The ability to manipulate and probe biomolecules at the single-molecule level has become an essential approach for understanding molecular interactions, conformational dynamics, and nanoscale transport phenomena. Advances in experimental techniques have enabled precise control of individual molecules with high spatial resolution and piconewton-level force sensitivity. These developments have significantly expanded the capability of studying biomolecular mechanics and dynamics beyond conventional ensemble measurements. A variety of physical strategies have been developed for single-molecule manipulation, including mechanical-force-based approaches, electric-field-driven methods, and nanoscale structural confinement techniques. Mechanical-force-based methods, such as optical tweezers, magnetic tweezers, and atomic force microscopy, enable direct measurement of molecular mechanical responses. Electric-field-based manipulation, represented by dielectrophoresis, allows noncontact control of particles and biomolecules through polarization effects in non-uniform electric fields. In addition, nanopore-based systems employ nanoscale confinement to regulate molecular transport and residence behavior. This review provides an overview of representative single-molecule manipulation techniques based on mechanical, electrical, and structural control and discusses their fundamental principles and implementation strategies.

The continuous rise of atmospheric carbon dioxide (CO₂) emissions highlights the urgent need for sustainable air purification technologies. Current Direct Air Capture (DAC) filters often rely on toxic amines, which limit long-term stability and safe application. Here, we report a non-toxic PAN-based nanofiber air filter fabricated by electrospinning and urea-assisted carbonization. Structural analyses confirmed the introduction of nitrogen functionalities that enhanced CO₂ affinity, while SEM and FT-IR revealed graphitic carbon formation. In air-chamber tests, the optimized carbonized nanofiber reduced CO₂ concentration from 25,000 ppm to 2,000 ppm, a level generally regarded as acceptable for indoor environments, while simultaneously removing over 95% of PM₁₀, PM_2.5, and PM_0.1 particulates. This dual functionality, combined with facile fabrication and material safety, demonstrates strong potential for PAN-derived carbon nanofiber membranes in DAC systems and eco-friendly air purification devices. These findings suggest a viable pathway toward scalable, sustainable air-filter technologies for carbon-neutral applications.

(La_1-xBi_xSr_0.3)FeO₃ ceramics exhibiting excellent magnetoresistance were synthesized via the conventional solid-state reaction method. The structural and electrical properties were investigated as a function of Bi³⁺ content to evaluate their potential application as temperature sensors. And the sintering temperature and time were 1,200℃ and 4 h, respectively. The structural and electrical properties were investigated as a function of Bi content. With increasing Bi substitution, a slight enhancement in both average grain size and relative sintered density was observed. In particular, the specimen with x = 0.3 exhibited an average grain size of approximately 0.82 μm. All samples demonstrated negative temperature coefficient of resistance (NTCR) behavior, and the electrical resistivity decreased with increasing Bi content. The resistivity of the (La_0.4Bi_0.3Sr_0.3)FeO₃ composition was 4.68 mΩ-cm at 25°C. Additionally, the temperature coefficient of resistance (TCR) and the B_25/75-value, which quantify the sensitivity of resistivity to temperature variations, were found to increase with Bi content. (La_0.4Bi_0.3Sr_0.3)FeO₃ sample exhibited a TCR of 0.43%/°C and a B_25/75-value of 1,096 K at room temperature. The electrical conduction mechanism of the (La_1-xBi_xSr_0.3)FeO₃ system was well described by the small polaron hopping model, wherein thermally activated charge carriers hop between localized Fe-O-Fe sites via electron-phonon interactions.

The composite specimens of (1-x)(La_0.7Sr_0.3)MnO₃-xBaTiO₃ (x = 0.05 ~ 0.3) were synthesized using the conventional solid-state reaction method, and the sintering temperature and time were 1,300℃ and 3 hours, respectively. As a result of observing the structural characteristics, the crystal structure of LSMO-BT solid solution was shown in which the rhombohedral LSMO phase and the tetragonal BT phase were separated and distributed, respectively. And fine grains having relatively small and uniformly distributed grains with sizes ranging from approximately 0.4 to 0.5 μm and pores within the specimens were observed. Notably, variations in the BT content did not significantly affect the grain size or porosity distribution, and a relative density of about 90% or more was shown. The resistivity, temperature coefficient of resistance (TCR), and B_25/65-value of the 0.7LSMO-0.3BT specimen at room temperature showed the highest values of 1.94 Ω-cm, 0.292 %/℃, and 464 K, respectively. The resistivity behavior of the LSMO-BT composites matched well with the small polaron hopping conduction model.

