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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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To ensure the long-term reliability of flexible photovoltaic (FPV) modules, it is crucial to develop an effective moisture barrier layer that prevents the infiltration of moisture and oxygen. We developed such a layer composed of parylene (700 nm) and AlOx (70 nm), optimizing its material properties, moisture-blocking performance, and processing conditions. The barrier layer applied to the Ethylene Tetrafluoroethylene (ETFE) substrate demonstrated a water vapor transmission rate (WVTR) of 6.33 × 10-2 g/m²/day and an average visible light transmittance (AVT) of 85.3% over the 380-780 nm wavelength range. For the FPV module with this barrier, Damp/Heat (DH) reliability testing was conducted at 85℃ and 85% relative humidity for up to 1,000 hours. During testing, the power conversion efficiency (PCE) decreased slightly from 25.4% (0 hr) to 24.7% (1,000 hr), reflecting a minimal reduction of only 0.7%. The primary cause of degradation was identified as a -4% relative change in shortcircuit current density (JSC) before and after DH testing. Consequently, the ETFE/parylene/AlOx multilayer moisture barrier proved highly effective in ensuring the long-term reliability of solar modules.
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The mounting demand for sustainable, self-powered biomedical devices, particularly those engineered for extreme environments, has established triboelectric nanogenerators (TENGs) as a prominent technology in energy harvesting research. This review examines state-of-the-art biomaterial synthesis strategies essential for developing high-performance bioelectronic TENGs that can operate reliably under harsh conditions, including elevated temperatures, extreme humidity, and mechanical strain. It begins with a comprehensive overview of the fundamental principles of triboelectricity and subsequently addresses the pivotal challenges associated with efficient charge generation and retention in such challenging settings. The content places particular emphasis on recent advancements in composite material engineering and structure design for high-efficiency mechanisms, with a particular focus on biocompatible and environmentally resilient materials. The integration of TENGs into wearable sensors, implantable devices, and self-powered monitoring systems is also investigated, demonstrating their transformative potential for bioelectronic applications. Our goal subsequently underscores persistent limitations to overcome, including those pertaining to fabrication scalability and long-term operational stability, while concurrently proposing prospective research directions. Consequently, this work underscores how innovative biomaterial synthesis and bioelectronic devices can enable the development of next-generation, high-performance, self-powered devices suited for extreme biomedical environments.
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Improved Electrical Stability of In₂O₃ Thin-Film Transistors Through Temperature-Controlled H₂O₃ Processes
Jeong Hun Choi, Jae-yun Lee, Beom Gu Lee, Jeong Moo Seo, Sung-jin Kim
J Electr Electron Mater 2025;38(4):418-424.   Published online July 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.4.10
In this study, we investigated the electrical stability and performance enhancement of In₂O₃ thin-film transistors (TFTs) through hydrogen peroxide (H₂O₂) and ultraviolet (UV) treatment under controlled temperature conditions. The In₂O₃ TFTs were fabricated using a sol-gel process, followed by H₂O₂ treatment at 40, 50, and 60℃ in combination with UV irradiation. The impact of these processing conditions on the device characteristics, including mobility (μ), threshold voltage (Vth), subthreshold swing (S/S), and on/off current ratio, was systematically analyzed. The results indicate that the 50℃ TFTs exhibited the most stable electrical performance, with minimal Vth shift under negative bias stress (NBS) conditions and optimized switching behavior. Furthermore, static inverter measurements confirmed the reliable voltage transfer characteristics (VTCs) and gain performance of the optimized In₂O₃ TFTs. These findings suggest that the proposed H₂O₂ and UV treatment technique can effectively improve the reliability and long-term stability of In₂O₃-based electronic devices, making them promising candidates for future electronic applications.
