To ensure high-voltage stability and thermal resistance of insulation paper used in transformers, this study evaluated the structural and electrical properties of four types of insulation paper samples fabricated using unbleached kraft pulp (UKP). The samples were prepared under controlled conditions with different freeness levels (300-700 ml). Tensile strength, dielectric constant, breakdown strength (dry and oil), volume resistivity, water absorption, and oil absorption were quantitatively measured. The sample with a beating degree of 300 exhibited the highest breakdown strength (53.85 kV/mm) and volume resistivity (1.49×10¹⁶ Ω·cm), whereas the samples with higher beating intensity showed improved fiber bonding and densification. These findings demonstrate the practical applicability of UKP-based insulation paper as a high-performance, eco-friendly insulating material for transformer systems, providing a scientific foundation for process optimization in insulation paper design.

Piezoelectric materials, which convert mechanical energy into electrical signals, are widely used in various industrial applications such as sensors, actuators, and energy harvesting devices. This study aims to enhance the performance of Pb(Mg_1/3Nb_2/3)O₃-Pb(Al_1/2Nb_1/2)O₃-Pb(Zr_0.52Ti_0.48)O₃ (PMN-PAN-PZT) piezoelectric ceramics by investigating the effects of varying PAN and PMN content and adding Nb₂O₅ on their piezoelectric properties. The results show that with 2 mol% of PMN and PAN, the morphotropic phase boundary (MPB) region exhibits the highest piezoelectric properties. Additionally, excess Nb₂O₅ positively influenced the piezoelectric properties, maximizing electro-mechanical coupling factor (k_p=63%, d₃₃=440 pC/N). These findings contribute to developing next-generation high-performance piezoelectric materials, with potential for improved efficiency and performance in various industries.

In this study, KTN heterolayer thin films were fabricated by alternately stacking films of K(Ta_0.70Nb_0.30)O₃ and K(Ta_0.55Nb_0.45)O₃ synthesized using the sol-gel method. The sintering temperature and time were 750℃ and 1 hour, respectively. All specimens exhibited a polycrystalline pseudo-cubic crystal structure, with a lattice constant of approximately 0.398 nm. The average grain size was around 130~150 nm, indicating relatively uniform sizes regardless of the number of coatings. The average thickness of a single-coated film was approximately 70 nm. The phase transition temperature of the KTN heterolayer films was found to be approximately 8~12℃. Moreover, the 6-coated KTN heterolayer film displayed an excellent dielectric constant of about 11,000. As the number of coatings increased, and consequently the film thickness, the remanent polarization increased, while the coercive field decreased. The 6-coated KTN heterolayer film exhibited a remanent polarization and coercive field of 11.4 μC/cm² and 69.3 kV/cm at room temperature, respectively. ΔT showed the highest value at a temperature slightly above the Curie temperature, and for the 6-coated KTN heterolayer film, the ΔT and ΔT/ΔE were approximately 1.93 K and 0.128×10^-6 K·m/V around 40℃, respectively.

The advantage of OTFT technology is that large-area circuits can be manufactured on flexible substrates using a lowcost solution process such as inkjet printing. Compared to silicon-based inorganic semiconductor processes, the process temperature is lower and the process time is shorter, so it can be widely applied to fields that do not require high electron mobility. Materials that have utility as electrode materials include carbon that can be solution-processed, transparent carbon thin films, and metallic nanoparticles, etc. are being studied. Recently, a technology has been developed to facilitate charge injection by coating the surface of the Al electrode with solution-processable titanium oxide (TiOx), which can greatly improve the performance of OTFT. In order to commercialize OTFT technology, an appropriate method is to use a complementary circuit with excellent reliability and stability. For this, insulators and channel semiconductors using organic materials must have stability in the air. In this study, carbon-doped Mo (MoC) thin films were fabricated with different graphite target power densities via unbalanced magnetron sputtering (UBM). The influence of graphite target power density on the structural, surface area, physical, and electrical properties of MoC films was investigated. MoC thin films deposited by the unbalanced magnetron sputtering method exhibited a smooth and uniform surface. However, as the graphite target power density increased, the rms surface roughness of the MoC film increased, and the hardness and elastic modulus of the MoC thin film increased. Additionally, as the graphite target power density increased, the resistivity value of the MoC film increased. In the performance of an organic thin film transistor using a MoC gate electrode, the carrier mobility, threshold voltage, and drain current on/off ratio (I_on/I_off) showed 0.15 cm²/V·s, -5.6 V, and 7.5×10⁴, respectively.

