In the study, the characteristics of the etched Zinc oxide (ZnO) thin films surface, the etch rate of ZnO thin film in Cl2/BCl3/Ar plasma was investigated. The maximum ZnO etch rate of 53 nm/min was obtained for Cl2/BCl3/Ar=3:16:4 sccm gas mixture. According to the x-ray diffraction (XRD) and atomic force microscopy (AFM), the etched ZnO thin film was investigated to the chemical reaction of the ZnO surface in Cl2/BCl3/Ar plasma. The field emission auger electron spectroscopy (FE-AES) analysis showed an elemental analysis from the etched surfaces. According to the etching time, the ZnO thin film of etched was obtained to The AES depth-profile analysis. We used to atomic force microscopy to determine the roughness of the surface. So, the root mean square of ZnO thin film was 17.02 in Cl2/BCl3/Ar plasma. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the plasmas.

The etching characteristics of indium tin oxide (ITO) thin films in an O2/BCl3/Ar plasma were investigated. The etch rate of ITO thin films increased with increasing O2 content from 0 to 2 sccm in BCl3/Ar plasma, whereas that of ITO decreased with increasing O2 content from 2 sccm to 6 sccm in BCl3/Ar plasma. The maximum etch rate of 65.9 nm/m in for the ITO thin films was obtained at 2 sccm O2 addition. The etch conditions were the RF power of 500 W, the bias power of 200 W, the process pressure of 15 mTorr, and the substrate temperature of 40℃. The analysis of x-ray photo electron spectroscopy (XPS) was carried out to investigate the chemical reactions between the surfaces of ITO thin films and etch species.

In this investigation, the effects of N(2)/(Ar+N(2)) gas partial pressure on the structural, electrical, and thermal properties of AlN dielectric layers prepared on aluminum substrates using RF-magnetron sputtering method were analyzed. Among the films, the AlN dielectric film deposited under N(2)/(Ar+N(2)) gas partial pressure of 75% exhibit the highest AlN (002) preferred orientation, which was grain size of about 15.3(2) nm and very dense structure. We suggest the possibilities of it`s application as a dielectric layer for metal PCB because the AlN films prepared at optimized gas partial pressure can improving the insulating property, the thermal conductivity, and thermal diffusivity of the films.

By improving the conducting process of metal source/drain (S/D) in direct contact with the channel, schottky barrier metal-oxide-semiconductor field effect transistors (SB MOSFETs) reveal low extrinsic parasitic resistances, offer easy processing and allow for well-defined device geometries down to the smallest dimensions. In this work, we investigated the arrhenius plots of the SB MOSFETs with different S/D schottky barrier (SB) heights between simulated and experimental current-voltage characteristics. We fabricated SB MOSFETs using difference S/D metals such as Cr (ФCr~4.5 eV) and Ni (ФNi~5.2 eV), respectively. Schottky barrier height (ФB) of the fabricated devices were measured to be 0.25~0.31 eV (Cr-S/D device) and 0.16~0.18 eV (Ni-S/D device), respectively in the temperature range of 300 K and 475 K. The experimental results have been compared with 2-dimensional simulations, which allowed bandgap diagram analysis.

In this work, we investigated the static characteristics of 4H-SiC vertical metal-oxide- semiconductor field effect transistors (VMOSFETs) by adjusting the doping level of n-epilayer and the effect of a current spreading layer (CSL), which was inserted below the p-base region with highly doped n+ state (5 x 1017 cm-3). The structure of SiC VMOSFET was designed by using a 2-dimensional device simulator (ATLAS, Silvaco Inc.). By varying the n-epilayer doping concentration from 1×1016 cm-3 to 1×1017 cm-3, we investigated the static characteristics of SiC VMOSFETs such as blocking voltages and on-resistances. We found that CSL helps distribute the electron flow more uniformly, minimizing current crowding at the top of the drift region and reducing the drift layer resistance. For that reason, silicon carbide VMOSFET structures of highly intensified blocking voltages with good figures of merit can be achieved by adjusting CSL and doping level of n-epilayer.