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Van der Waals Integration of Dielectrics and Metal Contacts with Two-Dimensional Semiconductors for Emerging Nanoelectronics
Dahyeon Park, Habin Baek, Changjun Park, Chanho Lee, Joonki Suh
J Electr Electron Mater 2025;38(3):233-246.   Published online May 1, 2025
DOI: https://doi.org/10.4313/JKEM.2025.38.3.1
In parallel with the efforts to improve the device performance in modern integrated circuits, it is necessary to downscale their core components, field-effect transistors (FETs), generally gauged by their physical gate length. Upon such device scaling, the emergence of the short-channel effect impedes further scaling into the nanometer scale in the silicon VLSI (Very-Large-Scale-Integration) system. To address this issue, two-dimensional (2D) semiconductors, leveraging their atomically thin thickness and dangling-bond-free characteristics, are being highlighted as a material solution for future scaling technology without severe mobility degradation. Despite the expected ideal physical properties, 2D semiconductors have yet to realize their full potential owing to the limited development of integration technology. In this context, we survey and review the tailored van der Waals integration technologies for 2D FETs. In particular, we provide an in-depth study of both van der Waals integrated contact and dielectric methods along with an explanation of customized materials. In essence, this van der Waals integrationcentered approach will be a core strategy to implement the high-performance 2D transistors that meet the demand of FET miniaturization.
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Quantum Computing Revolutionizing Materials Science: Basic Principles and Trends in Applications for Nanomaterials
Jae-hee Han, Joonho Bae
J Electr Electron Mater 2024;37(6):590-599.   Published online November 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.6.3
Quantum computing is set to transform the field of materials science, offering computational methods that could far surpass conventional approaches for tackling intricate material design challenges. This review introduces the foundational principles of rapidly growing quantum computing and its application trends in the design and analysis of nanomaterials. We explain how quantum speedup, achieved through quantum algorithms utilizing qubit superposition and entanglement, is applied to material design. Additionally, the principles and research trends of quantum variational methods, including the Variational Quantum Eigensolver (VQE), which has recently gained attention as a quantum algorithm simulation technique, will be discussed. By combining new techniques based on quantum algorithms with the quantum speed-up, the quantum computing is expected to offer new insights into data-intensive materials research and provide innovative methodologies for the development of new functional materials. With the advancement of quantum algorithms, the field of materials science could enter a new era, enabling more precise and efficient approaches in materials design and functional analysis.
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Analysis of Operation Parameter Impact on Electrical Characteristics Activation in TiO2/TiO2-x Based Memristors
Beom Gu Lee, Jae-yun Lee, Jung Hun Choi, Jung Moo Seo, Sung-jin Kim
J Electr Electron Mater 2024;37(6):649-656.   Published online November 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.6.11
Memristors, as next-generation memory devices, have garnered significant academic interest. Among them, TiO2/TiO2-x based memristors have particularly attracted substantial scholarly attention. Research on the activation and stability of TiO2 based memristor devices through process parameters is essential. Here, to determine the impact of process parameters on the activation of TiO2/TiO2-x based memristor devices, we fabricated the memristor devices using a sputtering system andconducted annealing at 400℃. Additionally, to analyze the electrical characteristics of the devices, we measured the I-V curves and C-V curves. Also, we examined TiO2/TiO2-x based memristor devices surface using SEM. Consequently, it was observed that the devices subjected to annealing exhibited improved hysteresis curves in the I-V characteristics, a reduced bandgap, and changes in resistance compared to the non-annealed devices. The retention test results further demonstrated that the set/reset characteristics of the devices were stable, confirming their potential applicability as memory devices.
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Fabrication of Low-Cost Physically Unclonable Function (PUF) Chip Using Multiple Process Variables
Hong-seock Jee, Dol Sohn, Ju-won Yeon, Tae-hyun Kil, Hyo-jun Park, Eui-cheol Yun, Moon-kwon Lee, Jun-young Park
J Electr Electron Mater 2024;37(5):527-532.   Published online September 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.5.9
Physically Unclonable Functions (PUFs) provide a high level of security for private keys using unique physical characteristics of hardware. However, fabricating PUF chips requires numerous semiconductor processes, leading to high costs, which limits their applications. In this work, we introduce a low-cost manufacturing method for PUF security chips. First, surface roughening through wet-etching is utilized to create random variables. Additionally, physical vapor deposition is added to further enhance randomness. After PUF chip fabrication, both Hamming distance (HD) and Hamming weight (HW) are extracted and compared to verify the fabricated chip. It is confirmed that the PUF chip using two different multiple process variables demonstrates superior uniqueness and uniformity compared to the PUF security chip fabricated using only a single process variable.