In this paper, for the application of ultrasonic cleaners for cleaning dentures and transparent braces, Pb(Mn_1/3Nb_2/3)O₃-Pb(Ni_1/3 Nb_2/3)O₃-Pb(Zr,Ti)O₃ [PMN-PNN-PZT] system ceramics were manufactured and their dielectric and piezoelectric properties were investigated. Overall the best properties suitable for the device applications such as ultrasonic cleaner were obtained from the ceramics sintered at 920℃: bulk density of 7.8 g/㎤, the dielectric constant (ε_r) of 1,689, piezoelectric charge constant (d₃₃) of 433 pC/N, planar electromechanical coupling factor (k_p) of 0.64, mechanical quality factor (Qm) of 835, S₁₁^E of 13.37 (10^-12 N/㎡), and Curie temperature of 315℃ By using the physical properties of this composition, the ultrasonic cleaner was designed and simulated using the commercial ATILA software. For the three-layered ceramics with the dimension of 25 mm × 25 mm × 2.5mm, an excellent displacement of 8.998 ×10^-3 m) and the sound pressure of 147.68 dB were recorded.

In this work, the (K_1-xAg_x)(Ta_0.8Nb_0.2)O₃ (x=0.1-0.4) ceramics were fabricated using mixed-oxide method, and their structural and electrical properties were measured. All specimens represented a pseudo cubic structure with the lattice constant of 0.3989 nm. When 0.4 mol of Ag was added, second phases induced from metallic Ag and K₂(Ta,Nb)₆O₁₆ phase were observed. Dielectric constant and dielectric loss of K(Ta_0.8Nb_0.2)O₃ specimen doped with 0.3 mol of Ag were 2,737 and 0.446, respectively. The curie temperature was about -5℃, which does not change with Ag addition. The remanent polarization began to decrease sharply around 12~15℃, and the temperature at which the remanent polarization began to decrease as the applied voltage increased shifted to the high temperature side. The electrocaloric effect (ΔT) and electrocaloric efficiency (ΔT/ΔE) of the (K_0.7Ag_0.3)(Ta_0.8Nb_0.2)O₃ ceramics were 0.01024℃ and 0.01825 KmV^-1, respectively.

Developing a thin-film transistor with characteristics such as a large area, high mobility, and high reliability are key elements required for the next generation on displays. In this paper, we have investigated the research trends related to improving the reliability of oxide-semiconductor-based thin-film transistors, which are the primary focus of study in the field of optical displays. It has been reported that thermal treatment in a high-pressure oxygen atmosphere reduces the threshold voltage shift from -7.1 V to -1.9 V under NBIS. Additionally, a device with a SiO₂/Si₃N₄ dual-structure has a lower threshold voltage (-0.82 V) under NBIS than a single-gate-insulator-based device (-11.6 V). The dual channel structure with different oxygen partial pressures was also confirmed to have a stable threshold voltage under NBIS. These can be considered for further study to improve the NBIS problem.

Raman spectra of a-C:H thin films deposited with an unbalanced magnetron sputtering system showed that the G peak shifted to a higher wavenumber as the target power density increased and ID/IG ratio increased from 0.902 to 1.012. Moreover, the transmittance of a-C:H films fabricated at 60 nm tended to decrease with increasing target power density; at 550 nm in the visible light region, the transmittance decreased from 69% to 58%. The rms surface roughness values of the a-C:H thin films decreased with increasing target power density, and varied from 1.11 nm to 0.71 nm. In order to achieve efficient light trapping, the light scattering at the rough interface must be enhanced. Consequently, the surface roughness of the thin film will decrease with the target power density. Further, the refractive index and reflectivity of the a-C:H thin films increased with increasing target power density; however, the Brewster angle decreased with the target power density. Hence, dye-sensitized solar cells using an a-C:H antireflective coating increased the CE, VOC, and JSC by approximately 8.6%, 5.5%, and 4.5%, respectively.

