• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.53-53
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• 2000

반도체 산업에서 유기물질의 응용에 많은 관심을 나타내고있으며, 그 응용의 예로는 발광 다이오드(light emitting diode)와 박막트랜지스터(thinfilm transistor)가 주를 이루고 있다. 이러한 유기 물질을 이용하면 소자의 제작 공정의 단순화와 제작 가격을 낮출 수 있는 이점을 기대할 수 있다. 본 연구에서는 유리 기판 위에 pentcence 다이오드를 제작하였다. 유리 기판 위에 silicon dioxide를 PECVD으로 성막하였다. 전극으로는 Ohmic contact를 이루기 위해 금(Au)을 사용하였으며 schottky contact을 이루기 위해서 알루미늄(Al), 인듐(In), 크롬(Cr), 은(Ag), 금(Au)을 각각 사용하였다. 소자의 활성 층으로는 pentcene을 가장 단순한 열 증착법으로 성막하였고, 진공도는 10-8Torr를 유지하였으며 성막 속도는 0.3 $\AA$/sec로 성막하였다. 제작된 소자들은 $\alpha$-step, I-V, C-V, AFM, IR등을 이용하여 측정, 분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.182-182
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• 2010

본 연구에서는 Pt 배면전극에 다양한 조건에서의 ZnO를 성장하여 Schottky 구조를 제작, 접합 특성 및 자외선 검출 특성을 연구하였다. $Al_2O_3$ 기판에 Mirror-like하며 고결정성을 갖는 Pt(111) 배면전극을 형성 후, ZnO 박막의 성장 조건에 따른 접합 특성을 확인하기 위하여 기판온도와 산소분압을 각각 $400{\sim}600^{\circ}C$ ($50^{\circ}C$ 단계), 0~60 sccm (15 sccm 단계)로 성장하였다. 이에 따른 구조적 특성변화를 확인하기 위하여 주사전자현미경 및 X선 회절 특성을 분석하였으며, 전류-전압 특성 곡선을 분석을 통하여 최적의 Schottky contact 형성을 위한 ZnO 성장조건을 규명하고자 하였다. $H_2O_2$를 이용한 표면처리와 Rapid Thermal Annealing (RTA)를 이용한 열처리 과정을 통하여 표면 처리 전 후의 전기적 특성과 광학적 특성의 변화를 비교 분석하였다. 또한 Ohmic 접촉으로 상부전극을 형성, ZnO Schottky photodiode 구조를 제작하여 UV-A, B, C 영역에 따른 UV반응 특성을 분석하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.54-64
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• 2021

Electric vehicles use lithium-ion battery packs as the power supply, where the batteries are connected in series or parallel. The temperature control of each battery is essential to ensure a consistent overall temperature. This study focused on reducing ohmic heating caused by batteries to realize a uniform battery temperature. The battery spacing was optimized to improve air cooling, and the tilt angle between the batteries was varied to optimize the internal structure of the batterypack. Simulations were performed to evaluate the effects of these parameters, and the results showed that the optimal scheme effectively achieved a uniform battery temperature under a constant power discharge. These findings can contribute to future research on cooling methods for battery packs.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.5
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• pp.410-416
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• 2021

The initial electrochemical performance of ceramic fuel cell with thin-film electrolyte was evaluated in terms of peak power density ratio, open circuit voltage ratio, and activation/ohmic resistance ratios at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively. The peak power density ratio reduced as ~17% for 40 minutes, which rapidly decreased in the early stage of the performance evaluation but gradually decreased. The open circuit voltage ratio decreased with respect time; however, its time behavior was remarkably different with the reduction behavior of the peak power density ratio. The activation resistance ratio increased as ~15% for 40 minutes, which was almost similar with the time behavior of the peak power density ratio.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.5
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• pp.340-346
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• 2021

The initial electrochemical performance of ceramic fuel cell with thin-film electrolyte fabricated by plasma-enhanced atomic layer deposition method was evaluated in terms of peak power density ratio, open circuit voltage ratio, and activation/ohmic resistance ratios at 500℃. Hydrogen and air were used as anode fuel and cathode fuel, respectively. The peak power density ratio reduced as ~52% for 30 min, which continually decreased as time increased but degradation rate gradually decreased. The open circuit voltage ratio decreased with respect time; however, its behavior was evidently different from the reduction behavior of the peak power density. The activation resistance ratio increased as ~127% for 30 min, which was almost similar with the reduction behavior of the peak power density ratio.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.1
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• pp.50-57
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• 1986