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Correction Measures That Take Humidity into Account in Insulating Oil Test Measurement Results
Wansu Kim, Jae-pil Roh, Seock-gu Kang
J Electr Electron Mater 2024;37(5):541-546.   Published online September 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.5.11
Climate conditions, especially transport and storage, are a very important factor in the process of sampling and testing insulation oil in the field. The samples of insulating oil exposed to the atmosphere affect the dielectric strength, total acid number and moisture test value by oxygen and high humidity environment and may also affect the results according to the criteria specified in each test. Therefore, reliable test values for insulating oil testing require consideration of the atmospheric environment of the test site, including oxygen and humidity. In this paper, each test was conducted on insulating oil exposed to various time and humidity environments, and the effect of the atmospheric environment on the test results was analyzed by comparing and analyzing with the first insulating oil.
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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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Theoretical Insights into Oxygen Vacancies in Reduced Bulk TiO₂: A Mini Review
Jaehyuk Choi, Junho Lee, Taehun Lee
J Electr Electron Mater 2024;37(3):231-240.   Published online May 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.3.1
Titanium dioxide (TiO₂) holds significant scientific and technological relevance as a key photocatalyst and resistive random-access memory, demonstrating unique physicochemical properties and serving as an n-type semiconductor. Understanding the density and arrangement of oxygen vacancies (VOs) is crucial for tailoring TiO₂’s properties to diverse technological needs, driving increased interest in exploring oxygen vacancy complexes and superstructures. In this mini review, we summarize the recent understandings of the fundamental properties of oxygen vacancies in bulk rutile (R-TiO₂) and anatase (A-TiO₂) based on DFT and beyond method. We specifically focus on the excess electrons and their spatial arrangement of disordered single VO in bulk R and A-TiO₂, aligned with the experimental findings. We also highlight the theoretical works on investigating the geometries and stabilities of ordered VOs complexes in bulk TiO₂. This comprehensive review provides insights into the fundamental properties of excess electrons in reduced TiO₂, offering valuable perspectives for future research and technological advancements in TiO₂-based devices.
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Structural and Electrical Properties of (La0.7Sr0.3)(Mn1-xFex)O3 Thin Films Prepared by Sol-Gel Method for Thermistor Devices
Ji-su Yuk, Sam-haeng Yi, Myung-gyu Lee, Joo-seok Park, Young-gon Kim, Sung-gap Lee
J Electr Electron Mater 2024;37(2):164-168.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.6
(La0.7Sr0.3)(Mn1-xFex)O3 (LSMFO) (x = 0.03, 0.06, 0.09, 0.12) precursor solution are prepared by sol-gel method. LSMFO thin films are fabricated by the spin-coating method on Pt/Ti/SiO2/Si substrate, and the sintering temperature and time are 800℃ and 1 hr, respectively. The average thickness of the 6-times coated LSMFO films is about 181 to 190 nm and average grain size is about 18 to 20 nm. As the amount of Fe added in the LSMFO thin film increased, the resistivity decreased, and the TCR and B25/65-value increased. Electrical resistivity, TCR and B25/65-value of the (La0.7Sr0.3)(Mn0.88Fe0.12)O3 thin film are 0.0136 mΩ-cm, 0.358%/℃, and 328 K at room temperature, respectively. The resistivity properties of LSMFO thin films matched well with Mott’s VRH model.
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Electric-Field-Induced Strain Measurement of Ferroelectric Ceramics Using a Linear Variable Differential Transducer
Hyoung-su Han, Chang Won Ahn
J Electr Electron Mater 2024;37(2):141-147.   Published online March 1, 2024
DOI: https://doi.org/10.4313/JKEM.2024.37.2.3
The measurement of strain under an electric field has been widely employed to comprehend the fundamental principles of electro-mechanical responses in ferroelectric, piezoelectric, and electrostrictive materials. In particular, understanding the strain properties of piezoelectric materials in response to electrical stimulation is crucial for researching and developing components such as piezoelectric actuators, acoustic devices, and ultrasonic generators. This tutorial paper introduces the components and operational principles of the linear variable differential transducer (LVDT), a widely used displacement measurement device in various industries. Additionally, we present the configuration of an experimental setup using LVDT to measure the strain characteristics of ferroelectric, piezoelectric, or electrostrictive materials under the application of an electric field. This paper includes simple measurement results and analyses obtained through the LVDT experimental setup, providing valuable information on research methods for the electro-mechanical interactions of various materials.