TiN thin films were fabricated using an unbalanced magnetron sputtering (UBMS) system, and their structure and surface characteristics as well as their optical and tribological properties were evaluated. The hardness, elastic modulus, adhesive force, surface roughness, and transmittance of the Ti thin films fabricated using the UBMS system were 11.5 GPa, 103 GPa, 27.5 N, 2.45 nm and 20%, respectively. The TiN films prepared with various proportions of nitrogen as the reaction gas exhibited maximum values for the hardness, elastic modulus, critical load, RMS roughness and transmittance of approximately 19.2 GPa, 182 GPa, 27.3 N, 0.98 nm, and 85%, respectively. Moreover, the TiN thin film fabricated under the condition of 30 sccm nitrogen gas showed the optimal physical properties. In summary, the TiN thin films fabricated using the UBMS system exhibited excellent hardness, elastic modulus, adhesion, and smooth surface in addition to good hydrophilic properties.

We investigated the tribological properties of amorphous carbon (a-C) films deposited with CrC interlayers of various thicknesses as the adhesive layer. A-C and CrC thin films were deposited using the unbalanced magnetron (UBM) sputtering method with graphite and chromium as the targets. CrC films as the interlayer were fabricated under a-C films, and various structural, surface, and tribological properties of a-C films deposited with various CrC interlayer thicknesses were investigated. With various CrC interlayer thicknesses under a-C films, the tribological properties of CrC/a-C films were improved; the increased film thickness exhibited a maximum high hardness of over 27.5 GPa, high elastic modulus of over 242 GPa, critical load of 31 N, residual stress of 1.85 GPa, and a smooth surface below 0.09 nm at the condition of 30-nm CrC thickness.

In this study, double layer KTN/STO thin films were fabricated on Pt/Ti/SiO₂/Si substrate, their structural and electrical properties were measured according with the number of STO coatings, and their applicability to microwave materials was investigated. The average grain size was about 80~90 nm, the average thickness of the 6-coated KTN thin film was about 320 nm, and the average thickness of the STO thin film coated once was about 45~50 nm. The dielectric constant decreased with increasing frequency, and as the number of STO coatings increased, the rate of change of the dielectric constant with the applied electric field decreased. The tunability of the KTN thin film showed a maximum value of 19.8% at 3 V. The figure of merit of the KTN/1STO thin film was 9.8 at 3 V.

Various Ni-doped carbon (C：Ni) thin films were fabricated using different Ni target power densities by unbalanced magnetron sputtering (UBM). The effects of target power density on the structural, physical, surface, and electrical properties of C：Ni films were investigated. The UBM C：Ni thin films exhibited uniformly smooth surfaces. The rms surface roughness and friction coefficient values of the C：Ni films decreased with the increase in target power density. The physical properties of the films such as hardness and elastic moduli increased while their electrical properties such as resistivity decreased with the increase in the target power density. These results show that an increase of the power density leads to an increase in the proportion of Ni and nanocrystallization of the amorphous carbon film; this contributes to the changes observed in the physical and electrical characteristics.

Mo doped carbon (C:Mo) thin films were fabricated with various Mo target power densities by unbalanced magnetron sputtering (UBM). The effects of target power density on the surface, structural, and electrical properties of C:Mo films were investigated. UBM sputtered C:Mo thin films exhibited smooth and uniform surfaces. However, the rms surface roughness of C:Mo films were increased with the increase of target power density. Also, the resistivity value of C:Mo film as electrical properties was decreased with the increase of target power density. From the performance of organic thin filml transistor using conductive C:Mo gate electrode, the carrier mobility, threshold voltage, and on/off ratio of drain current (Ion/Ioff) showed 0.16 cm²/V·s, -6.0 V, and 7.7×10⁴, respectively.

