Wearable temperature sensors are becoming increasingly important for continuous health monitoring, personalized healthcare, and biointegrated electronic systems. However, conventional temperature-sensing platforms often suffer from limited thermal sensitivity, insufficient mechanical compliance, and unstable performance under repeated deformation, making it difficult to detect subtle physiological temperature variations in real time. Here, this tutorial status report presents a fabrication strategy for highly sensitive wearable temperature sensors based on gold-doped crystalline silicon nanomembranes. Gold diffusion into crystalline silicon introduces deep-level impurity states that modulate the Fermi level and shift the freeze-out region toward the physiological temperature range, enabling an ultrahigh negative temperature coefficient of resistance. By integrating the gold-doped silicon nanomembrane with a polyimide-supported ultrathin platform, neutral mechanical plane design, and serpentine mesh interconnects, the resulting device can provide high thermal sensitivity, fast response, conformal skin attachment, and stable operation under mechanical deformation. This fabrication approach is expected to broaden the use of impurity-engineered silicon nanomembranes in next-generation wearable sensors, flexible bioelectronics, and multifunctional healthcare monitoring systems.

Lead-free bismuth sodium titanate (BNT)-based ceramics have attracted strong attention as environmentally benign dielectric materials for high-efficiency electrostatic energy-storage capacitors. A key challenge is that pristine BNT typically exhibits large hysteresis, high remnant polarization, and limited dielectric reliability, which restrict recoverable energy storage and efficiency under practical electric fields. Here, we present a focused mini-review of recent studies to clarify how composition design, phase boundary tuning, defect chemistry, and microstructural control collectively enable slim or pinched polarization-electric field (P-E) behavior and improved energy-storage functionality in BNT-related bulk ceramics. The reviewed outcomes consistently show that stabilizing relaxor states governed by polar nanoregions (PNRs), often via solid-solution engineering and secondary relaxor/antiferroelectric-like incorporation, suppresses irreversible switching and reduces hysteresis loss, while densification and grain-size control enhance electrical homogeneity and breakdown strength. In addition, defect-mediated tuning of oxygen vacancy-related complexes is highlighted as an independent lever to control relaxor ergodicity and polarization reversibility, providing a complementary route to slim-loop optimization. These insights are expected to guide integrated design strategies that couple phase/relaxor-state engineering with defect and microstructure optimization, accelerating the development of reliable, temperature-robust, lead-free dielectric capacitors based on BNT-related ceramics.

The potential of replacing crosslinked polyethylene (XLPE) with an eco-friendly alternative, polypropylene (PP), as insulating material is investigated for overhead power distribution lines. Although XLPE exhibits excellent electrical and mechanical properties, the byproducts generated during crosslinking pose environmental challenges. PP is a viable alternative because of recyclability and absence of byproducts during crosslinking. This study evaluated alternating current (AC) breakdown strength, contact angle, and tracking resistance of two commercially available XLPE samples and three types of PP (PP1, PP2, PP3) with varying additive content. AC breakdown strength, analyzed using the Weibull distribution, facilitated relative comparison of insulation performance. PP2 exhibited scale parameters comparable to or exceeding those of XLPE. Contact angles exceeding 90° displayed hydrophobicity across all samples. To address pass/fail evaluation limitations, arcing images from tracking tests were analyzed using the box-counting method for fractal dimension analysis. Fractal dimensions increased with arcing extent, and complexity increased with test duration. Tracking resistance performance order was PP3, PP1, CC, PP2, OC which was attributed to enhanced heat dissipation properties of filler additives. The proposed quantitative method for comparing tracking resistance through fractal dimension analysis, explored the feasibility of using PP insulating materials in overhead power distribution lines.