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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 Electr Electron Mater 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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Recent Development of P-Tunnel Oxide Passivated Contact Solar Cells
Yang Zhao, Muhammad Quddamah Khokhar, Hasnain Yousuf, Xinyi Fan, Seungyong Han, Youngkuk Kim, Suresh Kumar Dhungel, Junsin Yi
J Electr Electron Mater 2023;36(4):332-340.   Published online July 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.4.3
Crystalline silicon solar cells have attracted great attention for their various advantages, such as the availability of raw materials, high-efficiency potential, and well-established processing sequence. Tunnel oxide passivated contact (TOPCon) solar cells are widely regarded as one of the most prospective candidates for the next generation of high-performance solar cells because an efficiency of 26% has been achieved in small-area solar cells. Compared to n-type TOPCon solar cells, the photo conversion efficiency (PCE) of p-type TOPCon is slightly higher. The highest PCEs of p-type TOPCon and n-type TOPCon solar cells are 26.0% and 25.8%, respectively. Despite the highest efficiency in small-area cells, limited progress has been achieved in p-type TOPCon solar cells for large are due to their lower carrier lifetime and inferior surface passivation with the boron-doped c-Si wafer. Nevertheless, it is of great importance to promoting the p-type TOPCon technology due to its lower price and well-established manufacturing procedures with slight modifications in the PERC solar cells production lines. The progress in different approaches to increase the efficiencies of p-type TOPCon solar cells has been reported in this review article and is expected to set valuable strategies to promote the passivation technology of p-type TOPCon, which could further increase the efficiency of TOPCon solar cells.
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Thermal Distribution Analysis of Triple-Stacked ZnO Varistor
Kyung-uk Jang
J Electr Electron Mater 2023;36(4):391-396.   Published online July 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.4.10
Recently, as power and electronic devices have increased in frequency and capacity, it has become a major concern to protect electronic circuits and electronic components used in these devices from abnormal voltages such as various surges and pulse noise. To respond to variously rated voltages applied to power electronic devices, the rated voltages of various varistors can be obtained by controlling the size of internal particles of the varistor or controlling the number of layers of the varistor. During bonding, the problem of unbalanced thermal runaway occurring between the electrode and the varistor interface causes degradation of the varistor and shortens its life of the varistor. In this study, to solve the problem of unbalanced heat distribution of stacked varistors to adjust the operating voltage, the contents of the ZnO-based varistor composition were 96 wt% ZnO, 1 mol% Sb2O3, 1 mol% Bi2O3, 0.5 mol% CoO, 0.5 mol% MnO, and 1 mol% TiO2. A multi-layered ZnO varistor was modeled by bonding a single varistor with a composition in three layers according to the operating voltage. The thermal distribution of the triple-layered ZnO varistor was analyzed for the thermal runaway phenomenon that occurred during varistor operation using the finite element method according to Comsol 5.2.
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Structural and Electrical Properties of (La0.7-xCex)Sr0.3MnO3 Ceramics
Tae-yeon In, Jeong-eun Lim, Byeong-jun Park, Sam-haeng Yi, Myung-gyu Lee, Joo-seok Park, Sung-gap Lee
J Electr Electron Mater 2023;36(3):249-254.   Published online May 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.3.6
La0.7-xCexSr0.3MnO3 specimens were fabricated by a solid state reaction method and structural and electrical properties with variation of Ce4+ contents were measured. All specimens exhibited a polycrystalline rhombohedral crystal structure, and the (110) peaks were shifted to low angle side with increasing the amount of Ce4+ contents. As Ce4+ ions with different ion radii and charges are substituted with La3+ ions, electrical properties are thought to be affected by changes in the double exchange interaction between Mn3+-Mn4+ ions due to distortion of the unit lattice, a decrease in oxygen vacancy concentration, and an increase in lattice defects. Resistivity gradually decrease as the amount of Ce4+ added increased, and negative temperature coefficient of resistance (NTCR) properties were shown in all specimens. In the La0.5Ce0.2Sr0.3MnO3 specimens, electrical resistivity, TCR and B-value were 31.8 Ω-cm, 0.55%/℃ and 605 K, respectively.
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How to Avoid Misinterpreting Experimental Data for Thermally Activated Processes
Ju-hyeon Lee, Jinsung Chun, Ku-tak Lee, Wook Jo
J Electr Electron Mater 2023;36(3):241-248.   Published online May 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.3.5
The value of experimentally obtained data becomes highest when they are properly analyzed based on valid logics. Many physical and chemical properties such as electrical and magnetic properties, chemical reaction rates, etc. are known to be thermally activated; thus, a proper understanding of thermally-activated processes is of importance. However, there are still a number of papers published with falsely analyzed data. In this contribution, we would like to revisit the meaning of thermally-activated processes, and then reanalyze a data set published misinterpreted. By showing a step-by-step procedure for the reanalysis, we would like to help researchers who may come across such data in the future not to make mistakes in their analysis.