Prevailing dissemination of machine tools and cutting technology have caused drastic developments of high speed dry machining with work materials of high hardness, and demands on the high-hardness-materials with high efficiency have become increasingly important in terms of productivity, cost reduction, as well as environment-friendly issue. Addition of Si to TiAlN has been known to form nano-composite coating with higher hardness of over 30 GPa and oxidation temperature over 1,000℃. However, it is not easy to add Si to TiAlN by using conventional PVD technologies. Therefore, Ti-Al-Si-N have been prepared by hybrid process of PVD with multiple target sources or PVD combined with PECVD of Si source gas. In this study, a single composite target of Ti-Al-Si was prepared by powder metallurgy of MA (mechanical alloying) and SPS (spark plasma sintering). Properties of he resulting alloying targets were examined. They revealed a microstructure with micro-sized grain of about 1~5 ㎛, and all the elements were distributed homogeneously in the alloying target. Hardness of the Ti-Al-Si-N target was about 1,127 Hv. Thin films of Ti-Al-Si-N were prepared by unbalanced magnetron sputtering method by using the home-made Ti-Al-Si alloying target. Composition of the resulting thin film of Ti-Al-Si-N was almost the same with that of the target. The thin film of Ti-Al-Si-N showed a hardness of 35 GPa and friction coefficient of 0.66.

Titanium oxide (TiO2) thin films were fabricated by unbalanced magnetron (UBM) sputtering. The fabricated TiO2 films were treated by oxygen plasma under various RF powers. We investigated the characteristics of oxygen plasma treatment on the surface, structural, and physical properties of TiO2 films prepared at various plasma treatment RF powers. UBM sputtered TiO2 films exhibited higher contact angle value, smooth surface, and amorphous structure. However, the rms surface roughness TiO2 films were rough, and the contact angle value was decreased with the increase of the plasma treatment RF power Also, the hardness value of TiO2 film as physical properties was slightly increased with the increase of the plasma treatment RF power. In the results, the performance of TiO2 films for self cleaning critically depended on the with the plasma treatment RF power.

The characterizations of zinc oxide (ZnO) buffer layers grown by unbalanced magnetron (UBM) sputtering under various substrate temperatures for inverted organic solar cells (IOSCs) were investigated. UBM sputter grown ZnO films exhibited higher crystallinity with increasing the substrate temperature, resulting in uniform and large grain size. Also, the electrical properties of ZnO films are improved with increasing substrate temperature. In the results, the performance of IOSCs critically depended on the substrate temperature during the film growth because the crystalllinity of the ZnO film affect the carrier mobility of the ZnO film.

(Na,K)NbO3-based piezoelectric ceramics were synthesized by a solid phase sintering method with various milling solvents. The solvents were varied with acetone, ethanol, and pure water to investigate the effect on the microstructure and electrical properties. NKN ceramics showed the maximum values of the relative density (94%), the mechanical quality factor (Qm: 78) and the electro-mechanical coupling factor (kp: 0.25) at the ethanol solvent. It might mean that a solid phase sintering of the NKN piezoelectrics with a suitable solvent could improve the relative density and the piezoelectric properties.

Channel length dependence of NBTI (negative bias temperature instablilty) and CHC (channel hot carrier) characteristics in PMOSFET is studied. It has been considered that HC lifetime of PMOSFET is larger than NBTI lifetime. However, it is shown that CHC degradation is greater than NBTI degradation for PMOSFET with short channel length. 1/f noise and charge pumping measurement are used for analysis of these degradations.

TiC thin films were deposited on Si wafer by unbalanced magnetron sputtering (UBMS) system with two targets of graphite and titanium. During the TiC sputtering, the RF power was varied from 100 W to 175 W and the physical and electrical properties of TiC films were investigated. The hardness and rms surface roughness of TiC films were improved with increasing RF power and the maximum hardness about 24 GPa and the minimum rms surface roughness about 1.2 nm were obtained. The resistivity of TiC films was decreased with increasing RF power. Consequently, the physical and electrical properties of TiC film wewe improved with increasing RF power.