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.

In this study, we proposed β-Ga₂O₃ JFET using nitrogen doping and analyzed the electrical characteristics. In β-Ga₂O₃, nitrogen ions act as a deep acceptor and are used to implement the current blocking layer. By using this characteristic of the nitrogen ion, in the proposed JFET, nitrogen ions are used to obtain gate control and pinch off the channel of the JFET. The numerical TCAD simulation was performed to design and analyze the proposed JFET. The simulated forward and reverse characteristics of the proposed JFET were obtained as a function of JFET width and nitrogen doping concentration. The maximum breakdown voltage of 1.7 kV was obtained with the on-resistance of 16.7 mΩ·cm² when the channel width was 1.5 μm and nitrogen doping concentration is 1×1018/cm³, respectively.

We investigated the potential of IO:H thin films and hydrogen doping to improve current density and fill factor for enhancing the performance of silicon heterojunction solar cells. We revealed that a transmittance of 86.7% and work function of 5.4 eV could be achieved by injecting 3 sccm of hydrogen gas. The lattice constant of 1.037 nm at the AB site indicates an anion antibonding tendency, and the work function increases as the Fermi level shifts to the valence band. Based on these findings, we fabricated a silicon heterojunction solar cell and achieved an efficiency of 18.53%, while computer simulation confirmed a conversion efficiency of 24.65%, an open-circuit voltage of 724 mV, and a fill factor of 82.72% at a current density of 41.15 mA/㎠.

Department of Electric Materials Engineering, Kwangwoon University, Seoul 01897, Korea (Received June 13, 2024; Revised July 8, 2024; Accepted July 10, 2024) Abstract: Wide bandgap (WBG) devices, especially SiC, are gaining traction as materials for high-power EV conversion devices due to their superior efficiency and switching capabilities compared to Si-based power devices. SiC allows for high power, high temperature, and high frequency applications because of its outstanding thermal conductivity, saturation velocity, and dielectric breakdown field. SiC-based MPS diodes combine the advantages of SiC-based SBDs and PiN diodes, allowing high-frequency switching operation with low leakage currents under high voltage conditions. However, MPS diodes exhibit snapback phenomena influenced by the P⁺ region’s size, necessitating optimization. A TCAD simulation studied the impact of the P+ region’s depth and width on MPS diode performance. Increasing the P⁺ width raised the On-specific resistance (R_on,sp) and lowered the maximum voltage during snapback (V_snap). Increasing the depth decreased both Breakdown voltage (BV) and V_snap. A trade-off between the semiconductor performance index BFOM and V_snap was identified, leading to optimized dimensions. The optimized MPS diode shows a low V_snap of about 3.89 V and a high BFOM of 1.72 GW·㎠, highlighting its potential as a next-generation high-performance power conversion device.

In line with the development of electronic devices and technologies, the demand for improving ferroelectric materials’ performance is increasing. Since K_0.5Na_0.5NbO₃ (KNN), an eco-friendly ferroelectric material that does not use lead and has a high Curie temperature, it is attracting attention to its usability as a high-temperature dielectric, and various studies are being conducted to increase performance. In a KNN having a perovskite structure, there was a simulation result that the KNN has higher spontaneous polarization when the A-site in which sodium ions exist is replaced with lithium ions. If the simulation results can be proven experimentally, the application range of KNN-based ferroelectric materials will increase. To this end, we tried to manufacture a K_1-xLi_xNbO₃ (KLN) with high electrical characteristics by fabricating niobium-deficient and potassium-excessive compositions, which attempt was made to solve the stoichiometry problem by volatilization and suppress secondary phases. If KLN’s secondary phase suppression and relative permittivity improvement are successful, it will contribute to meeting the demand for developing electronic devices.