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Structural and Electrical Properties of La0.7Sr0.3-xMgxMnO3 Ceramics with MgO Content
Hyun-tae Kim, Jeong-eun Lim, Byeong-jun Park, Sam-haeng Yi, Myung-gyu Lee, Joo-seok Park, Young-gon Kim, Sung-gap Lee
J Electr Electron Mater 2023;36(3):275-279.   Published online May 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.3.10
La0.7Sr0.3-xMgxMnO3 (LSMMO) (x=0.05~0.20) specimens are fabricated by a solid phase sintering method, and the sintering temperature and time are 1,300℃ and 2 hours, respectively. The dependence of the crystalline structure according to the amount of Mg2+ contents is not observed, and all specimens show a polycrystalline rhombohedral crystal structure, the X-ray diffraction (110) peaks move to the high angle side with increasing the amount of Mg2+ contents. LSMMO specimens exhibit a granule-shaped microstructure with an average grain size of 1 μm or less. Resistivity gradually decrease as the amount of Mg2+ contents increased. And in the La0.7Sr0.1Mg0.2MnO3 specimen, resistivity and B25/65-value are 36.7 Ω-cm and 394 K at room temperature, respectively. LSMMO specimens show a variable-range hopping (VRH) electrical conduction mechanism, and the negative temperature of coefficient of resistance (NTCR) is approximately 0.37~0.38%/℃.
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Electrochemical Catalysts Test for Nano Pt Particles on Carbon Support Synthesized by a Polyol Process Parameter Control
Chae Lin Moon, Jin Woo Bae, Soon Mok Choi
J Electr Electron Mater 2023;36(2):164-169.   Published online March 1, 2023
DOI: https://doi.org/10.4313/JKEM.2023.36.2.9
Nano Pt particles were dispersed on carbon-based supports by a polyol process for a catalyst application in a polymer electrolyte fuel cell. We tried to optimize the effect of pH on the electrostatic forces between the support and the Pt colloids. We investigated the relationship among the surface charges on the carbon support, the solution pH, and the concentration of a glycolate, and the Pt particle size. The produced catalyst with nano Pt particles on the support was evaluated by the long-term cyclic voltammetry (CV) performance test and compared with the results from a commercial catalyst. Our experimental results reveal that the pH-control can modify the particle size distribution and the dispersion of the nano Pt particles. This resulted in a cost-effective method for the synthesis of highly Pt loaded Pt/C catalysts for fuel cells better than a commercial catalyst system.
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Device Optimization for Suppression of Short-Channel Effects in Bulk FinFET with Vacuum Gate Spacer
Ji-yeong Yeon, Khwang-sun Lee, Sung-su Yoon, Ju-won Yeon, Hagyoul Bae, Jun-young Park
J Electr Electron Mater 2022;35(6):576-580.   Published online November 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.6.6
Semiconductor devices have evolved from 2D planar FETs to 3D bulk FinFETs, with aggressive device scaling. Bulk FinFETs make it possible to suppress short-channel effects. In addition, the use of low-k dielectric materials as a vacuum gate spacer have been suggested to improve the AC characteristics of the bulk FinFET. However, although the vacuum gate spacer is effective, correlation between the vacuum gate spacer and the short-channel-effects have not yet been compared or discussed. Using a 3D TCAD simulator, this paper demonstrates how to optimize bulk FinFETs including a vacuum gate spacer and to suppress short-channel effects.
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Creating Structure with Pymatgen Package and Application to the First-Principles Calculation
Dae-hyung Lee, Dong-hwa Seo
J Electr Electron Mater 2022;35(6):556-561.   Published online November 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.6.3
Computational material science as an application of Density Functional Theory (DFT) to the discipline of material science has emerged and applied to the research and development of energy materials and electronic materials such as semiconductor. However, there are a few difficulties, such as generating input files for various types of materials in both the same calculating condition and appropriate parameters, which is essential in comparing results of DFT calculation in the right way. In this tutorial status report, we will introduce how to create crystal structures and to prepare input files automatically for the Vienna Ab initio Simulation Package (VASP) and Gaussian, the most popular DFT calculation programs. We anticipate this tutorial makes DFT calculation easier for the ones who are not experts on DFT programs.