In this study, lead-free Piezoelectric (Na0.47K0.47Sr0.03Ca0.03)(Nb0.94Ti0.06)O3-0.1 MnO2 ceramics werefabricated using mixed oxide method and the effects of various sintering temperature on the structural andelectrical properties were investigated. For the (Na0.47K0.47Sr0.03Ca0.03)(Nb0.94Ti0.06)O3-0.1 MnO2 (NKN-SCT-MnO2)ceramics sintered at temperatures of 1,025∼1,100℃. The results indicated that all specimens were perovskitesingle phase formation without any second phase. It has been shown that relative density is increased toincreasing sintering temperature. When the sintered temperature at 1,075℃, highest sintered density andmaximum value of 4.45 g/cm3. Average grain size is increased to increasing sintering temperature. Theelectromechanical coupling factor, dielectric constant, dielectric loss, d33 and curie temperature at the sinteringtemperature 1,075℃ of NKN-SCT-MnO2 specimens were 0.22, 511, 0.033, 103 and 380℃, respectively.

In this study, KNbO3-substituted (Li,Na,K)(Nb,Sb,Ta)O3 ceramics were investigated to develop Pb-free composition ceramics for multilayer actuator and energy harvester applications. The X-ray diffraction analysis indicated that all samples were pure perovskite phase and no secondary phase was found. A tetragonality as a function of KNbO3 substitution showed the maximum value at 1.5 mol% KNbO3 and then decreased. The SEM image analysis showed the maximum grain size of 3.14 ㎛ at 1.5mol% KNbO3. In the composition ceramics with 1.5 mol% KNbO3 sintered at 1,100℃, excellent properties of density= 4.75 g/cm3, electromechanical coupling factor (kp)= 0.50 and piezoelectric constant(d33)= 290 pC/N were obtained, respectively, suitable for piezoelectric actuator and energy harvester applications.

Niobium oxide(Nb2O5) films were deposited on p-type Si wafers at room temperature using in-line pulsed-DC magnetron sputtering system with various frequencies. The different duty ratios were obtained by varying the frequency of pulsed DC power from 100 to 300 kHz at the fixed reverse time of 1.5 μs. From the thickness of the sputtered NbOx films, it was possible to obtain much higher deposition rate in case of pulsed-DC sputtering than RF sputtering. However, the similar leakage currents and structural characteristics were obtained from the metal-insulator-semiconductor(MIS) structure fabricated with the NbOx films and the x-ray photoelectron spectroscopy(XPS) results in spite of the different deposition rates. From the experimental results, the NbOx films sputtered by pulsed-DC sputtering are expected to be used in the fabrication process instead of RF sputtering.

In this study, in order to develop excellent lead free piezoelectric ceramics for piezoelectric actuators application, Li0.04(Na0.50K0.50)0.96[(Nb0.86Ta0.10Sb0.04)0.994Co0.015]O3+0.0025SrO + 0.15 wt%K2CO3 + x wt%Nb2O5 (x = 0 - 0.5 wt%) (abbreviated as LNKNTSCS-xN) ceramics were fabricated by a conventional sintering technique. the phase structure, microstructure and electrical properties were investigated with a emphasis on the influence of the Nb2O5 content. High electrical properties of d33= 234 pC/N, kp= 0.392, εr= 1,395, ρ= 4.70 g/cm3 were obtained from the specimen with x= 0.4 wt%, which suggests that the composition ceramics is a promising lead-free piezoelectric material.

Multifunctional structures with two kinds of materials have been intensively investigated in order to improve their electrical characteristic with two functions simultaneously. However, the research regarding of multifunctional ceramic sensor is still in a preliminary stage and how to integrate them with low-cost and high-yield mass production process remains a challenge issue. In this study, we fabricated the multifunctional ceramic sensor composed of temperature and gas sensors. Moreover, we investigated the CO sensing properties of three dimensional nanostuctured Nb2O5 thin film gas sensors fabricated with silica (SiO2) nanosphere (Ø= 750 nm). Compared to plain films, the nanostructured films show enhanced gas sensing of greater sensitivity and a faster response. This result reveals that significantly increased sensitivity is an increase in the effective surface area for the adsorption of gas molecules.

