• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.531-534
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• 2004

초전도 coated conductor는 보호층/초전도층/완충층/금속기판의 구조를 가지며 완충층은 다층산화물 박막으로 이루어져 있다. 본 연구에서는 니켈 기판의 원자가 초전도층으로 확산 침투하는 것을 방지하는 YSZ(Yttria Stabilized Zirconia) 박막의 증착방법 및 최적조건에 대하여 소개하고자 한다. 금속타겟을 사용하며 산화반응가스로서 수증기를 사용하는 것을 특징으로 하는 DC reactive sputtering을 이용하여 YSZ를 증착하였으며 기판 온도는 $850^{\circ}C$ 이며 증착시 수증기 분압은 1mTorr이었다. YSZ의 최적두께를 알아보기 위하여 $CeO_2(12.2nm)/Ni$ 상부에 130nm, 260nm, 390nm, 650nm로 두께를 달리하여 YSZ층을 증착하고 SEM으로 박막 표면상태를 관찰한 결과 columnar grain growth를 하며 두께가 두꺼워 질수록 표면조도가 증가함을 알 수 있었다. 4개의 각 시료위에 thermal evaporation 증착법을 이용하여 $CeO_2$를 18.3nm의 두께로 증착한 후 PLD를 이용하여 YBCO 초전도 박막을 300nm 두께로 증착하였고 77K, 0T에서 임계전류가 각각 0, 6A, 7.5A, 5A로 측정되었다. 이는 YSZ층의 두께가 두꺼워질수록 기판 구성원자의 확산방지역할을 충실히 하는 반면에 표면조도는 증가함을 알 수 있었다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.128-128
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• 2003

Electrochromism (EC) is defined as a phenomenon in which a change in color takes place in the presence of an applied voltage. Because of their low power consumption, high coloration efficiency, EC devices have a variety of potential applications in smart windows, mirror, and optical switching devices. An EC devices generally consist of a transparent conducting layer, electrochromic cathodic and anodic coloring materials and an ion conducting electrolyte. EC has been widely studied in transition metal oxides(e.g., WO$_3$, NiO, V$_2$O$\sub$5/) Among these materials, WO$_3$ is a most interesting material for cathodic coloration materials due to its lush coloration efficiency (CE), large dynamic range, cyclic reversibility, and low cost material. WO$_3$ films have been prepared by a variety of methods including vacuum evaporation, chemical vapor deposition, electrodeposition process, sol-gel synthesis, sputtering, and laser ablation. Sol-gel process is widely used for oxide film at low temperature in atmosphere and requires lower capital investment to deposit large area coating compared to vacuum deposition process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.872-875
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• 2003

Carbon nitride($CN_x$) thin films were deposited on quartz substrates using reactive RF magnetron sputtering system at uarious deposition conditions and investigated dielectric characteristics. Samples for capacitance measurements were of the MIM(Metal-Insulator-Metal) type devices. Aluminum film electrodes were prepared by a vacuum thermal evaporation method before and after the deposition of carbon nitride films. Capacitances were measured by a FLUKE PM6306 RCL Meter at room temperature. Current-voltage(I-V) characteristics and resistivity were measured by a CATS CA-EDA semiconductor test and analyzer. The carbon nitride films showed ${\alpha}-C_3N_4$ and ${\beta}-C_3N_4$ etc. peaks through Raman and FTIR. Observed surface of film and side structure using SEM(Scanning Electron Microscope), and measured thickness of film by ${\alpha}-step$. We can find that the dielectric constant was the lowest value in 50% nitrogen ratio and the resistivity was the highest value in 70% nitrogen ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.142-145
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• 2000

The performance of ac plasma display panels (PDP) is influenced strongly by the surface glow discharge characteristics on the MgO thin films. This paper deals with the surface glow discharge characteristics and some physical properties of MgO thin films prepared by reactive RF planar unbalanced magnetron sputtering in connection with ac PDP. The samples prepared with the dc bias voltage of -10V showed lower discharge voltage and lower erosion rate by ion bombardment than those samples prepared by conventional magnetron sputtering or E-beam evaporation. The main factor that improves the discharge characteristics by bias voltage is considered to be due to the morphology changes or crystal structure of the MgO thin film by ion bombardment during deposition process.

• Progress in Superconductivity and Cryogenics
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• v.16 no.4
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• pp.49-52
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• 2014

REBCO coated conductor (CC) tapes with superior mechanical and electromechanical properties are preferable in applications such as superconducting coils and magnets. The CC tapes should withstand factors that can affect their performance during fabrication and operation of its applications. In coil applications, CC tapes experience different mechanical constraints such as tensile or compressive stresses. Recently, the critical current ($I_c$) degradation of CC tapes used in coil applications due to delamination were already reported. Thermal cycling, coefficient of thermal expansion mismatch among constituent layers, screening current, etc. can induce excessive transverse tensile stresses that might lead to the degradation of $I_c$ in the CC tapes. Also, CC tapes might be subjected to very high magnetic fields that induce strong Lorentz force which possibly affects its performance in coil applications. Hence, investigation on the delamination mechanism of the CC tapes is very important in coiling, cooling, operation and design of prospect applications. In this study, the electromechanical properties of REBCO CC tapes fabricated by reactive co-evaporation by deposition and reaction (RCE-DR) under transversely applied loading were investigated. Delamination strength of the CC tape was determined using the anvil test. The $I_c$ degraded earlier under transverse tensile stress as compared to that under compressive one.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.69-70
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• 2000