The rapid proliferation of artificial intelligence (AI) servers and high-performance computing systems has significantly elevated the technical and reliability requirements for multilayer ceramic capacitors (MLCCs). In such systems, MLCCs are critical passive components that must deliver high capacitance, fast transient response, and robust insulation performance under high temperature, voltage, and current density. This review examines the material, structural, and process innovations that underpin MLCC performance in AI applications. Key topics include the development of ultrathin dielectric layers (<0.5 μm), rare-earth doped BaTiO₃-based dielectrics with enhanced DC bias stability, and core-shell microstructures designed for temperature and field resilience. The paper also explores insulation degradation mechanisms―such as vacancydriven conduction and demixing―and advanced reliability assessment methodologies, including HALT, TSDC, and the tipping point framework. Comparisons with automotive-grade MLCCs highlight the unique requirements of AI systems, such as ultraminiaturization, high volumetric efficiency, and ppm-level field failure rates. Finally, the review discusses emerging trends in MLCC technology, including particle engineering, interface stabilization, and advanced lamination techniques, and provides insight into the future direction of capacitor development tailored to AI data center environments.

Silicon carbide (SiC) power devices are attracting increasing attention for high-voltage and high-efficiency applications due to their superior material properties. However, achieving an optimal trade-off between specific on-resistance (Ron,sp) and breakdown voltage (BV) remains a key design challenge in planar MOSFET structures. In this study, twodimensional TCAD simulations were conducted to investigate the impact of varying the doping concentrations of the P-well (from 3 × 10¹⁷ to 6 × 10¹⁷ cm^-3) and JFET regions (from 1 × 10¹⁶ to 7 × 1016 cm^-3) on the electrical characteristics of 2.4 kVclass planar SiC MOSFETs. To maintain comparable BV conditions for 2.4 kV operation, two groups with P-well doping concentrations of 4.5 × 10¹⁷ cm^-3 and 5.3 × 1017 cm^-3 were analyzed and compared. When the P-well and JFET doping concentrations were 4.5 × 10¹⁷ cm^-3 and 1.5 × 10¹⁶ cm^-3, respectively, the simulated Ron,sp and BV were 1.41 mΩ·cm² and 3,150 V. In contrast, with P-well and JFET doping concentrations of 5.3 × 10¹⁷ cm^-3 and 5.0 × 10¹⁶ cm^-3, the Ron,sp was reduced to 1.31 mΩ·cm² while the BV slightly increased to 3,200 V. Based on these results, an optimized device structure was proposed, demonstrating its potential for integration into high-voltage SiC-based power systems. This study provides practical design insights and is expected to contribute to the advancement of wide bandgap semiconductor technologies for next-generation power electronics.

Quantum dots (QDs) offer size-dependent tunability across the infrared to ultraviolet range with narrow emission linewidths and high color purity, making them highly attractive for next-generation light-emitting devices. Quantum dot lightemitting diodes (QLEDs) further combine precise spectral control with scalable, low-cost solution processing, positioning them as strong candidates for wearable, stretchable, and AR/VR display technologies. However, conventional single-emission QLEDs suffer from charge imbalance, efficiency roll-off, and limited operational lifetime, necessitating new device architectures. Tandem QLEDs, which vertically stack multiple emissive layers (EMLs) connected by charge generation layers (CGLs), provide a compelling solution by enabling higher luminance, improved charge balance, and longer lifetime at equivalent current density. The CGL serves as the interfacial region mediating charge injection and generation between adjacent EMLs, directly determining device efficiency and stability. This review highlights recent progress in CGL engineering, categorizing representative designs into planar heterojunction, inorganic-based, and dipole-based configurations. Comparative analysis of their formation mechanisms, material systems, and process compatibilities reveals evolving charge-control strategies that extend beyond material selection. These insights establish design principles for next-generation tandem QLEDs with enhanced efficiency, durability, and manufacturability.