Mn-doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_2/3Nb_1/3)O₃-PbTiO₃ (Mn:PIN-PMN-PT) single crystals, which exhibit improved phase transition temperatures and coercive field properties compared to Pb(In_1/2 Nb_1/2)O₃-Pb(Mg_2/3Nb_1/3)O₃-PbTiO₃ (PIN-PMNPT) single crystals, are expected to be utilized in high-power acoustic transducers. Bridgeman method, growing single crystals along the axial direction from melt, is most widely used method for single crystal growth with large size and high quality. However, single crystal boules grown by the Bridgeman method demonstrate a PT compositional variation, giving rise a distribution of crystal structure and material properties along the growing axis. To employ piezoelectric single crystals grown by the Bridgeman method for acoustic transducers, it is essential to investigate their overall property distribution. In this study, the compositional distribution and property variation of Mn:PIN-PMN-PT single crystals grown by the Bridgeman method was investigated. Measured compositional distribution of PT was from 29% to 32.5% in the Rhombohedral crystal region of the boule. Two types of specimen, [011]-poled Mn:PIN-PMN-29PT and Mn:PIN-PMN-32PT single crystals, were fabricated and tested to obtain full property variation at both ends of the Rhombohedral crystal region. The properties related to the 32 directional vibration mode and the properties related to high-power driving were measured to confirm the overall distribution of properties by composition.

This work focuses on improving the light-harvesting efficiency of thin-film silicon solar cells through innovative multi-architecture surface modifications. To create a regular optical structure, a lithographic process was performed to form it on a glass substrate through various etching processes, from Etch-1 to Etch-3. AZO was deposited on top of the structures and re-etched to create a multi-architectural surface. These surface-modified structures improved the light absorption and overall performance of the solar cell through changes in optical and physical properties, which we will analyze. In addition, we investigated the effect of post-cleaning on the etched glass structures through EDX analysis to understand the mechanism of the etching action. The results of this study are expected to provide important guidelines for the design and fabrication of solar cells and other photovoltaic devices.

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.

The low-temperature deposition of BaNi_(2-x)Co_xFe₁₆O₂₇ thin films with a Ba hexaferrite structure for electromagnetic shielding was studied. The BaNi_(2-x)Co_xFe₁₆O₂₇ thin films produced through the spin spray process were suitable for thin film deposition on a flexible substrate because it crystallized well at low temperature below 90℃. The change in shielding characteristics depending on the Co content of the BaNi_(2-x)Co_xFe₁₆O₂₇ thin film was investigated, and excellent shielding characteristics with S21 of -1 dB were obtained in a wide frequency range of 26~40 GHz when the Co content was 0.4 or more. The purpose of this study is to analyze changes in shielding properties caused by change in Co content in relation to phase changes in BaNi_(2-x)Co_xFe₁₆O₂₇ and obtain basic data for developing excellent flexible electromagnetic wave shielding materials.

Nitrogen-doped graphene was synthesized by a hydrothermal method using graphene oxide (GO) as the raw material, urea as the reducing agent and nitrogen as the dopant. The morphology, structure, composition and electrochemical properties of the samples are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorptiondesorption analysis, electrical conductivity and electrochemical tests. The results show that urea can effectively reduce GO and achieve nitrogen doping under the hydrothermal conditions. By adjusting the mass ratio of raw materials to dopants, the graphene with different nitrogen doping contents can be obtained; the nitrogen content range is from 5.28~6.08% (atomic fraction percentage).When the ratio of dopant to urea is 1:30, the nitrogen doping content reaches a maximum of 6.08%.The supercapacitor performance test shows that the nitrogen content prepared by the ratio of 6.08% is the best at 0.1 A·g^-1. The specific capacitance is 95.2 F·g^-1.

