significant feature of hybrid insulators is the presence of porcelain/polymer interfaces where the porcelain and polymer are physically bonded. Individual porcelain and polymer insulators do not have such porcelain/polymer interfaces. Although the interface is expected to affect the mechanical/electrical properties of the hybrid insulator, systematic studies of the adhesion properties at the porcelain/polymer interface and the effect of the interface on the insulation characteristics and electric field distribution of the hybrid insulator have not been reported. In this study, we fabricated small hybrid insulator specimens with various types of interfaces and investigated the effect of the porcelain/polymer interface on the microstructure, insulating characteristics, and electric field distribution of the hybrid insulators. It was observed that the porcelain/polymer interface of the hybrid insulator does not have a significant effect on the insulating characteristics and electric field distribution, and the hybrid insulator can exhibit electrical insulating properties that are similar or superior to those of individual porcelain and polymer insulators.
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