This study investigates the insulation performance of a 66 kV dry-type submarine cable used in offshore wind farms under mechanical aging. During installation and operation, submarine cables are subjected to various mechanical stresses, including tension, compression, and bending, which can lead to insulation deterioration. In this study, XLPE samples extracted from a submarine cable were prepared and subjected to controlled tensile strain below the yield strain to evaluate their mechanical and electrical performance. Changes in tensile strength, elongation, and tan δ (dielectric loss factor) were measured to assess the extent of aging. The results indicate that as the applied strain and exposure duration increased, tensile strength and elongation decreased, while tan δ values increased, signifying a decline in electrical insulation performance. A strong negative correlation (R = -0.809) was observed between tan δ and tensile strength, demonstrating that mechanical aging significantly affects electrical properties. These findings highlight the importance of minimizing excessive mechanical stress during the installation and operation of submarine cables. The results provide valuable insights for enhancing the reliability of submarine cables in offshore wind farms and emphasize the necessity of optimized design and maintenance strategies to mitigate the effects of mechanical aging.

This study developed a dielectric composition for high-capacitance MLCCs with C0G and U2J temperature compensation characteristics (Class I) under reducing conditions. The potential application of this composition in highpermittivity class I MLCCs was examined. Using (Ba₀.₂₄Ca₀.₁₆Sr₀.₆)(TiₓZr₁₋ₓ)O₃. XRD analysis showed that secondary phases like Sr₂TiO₄ and TiO₂ formed at higher Ti content, affecting the stoichiometric balance. Adjusting the Ti/Zr molar ratio resulted in a dielectric constant of 41.2 ~ 105, a dielectric loss of 0.082 ~ 0.174%, and insulation resistance above 1.6 × 10¹³ ohms at 25℃. The TCC shifted from C0G to U2J as the Ti/Zr ratio increased, but the composition enabled the design of high-capacitance and high-voltage MLCCs with favorable dielectric and electrical properties.

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.

The search for sustainable and efficient energy conversion technologies is becoming increasingly critical in response to global energy and environmental challenges. Traditional lead-based piezoelectric materials, such as lead zirconate titanate (PZT), have high piezoelectric constant but present significant health problems and environmental risks due to their hazardous metal contaminants. This study addresses these concerns by investigating barium titanate (BTO), a lead-free alternative, and enhancing its performance using anisotropic nanowires (NWs) structures. BTO NWs were synthesized via a two-step hydrothermal method and incorporated into a poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] matrix to fabricate a piezoelectric composite film. The resulting device demonstrated a notable increase in electrical output compared to devices based on isotropic morphology of BTO nanoparticles, exhibiting enhanced performance. These findings suggest that BTO NWs hold significant promise for applications in flexible and wearable electronics, paving the way for further advancements in sustainable energy technology.

The display industry has recently been at the forefront of innovative advancements in modern electronic devices. Technological progress such as flexible display holds significant potential across various application fields, particularly in wearable devices and rollable displays. A low-temperature process is essential for fabricating such displays. One of the key technologies in displays is the thin film transistor (TFT), with amorphous indium gallium zinc oxide (a-IGZO) receiving particular attention. a-IGZO is widely applied in high-performance displays due to its high charge mobility and stability. While a thermal treatment above 350℃ is typically required to maximize the electrical performance of a-IGZO TFTs, such high temperatures pose challenges for utilizing polymer substrates like plastics. Here, we thesis investigates the simultaneous lowtemperature plasma annealing process to develop next-generation high-performance flexible display devices. To define the optimal temperature, devices were fabricated and analyzed at varying temperatures of 40℃, 80℃, 120℃, and 160℃. Experimental results indicated that devices fabricated at 160℃ and 80℃ exhibited superior performance, with those at 160℃ demonstrating better performance in terms of current ratio, threshold voltage, and subthreshold swing. These findings confirm that the simultaneous low-temperature plasma annealing process is effective for next-generation high-performance displays.

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.

In this study, the electrical properties of a C0G (class 1 ceramic) dielectric composition with internal reducibility, specifically (Ba_0.27CaSr)(Zr_0.95Ti_0.05)O₃, were investigated by fixing Ba at the A site and varying the Ca/Sr molar ratio. The potential application of this composition in high-permittivity C0G MLCCs was examined. The powder was calcined at 1,150℃ for 2 hours, as determined by TG-DTA analysis, and the resulting powder was ground to achieve a particle size (D50) of 0.35 to 0.4 μm and a specific surface area (BET) of 4.5 to 5.0 g/m². With a Ca/Sr molar ratio of 0.3, the composition (Ba0.27Ca0.17Sr0.56) (Zr0.95Ti0.05)O₃ exhibited electrical properties with a permittivity of 41.9, a loss of less than 0.008%, and an insulation resistance exceeding 2.2×10¹³ Ω. The feasibility of using this composition for high-capacitance C0G MLCCs was confirmed.