Multilayered actuators using Pb(Mg_1/3Nb_2/3)O₃-Pb(In_1/2Nb_1/2)O₃-PbTiO₃ (PMN-PIN-PT) crystals have demonstrated excellent properties, but are costly and lack mechanical strength. Textured PMN-PIN-PT ceramics exhibit robust mechanical strength and comparable properties to their single crystals form. However, the development of multilayered actuators using textured PMN-PIN-PT ceramics has not been achieved until now. This study presents the development of a multilayered actuator using textured 0.37PMN-0.29PIN-0.34PT ceramics with an Ag0.9/Pd0.1 inner electrode, co-fired at 950℃. A random 0.37PMN- 0.29PIN-0.34PT ceramics multilayered actuator was also developed for comparison. The multilayered actuator consisted of 9 ceramic layers (36 μm thickness) with an overall actuator thickness of 0.401 mm. The textured and random 0.37PMN-0.29PIN- 0.34PT ceramics-based multilayered actuators achieved displacements of 0.61 μm (0.15% strain) and 0.23 μm (0.057% strain) at a low applied peak voltage of 100 V. These results suggest that the developed multilayered actuator using high-performance textured 0.37PMN-0.29PIN-0.34PT ceramics has the potential to replace expensive single crystal-based actuators costeffectively.

As a potential alternative to flash memory, HfO₂/Al₂O₃ stacks appear to be a viable option as charge capture layers in charge trapping memories. The paper undertakes a review of HfO₂/Al₂O₃ stacks as charge trapping layers, with a focus on comparing the number, thickness, and post-deposition heat treatment and γ-ray and white x-ray treatment of such stacks. Compared to a single HfO₂ layer, the memory window of the 5-layered stack increased by 152.4% after O₂ annealing at ±12 V. The memory window enlarged with the increase in number of layers in the stack and the increase in the Al/Hf content in the stack. Furthermore, our comparison of the treatment of HfO₂/Al₂O₃ stacks with varying annealing temperatures revealed that an increased annealing temperature resulted in a wider storage window. The samples treated with O₂ and subjected to various γ radiation intensities displayed superior resistance. and the memory window increased to 12.6 V at ±16 V for 100 kGy radiation intensity compared to the untreated samples. It has also been established that increasing doses of white x-rays induced a greater number of deep defects. The optimization of stacking layers along with post-deposition treatment condition can play significant role in extending the memory window.

Owing to carbon materials’ diverse functionalization and versatility, the design and synthesis of carbon-based three-dimensional porous structures have become important foundational research topics across various fields. Among the various methods for producing porous carbon structures, laser-induced graphene (LIG) has garnered attention because of its large surface area, controllable structure, excellent electrical conductivity, scalability, and eco-friendly synthesis process. In addition, recent research results have reported more novel functionalities by advancing further from the unique characteristics of LIG through functionalization or compounding of LIG, making it an attractive material for various applications in electronic devices, sensing, catalysis, and energy storage. This review aims to update the research trends in LIG and its functionalization, providing insights to inspire more interesting studies on functional LIG to expand its potential applications ultimately. Starting with the synthesis method and material characteristics of LIG, we introduce the functionalization of LIG, which is classified into surface modification, heteroatom doping, and hybridization based on the interaction mechanism. Finally, we summarize and discuss the prospects of LIG and its functionalization.

Numerical simulation is a good way to predict the conversion efficiency of solar cells without a direct experimentation and to achieve low cost and high efficiency through optimizing each step of solar cell fabrication. TOPCon industrial solar cells fabricated with n-type silicon wafers on a larger area have achieved a higher efficiency than p-type TOPCon solar cells. Electrical and optical losses of the front surface are the main factors limiting the efficiency of the solar cell. In this work, an optimization of boron-doped emitter surface and front electrodes through numerical simulation using “Griddler” is reported. Through the analysis of the results of simulation, it was confirmed that the emitter sheet resistance of 150 Ω/sq along the front electrodes having a finger width of 20 μm, and the number of finger lines ~130 for silicon wafer of M6 size is an optimized technology for the front emitter surface of the n-type TOPCon solar cells that can be developed.