TiO2 (Ti(1-x)Nb(x)O2, x= 0.04~0.06) transparent conducting oxide film was fabricated by RF magnetron sputtering process and their electrical, optical, stability properties were studied. When the Nb 4 at% sputtering target was used with RF power 120 W, pressure 8 mTorr, post-annealing temperature 60 0℃, the resistivity of TNO film was 4×10(-4) Ω-cm. The optical transmittance in the visible wavelength was ca. 86%. TNO films require heat treatment during or after the deposition process. When the film was deposited at room temperature and post-annealed at 600℃, the lowest resistivity was obtained. When the TNO film was exposed to high temperature and humidity, the resistivity of the film was rather decreased. The stability to temperature and humidity implies that the TNO film could be a appropriate candidate for In-free, ZnO-free transparent conducting oxide materials.

In this study, we fabricated an amorphous InGaZnO pseudo-MOS transistor (a-IGZO Ψ -MOSFET) with a stacked Si3N4/SiO2 (NO) gate dielectric and evaluated reliability of the devices with various thicknesses of a SiO2 buffer layer. The roles of a SiO2 buffer layer are improving the interface states and preventing degradation caused by the injection of photo-created holes because of a small valance band offset of amorphous IGZO and Si3N4. Meanwhile, excellent electrical properties were obtained for a device with 10-nm-thick SiO2 buffer layer of a NO stacked dielectric. The threshold voltage shift of a device, however, was drastically increased because of its thin SiO2 buffer layer which highlighted bias and light-induced hole trapping into the Si3N4 layer. As a results, the pseudo-MOS transistor with a 20-nm-thick SiO2 buffer layer exhibited improved electrical characteristics and device reliability; field effective mobility(μFE) of 12.3 cm2/V·s, subthreshold slope (SS) of 148 mV/dec, trap density (Nt) of 4.52× 1011 cm-2, negative bias illumination stress (NBIS) ΔVth of 1.23 V, and negative bias temperature illumination stress (NBTIS) ΔVth of 2.06 V.

Perovskite niobates and tantalates have been placed on a short list of functional materials for future technologies. This article was investigated ferroelectric materials Ag(Ta,Nb)O3 thick film. In this study, we have fabricated the Ag(Ta,Nb)O3 thick film on the Al2O3 substrates by screen printing method. The Ag(Ta,Nb)O3 thick film were fabricated by the mixed oxide method. The sintering temperature and time were 1,150℃, 2 hr. The electrical properties of Ag(Ta,Nb)O3 thick film were investigated at 30∼100℃.

In this study, the effect of Nb2O5 and sintering time on the positive temperature of coefficient of resistivity (PTCR) behavior of lead free Ba0.99(Bi0.5Na0.5)0.01TiO3 (BBNT) ceramics were investigated in order to fabricate a PTC thermistor with high Tc temperature more than 140℃. In particular, BBNT ceramic doped with 0.1mol% Nb2O5 and sintered at 1350℃ for 4 h has significantly increased Curie temperature (Tc) of about 200℃, showed good PTCR behavior of room-temperature resistivity (ρrt) of 40 Ω·㎝, a high ρmax/ρmin ratio of 43.78×103 and a large resistivity temperature factor (α) of 16.1%/℃. With increasing addition of Nb2O5 content, the ρrt decreased to a minimum value of 40 Ω·㎝ at 0.1mol% Nb2O5 and the ρrt increased for x value over 0.1 mol%.

The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of 0.96(K0.5Na0.5)NbO3-0.04SrZrO3+x mol% ZrO2 [KNN-SZ+xZrO2; x= 0～0.10] doped with 0.1 wt% MnO2 by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%H2-97%N2 atmosphere at 1,140℃ exhibit pure perovskite structure irrespective of the content of ZrO2. Meanwhile, the sintering denisty and piezoelectric properties such as Kp, Qm and d33 of KNN-SZ samples as a function of ZrO2 content show the maxima (kp= 28.07%, Qm= 101.34, d33= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+xZrO2 composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.