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진공인터럽터의 내전압 성능 향상을 위한 전류컨디셔닝 기법 연구
Young-kwang Cha, Il-hoi Lee, Ki-beom Jeon, Ji-hoon Jang, Heung-jin Ju
J Electr Electron Mater 2022;35(5):480-487.   Published online September 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.5.9
As a process to improve the insulation performance of VIs (Vacuum Interrupters), AC voltage conditioning is generally adopted by many manufacturers. Although the insulation performance is enhanced easily with AC Voltage conditioning, it has limitations when high recovery voltage is required due to high voltage rate or capacitive current switching. In particular, impurities such as oxides segregated on the electrode surface can be removed not by the energy level of the voltage conditioning but by the higher energy level achieved by the current conditioning process In this article, the current conditioning was carried out in various conditions and its validity was examined. The current conditioning was processed by changing the amplitude of applied current, arc time, the number of tests, and frequency. The insulation performance and the status of contact surface were checked as well. We concluded that as the applied charge quantity and the conditioning coverage area increase, the conditioning effect is much higher.
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Analysis of Thermal Runaway Phenomenon Caused by ZnO Varistor Operation Using Finite Element Method
Kyung-uk Jang
J Electr Electron Mater 2022;35(4):372-376.   Published online July 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.4.9
Since the ZnO varistor is a semiconductor device, the internal thermal distribution during the varistor operation is recognized as an important factor in the performance and deterioration of the varistor. For an optimal varistor structure design, the thermal runaway phenomenon during the varistor operation was interpreted using the Comsol 5.2 analysis program by a finite element analysis. The maximum temperature of the center measured in the cross section of the ZnO varistor was confirmed to increase as the temperature moved from the lower electrode to the center towards the upper electrode up to 572.6 K. The electrodes are thinned so that the influence of the Schottky barrier is not great. The heat gradient balance is determined to be improved when the electrode of the hybrid form is introduced. The thickness, density, pore distribution, impurity uniformity, and particle size of the ZnO varistor are required, and it is determined that the pyrolysis gradient will be improved regardless of the electrode thickness. When these results are applied to design the ZnO varistor, the optimal structure of the ZnO varistor can be obtained.
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Development of Variable Vacuum Capacitor with Maximum Voltage of 12 kV and Capacitance of 50 to 500 pF
Youngkwang Cha, Ilhoi Lee, Kibeom Jeon, Jihoon Jang, Heungjin Ju, Seungkil Choi
J Electr Electron Mater 2022;35(3):232-240.   Published online May 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.3.4
A variable vacuum capacitor (VVC), which is a variable element, is used to match impedance in plasma that changes with various impedance values, and its use is expanding with the rapid growth of the semiconductor business. Since VVCs have to secure insulation performance and vary capacitance within a compact size, electrode design and manufacturing are very important; thus, various technologies such as part design and manufacturing technology and vacuum brazing technology are required. In this study, based on the model of an advanced foreign company that is widely used for impedance matching in the manufacture of semiconductors and displays, a VVC that can realize the same performance was developed. The electrode part was designed, the consistency was confirmed through analysis, and the precision of capacitance was improved by designing a cup-type electrode to secure the concentricity of the electrode. As a result of the evaluation, all requirements was satisfied. We believe that self-development will be possible if satisfactory responses are received through evaluation by VVC consumers in the future.
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Optimizing Lamination Process for High-Power Shingled Photovoltaic Module
Jeongho Jeong, Hongsub Jee, Junghoon Kim, Wonyong Choi, Chaehwan Jeong, Jaehyeong Lee
J Electr Electron Mater 2022;35(3):281-291.   Published online May 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.3.11
Global warming is accelerating due to the use of fossil fuels that have been used continuously for centuries. Now, humankind recognizes its seriousness, and is conducting research on searching for eco-friendly and sustainable energy. In the field of solar energy, which is a kind of eco-friendly and sustainable, many studies are being conducted to enhance the output performance of the module. In this study, the output improvement for the shingled module structure was studied. In order to improve the output performance of the module, the thickness of the encapsulant was increased, and the lamination process conditions have been improved accordingly. After that, the crosslinking rate was analyzed, and the suitability of the lamination process conditions was judged using this. In addition, a peeling test was conducted to analyze the correlation between the adhesion of the encapsulant and the output performance of the module. Finally, the optimization for the encapsulant material and the lamination process conditions for high-power shingled modules was established, and accordingly, the market share of high-power shingled modules in the solar module market can be expected to rise.