La_0.7Sr_0.3MnO₃ precursor solution were prepared by a sol-gel method. La_0.7Sr_0.3MnO₃ thin films were fabricated by a spin-coating method on a Pt/Ti/SiO₂/Si substrate. Structural and electrical properties with the variation of sintering temperature were measured. All specimens exhibited a polycrystalline orthorhombic crystal structure, and the average thickness of the specimens coated 6 times decreased from about 427 nm to 383 nm as the sintering temperature increased from 740℃ to 830℃. Electrical resistance decreased as the sintering temperature increased. In the La_0.7Sr_0.3MnO₃ thin films sintered at 830℃, electrical resistivity, TCR, B-value, and activation energy were 0.0374 mΩㆍcm, 0.316%/℃, 296 K and 0.023 eV, respectively.

(La_0.5Nd_0.2Sr_0.3)MnO₃ specimens were prepared by a solid-state reaction. In all specimens, X-ray diffraction patterns of an orthorhombic structure were shown. The fracture surfaces of (La_0.5Nd_0.2Sr_0.3)MnO₃ specimens showed a transgranular fracture pattern be possibly due to La ions (0.122 nm) as a perovskite A-site dopant substituting for Nd ions (0.115 nm) having a small ionic radius. The full-width at half maximum (FWHM) of the Mn 2p XPS spectra showed a value greater than that [8] of the single valence state, which is believed to be due to the overlapping of Mn²⁺, Mn³⁺, and Mn⁴⁺ ions. The dependence of Mn 2p spectra on the Mn³⁺/Mn⁴⁺ ratio according to sintering time was not observed. Electrical resistivity resulted in the minimum value of 100.7 Ω-cm for the specimen sintered for 9 hours. All specimens show a typical negative temperature coefficient of resistance (NTCR) characteristics. In the 9-hour sintered specimen, TCR, activation energy, and B25/65-value were -1.24%/℃, 0.19 eV, and 2,445 K, respectively.

The field of liquid crystal display (LCD) is constantly in the spotlight and the process of depositing an alignment layer in the LCD manufacturing process is very important to obtain excellent performance such as low-power driving and high-speed response to improve LCD performance. Therefore, research on liquid crystal (LC) alignment is being actively conducted. When manufacturing LCD, it is necessary to consider the effect of the alignment layer thickness as one of the factors affecting various LCD performances. In addition, previous studies confirmed the LC alignment characteristics correlate with the rotation speed in the spin coating process. Therefore, the electro-optical properties of the LCD were investigated by manufacturing a polyimide alignment layer by varying the rotation speed in the spin coating process in this study. It was confirmed that the thickness of the polyimide alignment layer was controlled according to the spin coating conditions. The average transmittances of anti-parallel LC cells at the spin coating speed of 2,500 rpm and 3,000 rpm are about 60%, which indicates that the LC cell has relatively higher performance. At the spin coating speed of 3,000 rpm, the voltage-transmittance curve of twisted nematic (TN) LC cell was below 1.5 V, which means that the TN LC cell operated at a low power. In addition, high-speed operating characteristics were confirmed with a response time of less than 30 ms. From these derived data, we confirmed that the ideal spin coating speed is 3,000 rpm. And these results provide an optimized polyimide alignment layer process when considering enhanced future LCD manufacturing.

[011] poled ternary Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) single crystals have been investigated for active materials for acoustic transducers because of their high piezoelectric properties in both shear and transverse modes. In order to use [011] poled PIN-PMN-PT single crystals for acoustic transducers, the characterization of full-matrix material properties is required. In this study, full sets of compliance, dielectric, and piezoelectric constants of [011] poled rhombohedral PIN-PMN-PT were measured by a resonance method. Dimensions and geometries of 12 samples were proposed for measuring 17 independent material constants of [011] poled rhombohedral PIN-PMN-PT single crystals. Two sets of samples with different PT concentrations, 0.24PIN-0.49PMN-0.27PT and 0.24PIN-0.46PMN-0.30PT, were fabricated and their material properties were measured. Measured impedance spectra and simulated impedance spectra of the samples were compared to check the accuracy of the measurements.