Titanium oxide (TiO₂), a representative photocatalyst, reacts to ultraviolet ray energy and has antibacterial, deodorizing, and antifouling properties using superhydrophilic properties, so it is widely used in various industrial fields such as environmental purification, building exterior walls, and road facilities. However, due to the nature of the photocatalyst, it reacts to ultraviolet rays known to be harmful to the human body, and is designed to react to natural light outdoors and to ultraviolet light sources inside a sealed device indoors, so indoor space is extremely limited. This study aims to develop spatial antibacterial technology for everyday living spaces by researching methods for antibacterial and deodorization by reacting titanium oxide (TiO₂)-based photocatalysts with the visible light range emitted from lighting devices in everyday spaces. Through the results of this study, it was verified through experiments that the photocatalyst exhibits antibacterial and deodorizing properties in response to lighting devices (LED, fluorescent lights, etc.) used in daily life. Based on the research results, we hope that various studies will be conducted to create a safer living environment by applying this technology to various fields such as large-scale complex facilities where an unspecified number of floating populations gather, airports, port waiting rooms, and public transportation.

This research explores the development of [100]-textured barium titanate (BaTiO₃, BT) ceramics using sodium bismuth titanate (Na_0.5Bi_4.5Ti₄O₁₅, NBiT) templates, aimed at leveraging the inherent high dielectric property of BT. However, the attempted texturing was unsuccessful, primarily due to bismuth diffusion from the NBiT templates into the BT matrix below the sintering temperature, at 1,000℃. Systematical exploration about the cause of the failure is involved and alternative approaches are proposed in detail to overcome the challenge. These findings contribute to the understanding of techniques and conditions for textured ceramic fabrication and highlight the need for further research in this area.

The low-temperature coefficient of resistance (TCR) is a crucial factor in the development of space-grade resistors for temperature stability. Consequently, extensive research is underway to achieve zero TCR. In this study, resistors were deposited by co-sputtering nickel-chromium-based composite compositions, metals showing positive TCR, with SiO₂, introducing negative TCR components. It was observed that achieving zero TCR is feasible by adjusting the proportion of negative TCR components in the deposited thin film resistors within certain compositions. Additionally, the correlation between TCR and deposition conditions, such as sputtering power, Ar pressure, and surface roughness, was investigated. We anticipate that these findings will contribute to the study of resistors with very low TCR, thereby enhancing the reliability of space-level resistors operating under high temperatures.

This reports the electrical properties of single-crystal β-gallium oxide (β-Ga₂O₃) vertical Schottky barrier diodes (SBDs) with a different guard ring structure. The vertical Schottky barrier diodes (V-SBDs) were fabricated with two types guard ring structures, one is with metal deposited on the Al₂O₃ passivation layer (film guard ring: FGR) and the other is with vias formed in the Al₂O₃ passivation layer to allow the metal to contact the Ga₂O₃ surface (metal guard ring: MGR). The forward current values of FGR and MGR V-SBD are 955 mA and 666 mA at 9 V, respectively, and the specific on-resistance (Ron,sp) is 5.9 mΩ·cm² and 29 mΩ·cm². The series resistance (Rs) in the nonlinear section extracted using Cheung’s formula was 6 Ω, 4.8 Ω for FGR V-SBD, 10.7 Ω, 6.7 Ω for MGR V-SBD, respectively, and the breakdown voltage was 528 V for FGR V-SBD and 358 V for MGR V-SBD. Degradation of electrical characteristics of the MGR V-SBD can be attributed to the increased reverse leakage current caused by the guard ring structure, and it is expected that the electrical performance can be improved by preventing premature leakage current when an appropriate reverse voltage is applied to the guard ring area. On the other hand, FGR V-SBD shows overall better electrical properties than MGR V-SBD because Al₂O₃ was widely deposited on the Ga₂O₃ surface, which prevent leakage current on the Ga₂O₃ surface.