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Design and Fabrication of SiO2/TiO2 Multi Layer Thin Films on Silicon Encapsulation of LED Deposited by E-beam Evaporation for NIR Narrow Band Pass Filter Application
Dong Pyo Kim, Kyung-seob Kim, Goo-cheol Kim, Jung-chae Jeong
J Electr Electron Mater 2022;35(2):165-171.   Published online March 1, 2022
DOI: https://doi.org/10.4313/JKEM.2022.35.2.9
The SiO2/TiO2 multilayer thin films used for narrow band pass filter were fabricated using E-beam evaporation method. The narrow band pass filter was used to enhance the resolution of spectroscopy and sensor applications with near infrared (NIR) light source. The narrow band pass filter with multilayer thin films were designed with Essential Macleod program. The multilayers of SiO2/TiO2 with 32 layers were deposited on the silicon encapsulation of IR with peak wavelength (λp) of 660 nm and NIR LEDs with λp of 830 nm, 880 nm, and 955 nm. After NIR light passed through the narrow band pass filter, the full width of half maximum of 33.4~48.6 nm became narrow to 20~24 nm owing to the absorption of photons with short or long wavelength of designed band of 20 nm. The SiO2/TiO2 band pass filter fabricated in this study can be used for sensor, optoelectronics, and NIR spectroscopy applications.
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Thermal Analysis Characteristics of Vacuum Interrupter for Load Switcher
Kyunguk Jang
J Electr Electron Mater 2021;34(3):209-213.   Published online May 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.3.8
The 22.9 kV vacuum interrupter (VI) built-in load bus switcher (LBS), which is most often used as a load switch for distribution, extinguishes the arc that occurs during normal load opening and closing and fault current interruption within the VI housing to quickly switch circuits. As a protective device for contact separation, the rated current is supplied in a normal state. When a fault current flows due to a fault or an accident in the power system, the contact is disconnected in a vacuum state to block the fault current. In this study, in order to design the optimal VI, the heat dissipation characteristics of VI according to the center electrode distance 0/1/2/3 cm were analyzed by applying the finite element method, and the results were reflected to improve the structure of the VI.
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Electrical Properties of CNT/Al/Cu Composite Fiber Deposited by Thermal Vacuum Evaporation
Jong-seok Kim, Paik-kyun Shin
J Electr Electron Mater 2021;34(2):105-109.   Published online March 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.2.4
CNT fiber has been in the spotlight as a conductor, but the conductivity of CNT fibers do not match that of CNT. This study reveals that the conductivity of CNT fiber can be improved by depositing Al/Cu through vacuum evaporation. Cu is commonly used for deposition on CNT fibers. But low bonding strength of the interface between CNT and Cu could be a disadvantage. To overcome this, Al was deposited on the CNT fiber for forming aluminum carbide islands to increase the interfacial bonding strength. The conductivity characteristics were improved as the deposition time increased. The resistance was measured as a function of temperature, demonstrating that the temperature coefficient of resistance (TCR) is improved to be 241 ppm/℃ in comparison with that of as-received CNT fibers at -1,251 ppm/℃, when the CNT fibers are deposited with Al and Cu, respectively, for 90s and for 540s.
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Effects of Plasma Treatment on the Reliability of a-IGZO TFT
Dongxu Xin, Ziyang Cui, Taeyong Kim, Junsin Yi
J Electr Electron Mater 2021;34(2):85-89.   Published online March 1, 2021
DOI: https://doi.org/10.4313/JKEM.2021.34.2.1
High reliability thin film transistors are important factors for next-generation displays. The reliability of transparent a-IGZO semiconductors is being actively studied for display applications. A plasma treatment can fill the oxygen vacancies in the channel layer and the channel layer/insulating layer interface so that the device can work stably under a bias voltage. This paper studies the effect of plasma treatment on the performance of a-IGZO TFT devices. The influence of different plasma gases on the electrical parameters of device and its working reliability are reviewed. The article mentions argon, fluorine, hydrogen and several ways of processing in the atmosphere. Among these methods, F (fluorine) plasma treatment can maximize equipment reliability. It is expected that the presented results will form a basis for further research to improve the reliability of a-IGZO TFT.
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