In this study, piezoelectric and dielectric properties of the (Na0.5K0.5)NbO3-(1-x)(Bi0.5Na0.5)TiO3- xBaTiO3 [NKN-(1-x)BNT-xBT] ceramics were investigated. The lead-free NKN-(1-x)BNT-xBT ceramics were fabricated by a conventional mixed oxide method. The results indicate that the addition of BaTiO3 significantly influences the sintering, microstructure, phase transition and electrical properties of NKN-BNT ceramics. A gradual change in the piezoelectric and dielectric properties was observed with the increase of BT contents. The dielectric constant, piezoelectric constant (d33) and electromechanical coupling factor (kp) increased at the morphotropic phase boundary (MPB). The d33=184 pC/N, kp=0.38, dielectric constant=1455 with dielectric loss value of less than 1% were obtained for the NKN-0.95BNT-0.05BT ceramics sintered at 1150℃ for 2h. These results demonstrate that the NKN-(1-x)BNT-xBT ceramics is an attractive candidate for lead-free piezoelectric materials.

CdSe films were deposited on glass substrates (CdSe/glass) by thermal evaporation. Substrate temperature was lowered by cooling substrate holder with liquid nitrogen. Substrate temperatures were 200℃, 0℃ and -40℃. The crystallographic properties and surface morphologies of the CdSe/glass films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The optical and electrical properties of the films were investigated by dependence of energy gap, photosensitivity and resistivity on the substrate temperature. CdSe/glass showed energy gap of ～1.72 eV regardless of substrate temperature. The resistivity of the films decreased to 0.5 Ωcm by lowering the substrate temperature to -40℃. The CdSe/glass films prepared at 0℃ showed the highest photosensitivity among the films in this study.

Recently the solution-based thin film technology has often been treated in the field of device fabrication owing to easy process and convenience for the development of various semiconductor devices and sensors. We deposited on glass substrate single-walled carbon nanotubes (SWNTs)/silane hybrid thin films by multiple spray-coating which is one of solution-based processes, and examined their electrical response for humidity. Generally silane binders which are often mixed in carbon nanotube (CNT) solution to adhere CNTs to substrate well form easily each own functionalized group on the surface of CNTs after they are hardened by way of the hydrolysis reaction. In this work, we investigated how silane binders (TEOS (tetraethoxy silane), MTMS (methyltrimethoxysilane) and VTMS (vinyltrimethoxysilane)) in CNT thin films make effect to their electrical response on humidity. As the result, we found that the resistance in the samples using TEOS was changed dramatically while it was almost invariant in the samples using MTMS and VTMS for increasing humidity.

The yttrium-barium-copper-oxide (YBCO) coated conductor, which supplement the fault of the existing superconducting current-limit materials YBCO thin film, bismuth-strontium-calcium-copper-oxide(BSCCO) wire and bulk, has been improved its mechanical weakness and has high index; hence, after quench YBCO coated conductor could limit the fault current effectively because of fast resistance occurrence speed. Furthermore, it has wide applicable area as an current limit material because it shows different resistance occurrence tendency by the thickness and kind of stabilization material sputtered on the superconducting layer. Therefore, many researchers are carrying out the study of application of YBCO coated conductor to superconducting fault current limiter (SFCL) for making high quality current limit element, based on resistance type. On the other hand, the study for other type except resistance type has been rarely conducted for the application of YBCO coated conductor to SFCL as an current limit element. Consequently, in this study, YBCO coated conductor with different stabilization layer Cu and Stainless steel, is applied to SFCL using iron core and coil, and examine the many index points as an current limit element, such as current limit characteristic, the tendency of resistance occurrence, response time, the temperature trend for stability.

The basic performance of the ground system is evaluated as the ground resistance by applying low frequency current below 1 kHz. However, characteristics of the ground system should be analyzed by high frequency current up to 1 MHz since transient currents having a few hundred kHz component flow during a line-to-ground fault and/or a lightning strike. This paper deals with the design and fabrication of a wideband ground impedance meter (WGIM) which measures the impedance of ground systems in ranges from 65 Hz to 1.28 MHz. Also, a noise elimination algorithm using a digital bandpass filter is proposed. The maximum error of the WGIM is 4.91% in the measurement frequency range.