Recently, as interest in personal hygiene has increased due to the community spread of COVID-19 and variant viruses, fixed and potable UV germicidal equipment to sterilize indoor spaces and hand-held UV germicidal equipment to sterilize household items such as masks and mobile phones are continuously being developed and sold. However, the development and sales of the product are difficult because appropriate testing methods have not yet been established. In this situation, if an uncertified product is distributed in the market, it can cause serious harm to consumers. In this study, we investigate the photobiological risks and safety devices against UV exposure of UV germicidal equipment distributed domestically, and propose appropriate test methods for portable UV germicidal equipment based on the research results.

To evaluate the possibility as a multi-level memory medium for the Ge2Sb2Te5/TiN/W-doped Ge2Sb2Te5 cell structure, the crystallization rate and stabilization characteristics according to voltage (V)- and current (I)- pulse sweeping were investigated. In the cell structures prepared by a magnetron sputtering system on a p-type Si (100) substrate, the Ge2Sb2Te5 and W-doped Ge2Sb2Te5 thin films were separated by a barrier metal, TiN, and the individual thicknesses were varied, but the total thickness was fixed at 200 nm. All cell structures exhibited relatively stable multi-level states of high-middle-low resistance (HR-MR-LR), which guarantee the reliability of the multilevel phase-change random access memory (PRAM). The amorphousto- multilevel crystallization rate was evaluated from a graph of resistance (R) vs. pulse duration (T) obtained by the nanoscaled pulse sweeping at a fixed applied voltage (12 V). For all structures, the phase-change rates of HR→MR and MR→LR were estimated to be approximately t<20 ns and t<40 ns, respectively, and the states were relatively stable. We believe that the doublestack structure of an appropriate Ge-Sb-Te film separated by barrier metal (TiN) can be optimized for high-speed and stable multilevel PRAM.

The effects of the annealing temperature on the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films grown on quartz substrates by radio-frequency magnetron sputtering were investigated. The thin films were annealed at various annealing temperatures for 20 min in a rapid thermal annealer after growing the thin films. The experimental results showed that the annealing temperature has a significant effect on the properties of the SrWO₄:Sm³⁺ thin films. The crystal structure of the as-grown SrWO₄:Sm³⁺ thin films was transformed from amorphous to crystalline after annealing at 800℃. The preferred orientation along (112) plane and a significant increase in average grain size by 820 nm were observed with increasing the annealing temperature. The average optical transmittance in the wavelength range of 500~1,100 nm was decreased from 72.0% at 800℃ to 44.2% at an annealing temperature of 1,000℃, where the highest value in the photoluminescence intensity was obtained. In addition to the red-shift of absorption edge, a higher annealing temperature caused the optical band gap energy of the SrWO₄:Sm³⁺ thin films to fall rapidly. These results suggest that the structural, morphological, and luminescent properties of SrWO4:Sm3+ thin films can be controlled by varying annealing temperature.

Tandem or multijunction solar cells (MJSCs) can convert sunlight into electricity with higher efficiency (η) than single junction solar cells (SJSCs) by dividing the solar irradiance over sub-cells having distinct bandgaps. The efficiencies of various common SJSC materials are close to the edge of their theoretical efficiency and hence there is a tremendous growing interest in utilizing the tandem/multijunction technique. Recently, III-V materials integration on a silicon substrate has been broadly investigated in the development of III-V on Si tandem solar cells. Numerous growth techniques such as heteroepitaxial growth, wafer bonding, and mechanical stacking are crucial for better understanding of high-quality III-V epitaxial layers on Si. As the choice of growth method and substrate selection can significantly impact the quality and performance of the resulting tandem cell and the terminal configuration exhibit a vital role in the overall proficiency. Parallel and Series-connected configurations have been studied, each with its advantage and disadvantages depending on the application and cell configuration. The optimization of both growth mechanisms and terminal configurations is necessary to further improve efficiency and lessen the cost of III-V on Si tandem solar cells. In this review article, we present an overview of the growth mechanisms and terminal configurations with the areas of research that are crucial for the commercialization of III-V on Si tandem solar cells.