The fabricatoin sequence of GaAs MIS type diode and its electrical characteristics are presented. Used wafers were undoped GaAS wafer adn Te-doped GaAs wafer. Au and AuGe/Ni was used as schottky contact metal and ohmic contact metal respectively. Oxide layer on GaAs surface was formed by water vapor saturated oxide growth technique and dry oxidation technique. In Te-doped GaAs wafer, cutin voltage of MIS type diode was enhanced about 3V comparing with non-oxide layer diode. From light I-V characteristics fill factor of MIS type Te-doped GaAs diode was about 64%, Voc(open circuit voltage) was 0.67V.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.425-431
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• 1996

KT-2 poloidal-field (PF) system is designed to cope the up-down symmetric double-null (DN) and asymmetric single-null (SN) discharges with typical plasma parameters, in which three sets of "design-basis" scenarios - the ohmic heating (OH), the 5MW and the high bootstrap (HIBS) baseline modes - are applied. The power and energy demand for each cases are also deduced. The peak power and the maximum energy requirements for the KT-2 magnet system, incorporating the PF and the toroidal-field (TF) coils, are proven to be 123MW and 1601MJ, respectively when it is driven in DN configuration. The KT-2 PF system is capable of achieving the machine mission of creating a 500kA heated plasma with a current flattop of $\geq$20 seconds.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.749-753
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• 2012

In present work, anode support for micro-tubular SOFC was fabricated with outer diameter of 3 mm and characterized with microstructure, mechanical properties and gas permeability. The microstructure of surface and cross section of a porous anode support were analyzed by using SEM (Scanning Electron Microscope) image. The gas permeability and the mechanical strength of anode support was measured and analysed by using differential pressure at the flow rates of 50, 100, 150 cc/min. and using universal testing machine respectively. The unit cell composed of NiO-YSZ, YSZ, YSZ-LSM/LSM/LSCF was fabricated and operated with reaction temperature and fuel flow rate and showed maximum power density of $1095mW/cm^2$ on the condition of $800^{\circ}C$. The performance of single cell for micro-tubular SOFC increased with the increasing the reaction temperature due to the decrement of ohmic resistance of cell by the increment of the ionic conductivity of electrolyte through the evaluation of electrochemical impedance analysis for single cell with reaction temperature.

• Journal of the Korean Electrochemical Society
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• v.17 no.1
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• pp.37-43
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• 2014

In this study, capacitive deionization (CDI) was introduced for desalination of mining water. Ion-exchange polymer coated carbon electrodes (IEE) were used in CDI to desalt mining water. The CDI performance using the IEE for desalination of mining water was carried out and then was compared with that using general carbon electrodes without ion-exchange polymer coating (GE). Moreover, to investigate the effect of the concentration of influent solutions on CDI performance, the CDI performance using the IEE for desalination of brackish water (NaCl 200 ppm) was also performed and analyzed. As a result, the higher salt removal efficiency, rate and the lower energy consumption in the CDI process using the IEE and mining water were obtained compared with those using the GE and mining water. It is mainly due to higher non-Faradaic current, low ohmic resistance of the influent, overlapping effect of electric double layers in micropore of the electrode. In addition, the CDI process using the IEE and brackish water shows much higher salt removal efficiency and lower salt removal rate than that using the IEE and mining water. This results from the lower concentration (i.e., higher ohmic resistance) and salt amount of the influent.

• Korean Journal of Optics and Photonics
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• v.23 no.2
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• pp.64-70
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• 2012

We analyzed the changes in electrical and optical characteristics of 1 $mm^2$ multiple-quantum-well (MQW) blue LEDs grown on a c-plane sapphire substrate after a stress test. Experiments were performed by injecting 50 mA current for 200 hours to TO-CAN packaged sample chips. We selected the value of injection current for stress through the junction-temperature measurement by using the forward-voltage characteristics of a diode to maintain a sufficiently low junction temperature during the test. The junction temperature at the selected injection current of 50 mA was 308 K. Experiments were performed under the assumption that the average junction temperature of 308 K did not affect the characteristics of the ohmic contact and the GaN-based materials. Before and after the stress test, we measured and analyzed current-voltage, light-current, light distribution on the LED surface, wavelength spectrum and relative external quantum efficiency (EQE). After the stress test, it was observed experimentally that the optical power and the relative EQE decreased. We theoretically investigated and experimentally proved that these phenomena are due to the increased nonradiative recombination rate caused by the increased defect density.