This paper describes the characteristics of electromagnetic wave propagation wave propagation in power transformer. A transformer which is similar which is similar to 154 kV single phase on-site transformer unit was provided for the purpose of the experiment. The 12dieletric windows on the transformer enclosure to install UHF(ultra high frequency) sensors and the full scale mock ups of winding and the core were also euipped in the transformer. Every sensors to be installed to the transformer was tested and verified whether they show same characteristics or not beforethe experiment. A discharge gap which was used as a PD (partial discharge) source moved to or not before the experiment. A discharge gap which was used as a PD (partial discharge) source moved to several necessary locations in the transformer to simulate dielectrie defects. Propagation times of electromagnetic wave signal from PD source to sensors decided by the routes of both reflection phenomenon and diffraction phenomenon were compared each other. The experimental results showed propagation route of the PD signal makes an effect on the frequency spectrum of front part of the signal and the magnitude of the signal and propagation time of the signal when the signal is captured on the sensor

In this paper, we studied the dielectric breakdown voltage characteristics by the AC withstand voltage test on using green insulation dry air instead of SF6 insulation gas used in the GIB (gas insulated bus) of 362 kV GIS (gas insulated switchgear). The AC withstand voltage test applied to the standard KEPCO`s 362 kV GIB with dry air insulation, and the equivalence of dielectric breakdown voltage for dry air and SF6 gas were examined, and the empirical formulas of dielectric breakdown voltage for dry air were calculated, and the criterion of AC withstand voltage test for dry air insulation was derived. Using the criterion, dry air can be used instead of SF6 gas for 362 kV GIB in the factory acceptance test was confirmed.

Frequency domain measurement of propagation loss for ultra high frequency (UHF) partial discharge in the winding of power transformer using a spectrum analyzer and pulse generator is presented. We compared the performance of the method using a network analyzer with and without a winding. Using a network analyzer simplifies the measurement and offers better dynamic range and frequency range. It also provides precise propagation loss within the winding in frequency domain at UHF range. We applied this method to measure UHF propagation loss of transformer mock-up, modeled 154 kV 20 MVA power in KEPCO substation.

Porous carbon electrodes with wooden materials are manufactured by molding carbonized wood powder. Electrical properties of the interface for electrolyte and porous carbon electrode are investigated from viewpoint of NaCl electrolyte concentration, capacitance and complex impedance. Density of porous carbon materials is 0.47∼0.61 g/cm3. NaCl electrolytic absorptance of the porous carbon materials is 5∼ 30%. As the electrolyte concentration increased, capacitance is increased and electric resistance is decrease with electric double layer effect of the interface. The electric current of the porous carbon electrode compared in the copper and the high density carbon electrode was improved on a large scale, due to a increase in surface area. The circuit current increased as the distance between of the porous carbon electrode and the zinc electrode decreased, due to increase in electric field. Experimental results indicated that the current properties of galvanic cell could be improved by using porous carbon electrode.

In this study, we intended to design the optimal Fermi filter to apply the k-space date that is knee image of the rheumatoid arthritis patient acquired from the MRI (magnetic resonance imaging) instrument. After deciding the suitable coefficient for the Fermi filter, the results were compared with modified Fermi filter and inverse Chebyshev filter, Chebyshev filter, Elliptic filter and Butterworth filter. Firstly, in comparison to the results, the radiologist confirmed that modified Fermi filter was best decision for boundary of the rheumatoid arthritis images. The number of the black voxels of the histogram showed the quantity of the results. At the proposed filter images, numbers of the blacks voxels were statistically decreased. That meant voxels only appeared the black color were changed to others voxels color. Because the number of the total voxels was fixed, the area appeared block color could be effected to the other areas. If the modified Fermi filter were used for rheumatoid arthritis patient, the result will be better than other filters.

This study examined the effect of the scattering dose on the thyroid during a mammography examination. One hundred subjects for a mammography examination were enrolled in this study. The average glandular dose (AGD) and thyroid scattering dose (TSD) were measured. Statistical analysis was carried out using the percentage, t-test and co-variance. The mean radiation exposure to the breast and thyroid was 1.08 ± 0.16 and 0.14 ± 0.04 mGy, respectively. The percentage TSD to the AGD was 31.19%. There was no difference between the Rt. and Lt., and CC to MLO, and radiation dose to the TSD was 13.78% of the breast. Therefore, the volume of radiation exposure to the thyroid was 54.12% in a single routine mammography examination. These results suggest that the TSD was increased by increasing radiation dose to the breast. A thyroid protector is considered necessary to decrease the level of radiation exposure.