In this paper, the 1,700 V level SiC-based power MOSFET device widely used in electric vehicles and new energy industries was designed, that is, a single trench gate power MOSFET structure and a double trench gate power MOSFET structure were proposed to analyze electrical characteristics while changing the design and process parameters. As a result of comparing and analyzing the two structures, it can be seen that the double trench gate structure shows quite excellent characteristics according to the concentration of the drift layer, and the breakdown voltage characteristics according to the depth of the drift layer also show excellent characteristics of 200 V or more. Among them, the trench gate power MOSFET device can be applied not only to the 1,700 V class but also to a voltage range above it, and it is believed that it can replace all Si devices currently applied to electric vehicles and new energy industries.

The purpose of this paper is to help those who research and develop solar cells in university laboratories and industrial sites understand the most basic and important quantum efficiency measurement and analysis method in analyzing solar cell performance. Starting with the definition of quantum efficiency, we calculate the theoretical current density according to the band gap of the solar cell material from the solar spectrum, along with a detailed introduction to the measurement and analysis methods, and measure and analyze the theoretical current density and quantum efficiency. We discuss in depth how to analyze the performance of solar cells through Quantum efficiency measurement and analysis of solar cells is a very useful method that can give intuition to solar cell performance analysis as it can analyze solar cells according to depth (front emitter, bulk, rear surface). Students and researchers who study solar cells with a deep understanding of theoretical current density and quantum efficiency measurement analysis are expected to use it as a basis for analyzing solar cell performance.

La_0.7Sr_0.3-xMg_xMnO₃ (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 La_0.7Sr_0.1Mg_0.2MnO₃ specimen, resistivity and B_25/65-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%/℃.

An analytical threshold voltage model is presented to observe the change in threshold voltage shift ΔV_th of a junctionless double gate MOSFET using ferroelectric-metal-SiO₂ as a gate oxide film. The negative capacitance transistors using ferroelectric have the characteristics of increasing on-current and lowering off-current. The change in the threshold voltage of the transistor affects the power dissipation. Therefore, the change in the threshold voltage as a function of theferroelectric thickness is analyzed. The presented threshold voltage model is in a good agreement with the results of TCAD. As a results of our analysis using this analytical threshold voltage model, the change in the threshold voltage with respect to the change in the ferroelectric thickness showed that the threshold voltage increased with the increase of the absolute value of charges in the employed ferroelectric. This suggests that it is possible to obtain an optimum ferroelectric thickness at which the threshold voltage shift becomes 0 V by the voltage across the ferroelectric even when the channel length is reduced. It was also found that the ferroelectric thickness increased as the silicon thickness increased when the channel length was less than 30 nm, but the ferroelectric thickness decreased as the silicon thickness increased when the channel length was 30 nm or more in order to satisfy ΔV_th=0.

In order to widely disseminate LED lighting, LED lighting technology that directly uses AC commercial power has been recently introduced. AC powered LED lighting technology has a problem in that the light brightness of the LED changes because the voltage applied to the LED and the current flowing through the LED continuously change. In this study, when the LED current is greater than the design current, the current control signal generated by the controller is supplied to the current source to supply only the design current to the LED by increasing the voltage drop at the current source. If it is smaller than the design current, the controller is adjusted so that the current is supplied only to the LED without a voltage drop in the current source. It can be seen that the higher the maximum rectified voltage, the faster the lighting time of the LED light emitting block is, so that the power factor of the LED lighting is improved. The LED lighting technology proposed in this study enables LED lighting with constant light brightness, reduced power consumption, and long lifetime.