A diffusion heat treatment process for YBa₂Cu₃O_7-y bulk superconductor in a Gd₂O₃ powder was attempted. As a result of measuring the critical temperature of the superconducting bulk, there was no change in the superconducting transition temperature as the Gd particles diffused into the YBa₂Cu₃O_7-y lattice, resulting in dense microstructure. As a result of measuring the critical current, the critical current density (Jc) of the superconducting bulk having treated by the Gd thermal diffusion treatment at 0 T increased to 3×10⁴ A/㎠ at 0 T, which was higher than that of the superconducting bulk without thermal diffusion treatment. The surface magnetic force of the superconducting bulk with Gd thermal diffusion treatment was observed at the center of the superconducting bulk with the maximum trapped magnetic force (Hmax) of 1.51 kG. This result means that the Gd thermal diffusion treatment contributes to improving the critical current density Jc of YBa₂Cu₃O_7-y, and it is believed that Gd particles migrating into the superconducting bulk through thermal diffusion either fill the surface pores of YBa₂Cu₃O_7-y superconductors or act as a flux pinning center.

Indium-doped Mg_0.05Zn_0.95O thin films were deposited on glass substrates by a sol-gel method. Three types of indium precursors such as indium chloride, indium acetate, and indium nitrate were used as doping sources. Physical properties of fabricated thin films were analyzed through XRD (x-ray diffraction), UV-vis spectrophotometer, Hall effect measurement, and EDS (energy dispersive x-ray spectroscopy). All In-doped thin films grown in this study exhibited a preferred orientation of (002) with over 80% transmittance. The results showed that the Mg_0.05Zn_0.95O thin film from indium chloride as the indium precursor has higher crystallinity and transmittance with lower resistivity when compared with those from other indium precursors.

Non-volatile memory is approaching its fundamental limits with the Si3N4 storage layer, necessitating the use of alternative materials to achieve a higher programming/erasing speed, larger storage window, and better data retention at lower operating voltage. This limitation has restricted the development of the charge-trap memory, but can be addressed by using high-k dielectrics. The paper reviews the doping of nitrogen, titanium, and yttrium on high-k dielectrics as a storage layer by comparing MONOS devices with different storage layers. The results show that nitrogen doping increases the storage window of the Gd₂O₃ storage layer and improves its charge retention. Titanium doping can increase the charge capture rate of HfO₂ storage layer. Yttrium doping increases the storage window of the BaTiO₃ storage layer and improves its fatigue characteristics. Parameters such as the dielectric constant, leakage current, and speed of the memory device can be controlled by maintaining a suitable amount of external impurities in the device.

A series of phosphors, SrWO₄:5 mol% Dy³⁺, SrWO₄:5 mol% Sm³⁺, and SrWO₄:5 mol% Dy³⁺:x Sm³⁺ (x＝1~15 mol%), were prepared using a facile co-precipitation. The crystal structure, morphology, photoluminescence properties, and application in anti-counterfeiting fields were investigated. The crystalline structures of the prepared phosphors were found to be tetragonal systems with the dominant peak occurring at the (112) plane. The excitation spectra of the Dy³⁺ singly-doped SrWO₄ phosphors were composed of an intense charge-transfer band centered at 246 nm in the range of 210~270 nm and two weak peaks at 351 nm and 387 nm due to the ⁶H_15/2→⁶P_7/2 and ⁶H_15/2→⁴I_13/2 transitions of Dy³⁺ ions, respectively. The wavelength of 246 nm was optimum for exciting the luminescence of Dy³⁺ and Sm³⁺ co-doped SrWO₄ phosphors. The emission spectra consisted of two intense blue and yellow emission bands at 480 nm and 573 nm corresponding to the ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions of Dy³⁺, and two strong emission peaks at 599 nm and 643 nm originating from the ⁴G_5/2→⁶H_7/2 and ⁴G_5/2→⁶H_9/2 transitions of Sm³⁺, respectively. As the concentration of Sm³⁺ ions increased, the emission intensities of Dy³⁺ rapidly decreased, while the emission intensities of Sm³⁺ gradually increased. These results suggest that the color of the emission light can be tuned from yellow to white by changing the concentration of Sm³⁺ ions at a fixed 5 mol% Dy³⁺. Furthermore, the fluorescent security inks were synthesized for use in anti-counterfeiting applications.