There are currently considerable interest in the applications of conjugated polymers, oligomers, and small molecules for thin-film electronic devices. Organic materials have potential advantages to be utilized as semiconductors in field-effect transistors and light-emitting diodes. In this study, pentacene thin-film transistors (TFTs) were fabricated on glass substrate. Aluminums were used for gate electrodes. Silicon dioxide was deposited as a gate insulator by PECVD and patterned by reactive ion etching (R.I.E). Gold was used for the electrodes of source and drain. The active semiconductor pentacene layer was thermally evaporated in vacuum at a pressure of about $10^{-8}$ Torr and a deposition rate $0.3{\AA}/s$. The fabricated devices exhibited the field-effect mobility as large as 0.07 $cm^2/V.s$ and on/off current ratio as larger than $10^7$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.175-175
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• 2008

투명전극으로 사용되고 있는 Indium tin oxide (ITO) 박막은 전기적 전도도와 기판과의 접확성, 화학적 안정성, 광투과율 등의 특성과 함께 우수한 전기 광학적 거동을 보이고 있다. 그러나 ITO는 고가의 재료이기 때문에 대체 투명전극으로 Al을 도핑한 ZnO 박막의 연구가 활발히 진행되고 있다. ZnO:Al 박막은 chemical vapor deposition, reactive magnetron sputtering, electron-beam evaporation, pulsed laser deposition 등의 당양한 방법을 이용하여 증착하였다. 그러나 최근 낮은 온도에서 대면적의 균일성과 우수한 특성 때문에 atomic layer depositon (ALD) 방법을 이용하여 많은 연구가 진행되고 있으며, 이런 투명전극은 태양전지를 위해 연구되어지고 있다. 따라서 본 연구에서는 ALD 방법으로 Al의 도핑 양을 조절하여, ZnO:Al 박막을 제조하여 그 특성을 평가하고, 또한 ZnO TFT를 제작하여 발표하고자 한다. ZnO와 ZnO:Al 박막은 실리콘과 유리 기판 위에 ALD (Lucida-D200, NCD Technology) 장치로 증착하였다. DEZn, TMA, $H_2O$는 ZnO와 ZnO:Al 박막을 증착하기 위한 전구체와 반응가스로 사용하였다. 증착된 박막은 XRD와 HRTEM을 이용하여 결정구조와 미세구조를 분석하였다. AFM과 4-point probe를 이용하여 증착된 박막의 표면 거칠기와 면저항을 관찰하였다. semiconductor parameter 분석기를 이용하여 제작된 ZnO TFT를 평가하였다.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.2
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• pp.93-99
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• 2006

In this paper, we fabricated and evaluated polydimethylsiloxane(PDMS)-based flexible and implantable micro electrodes. The electrode patterning was carried out with the photolithography and chemical etching process after e-beam evaporation of 100 ATi and 1000 A Au. The PDMS substrate was treated by oxygen plasma using reactive ion etching(RIE) system to improve the adhesiveness of PDMS and metal layers. The minimum line width of fabricated micro electrode was 20 $\mu$m. After finished patterning, we did packaging with PDMS and then brought up the electrode's part about 40 $\mu$m with gold electroplating. The Hank's balanced salt solution(HBSS) test was carried out for 6 month for endurance of fabricated micro electrode. We carried out in-vivo test for the evaluation of biocompatibility by implanting electrodes under the ICR mouse skin for 42 days.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2032-2034
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• 2000

The performance of ac plasma display panels (PDP) is influenced strongly by the surface glow discharge characteristics on the MgO thin films. This paper deals with the surface slew discharge characteristics and some physical properties of MgO thin films prepared by reactive RF planar unbalanced magnetron sputtering in connection with ac PDP. The samples prepared with the do bias voltage of -10V showed lower discharge voltage and lower erosion rate by ion bombardment than those samples prepared by conventional magnetron sputtering or E-beam evaporation. The main factor that improves the discharge characteristics by bias voltage is considered to be due to the morphology changes or crystal structure of the MgO thin film by ion bombardment during deposition process.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.186-191
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• 2004

The reactive flowfield of the transverse injecting combustor has been studied using Euler-Lagrange method in order to develop an efficient solution procedure for the understanding of liquid spray combustion in the transverse injecting combustor which has been widely used in ramjets and turbojet afterburners. The unsteady two-dimensional gas-phase equations have been represented in Eulerian coordinates and the liquid-phase equations have been formulated in Lagrangian coordinates. The gas-phase equations based on the conservation of mass, momentum, and energy have been supplemented by combustion. The vaporization model takes into account the transient effects associated with the droplet heating and the liquid-phase internal circulation. The droplet trajectories have been determined by the integration of the Lagrangian equation in the flow field obtained from the separate calculation without considering the iterative effect between liquid and gas phases. The reported droplet trajectories had been found to deviate from the initial conical path toward the flow direction in the very end of its lifetime when the droplet size had become small due to evaporation. The integration scheme has been based on the TEACH algorithm for gas-phase equation, the second order Runge-Kutta method for liquid-phase equations and the linear interpolation between the two coordinate systems. The calculation results has shown that the characteristics of the droplet penetration and recirculation have been strongly influenced by the interaction between gas and liquid phases in such a way that most of the vaporization process has been confined to the wake region of the injector, thereby improving the flame stabilization properties of the flowfield.