We investigated the microstructure, crystal structure, dielectric, and elecromechanical strain properties of lead-free BaTiO₃ (BT)-modified (Bi_1/2Na_1/2)TiO₃-SrTiO₃ (BNT-ST) piezoelectric ceramics. Samples were prepared by a conventional ceramic processing route. Temperature dependent dielectric properties confirmed that a phase transition from a nonergodic relaxor to an ergodic relaxor was induced when the BT concentration reached 1.5 mol%, interestingly, where the average grain size reached a maximum value of 4.5 μm. At the same time, enhanced electromechanical strain (S_max/E_max = 600 pm/V) was obtained. It is suggested that the induced ferroelectric-relaxor phase transition by the BT modification is responsible for the enhancement of electromechanical strain in 1.5 mol% BT-modified BNT-ST ceramics.

In this study, SiO₂ 20 phr, ATH 70 phr, and platinum flame retardant were mixed with raw silicone rubber and -10 kV was applied to measure electrostatic charge attenuation voltage, surface resistance, and volume resistance, and the following conclusions were obtained. When the platinum flame retardant was 0 phr, the humidity 74.6% and the temperature was 21.8℃, the potential was half-reduced to 0.63 kV, 0.57 kV, and 0.44 kV when the applied voltage was changed from -10 kV to -8 kV, and the time halved to 50% was increased to 2.40 seconds, 2.47 seconds, and 2.61 seconds. It was confirmed that as the platinum flame retardant increased from 0.1 to 0.3 phr, the potential half-reduced to 0.67 kV, 0.60 kV, and 0.595 kV decreased, and the charge potential attenuation time half-reduced to 50% decreased to 3.44 seconds, 1.78 seconds, and 1.60 seconds. It was confirmed that the surface resistance increased as the humidity decreased, and the volume resistance decreased as the platinum flame retardant increased.

Bulk-sized PbTiO₃ (PT), which is widely known as a high-performance ferroelectric oxide but cannot be fabricated into a monolithic ceramic due to its high c/a ratio, was successfully prepared with a high tetragonality by partially substituting Ni ions for Pb ions using a solid-state reaction method. We found that Ni-doped PT was well-fabricated as a bulk monolith with a significant c/a ratio of ~1.06. X-ray diffraction on as-sintered and crushed samples revealed that NiTiO₃ secondary phase was present at the doping level of more than 2 at.%. Scanning electron microscopic study showed that NiTiO₃ secondary phase grew on the surface of PT specimens regardless of the doping level possibly due to the evaporation of Pb during sintering. We demonstrated that an unconventional introduction of Ni ions into A-site plays a key role on the fabrication of bulk PT, though how Ni ion functions should be studied further. We expect that this study contributes to a further development of displacive ferroelectric oxides with a high c/a ratio.

In order to increase the electrochemical performance of thermal battery anode, LIFT anode having the same weight but a larger lithium content in electrodes was fabricated by mixing lithium, iron and titanium. By applying these electrodes, a single cell and a thermal battery were prepared, and the effect of LIFT anode on electrochemical performance was evaluated. The LIFT-applied single cell presented a better cell performance than LIFe-applied single cell at 500℃ and 550℃. The discharge performance of LIFT-applied single cell, which included the operating time (787s), specific capacity (1,683 Asg^-1), and electrode utilization (80.7%), was improved collectively compared to the LIFe applied single cell (736s, 1,245 As g^-1, and 74.6%) at 500℃. As the discharge progressed, the internal resistance of LIFT anode decreased, because the lithium migration path was formed due to the presence of large titanium particles among iron particles. These results were analyzed in terms of the microstructure of electrode using SEM. Energy density of LIFT-applied single cell also increased by 10% to 142.1 Wh kg^-1 compared to that of LIFe-applied single cell (127.4 Wh kg^-1). In addition, the LIFT-applied single cell presented a stable discharge performance for 6,500s without a short circuit which could occur by molten lithium under an open circuit voltage condition with a high pressure (4 kgf cm^-2). As observed in the high temperature thermal battery performance tests, the voltage and specific capacity of LIFTapplied thermal battery are superior to those of LIFe-applied thermal batteries, indicating that the energy density of LIFT-applied thermal batteries should remarkably increase.