In this study, Mg_xZn_1-xO thin films, which can be applied not only to active layers of light-emitting devices (LEDs), such as UV-LEDs, but also to solar cells, high mobility field-effect transistors, and power semiconductor devices, are fabricated using the sol-gel method. ZnO and Mg_0.3Zn_0.7O solution synthesized by the sol-gel method and the thin film were grown by spin coating on a Si (100) substrate and sapphire substrate. The solutions are synthesized by dissolving precursor materials in 2-methoxyethanol (2-ME) solvent, and then monoethanolamine (MEA) was added to the mixed solution as a sol stabilizer. Zinc acetate dihydrate is used as a ZnO precursor, while Mg nitrate hexahydrate and Mg acetate tetrahydrate are used as an MgO precursor. Then, the optical and structural characteristics of the fabricated thin films are compared. The molar concentration of the Zn precursor in the solvent is fixed at 0.3 M, and the amount of the Mg precursor is 30% of Mg²⁺/Zn²⁺. The optical characteristics are measured using an UV-vis spectrophotometer, and the transmittance of each wavelength is measured. Structural characteristics are measured using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Composition analyses are performed using energy dispersive X-ray spectroscopy (EDS). The Mg_0.3Zn_0.7O thin film was well formed at the ratio of the Mg precursor added regardless of the type of Mg precursor, and the c-axis of the thin film was decreased, while the band gap was increased to 3.56 eV.

Relatively pure YBCO was first synthesized by heating a mixture of metal carbonates at temperatures between 1,000 and 1,300 K, resulting in the reaction: 4BaCO₃＋Y₂(CO₃)₃＋6CuCO₃＋(1/2_-x)O₂ → 2YBa₂Cu₃O_7-x＋1/3CO₂. Modern syntheses of YBCO use the corresponding oxides and nitrates. The superconducting properties of YBa₂Cu₃O_7-x are sensitive to the value of x, i.e., its oxygen content. Only those materials with 0≤x≤0.65 are superconducting below Tc, and when x ~ 0.07, the material superconducts at the highest temperature, i.e., 95 K, or in the highest magnetic fields, i.e., 120 T and 250 T when B is perpendicular and parallel to the CuO₂ planes, respectively. In addition to being sensitive to the stoichiometry of oxygen, the properties of YBCO are influenced by the crystallization methods applied. YBCO is a crystalline material, and the best superconductive properties are obtained when crystal grain boundaries are aligned by careful control of annealing and quenching temperature rates. However, these alternative methods still require careful sintering to produce a quality product. New possibilities have arisen since the discovery of trifluoroacetic acid, a source of fluorine that prevents the formation of undesired barium carbonate (BaCO₃). This route lowers the temperature necessary to obtain the correct phase at around 700℃. This, together with the lack of dependence on vacuum, makes this method a very promising way to achieve a scalable YBCO bulk.

Boron nitride (BN) nanofibers were fabricated using BN nanoparticles (70 nm) by electrospinning. Morphologies such as the diameter and density of the BN nanofibers are strongly influenced by the viscosity and dispersion state of the precursor solution. In this study, the precursor solution was prepared by ball milling BN nanoparticles and polyvinylpyrrolidone (PVP, Mw~1,300,000) in ethanol, which was electrospun and then calcined to produce BN fibers. High-quality BN nanofibers were well fabricated at a BN concentration of 15 wt% with their diameters in the range of 500 nm to 800 nm; the viscosity of the precursor solution was 400 mPa·S. The calcination of the as-electrospun BN fibers seemed to be completed by holding them at 350℃ for 2 h considering the TGA data. The morphologies and phases of the BN fibers were investigated by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively; Fourier transform infrared (FT-IR) was also used for structure analysis.

Silicon carbide is widely used in power semiconductor devices owing to its high energy gap. In particular, Schottky barrier diode (SBD) and PiN diodes fabricated on 4H-SiC wafers are being applied to various fields such as power devices. The characteristics of SBD and PiN diodes can be extracted from C-V and I-V characteristics. The measured Schottky barrier height (SBH) was 1.23 eV in the temperature range of 298~473 K, and the average ideal factor is 1.17. The results show that the device with the Schottky contact is characterized by the theory of thermal emission. As the temperature increases, the parameters are changed and the Vth is shifted to lower voltages.