• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.89-89
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• 2009

높은 소수반송자 수명(life-time)을 가지는 고품위 실리콘 기판은 고효율 실리콘 이종접합 태양전지 제작을 위한 중요 요소 기술 중 하나이다. 본 연구에서는 n-type c-Si 기판을 이용한 고효율 실리콘 이종접합 태양전지제작을 위해 hot water oxidation(HWO) 공정을 이용하여 고품위 실리콘 기판을 제작하였다. 실리콘 기판의 특성 분석은 Qusi-steady state photoconductance (QSSPC)를 이용하여 소수반송자 수명을 측정하였으며, 기판의 면저항 및 wetting angle을 측정하여 공정에 따른 특성변화를 분석하였다. Saw damage etching 된 기판을 웨이퍼 표면으로부터 particle, 금속 불순물, 유기물 등의 오염을 제거하기 위해 $60{\sim}85^{\circ}C$로 가열된 Ammonia수, 과산화수소수($NH_4OH/H_2O_2/H_2O$), 염산 과산화수소수($HCL/H_2O_2/H_2O$) 및 실온 희석불산(DHF) 중에 기판을 각각 10분 정도씩 침적하여, 각각의 약액 처리 후에 매회 10분 정도씩 순수(DI water)에서 rinse하여 RCA 세정을 진행한 후 HWO 공정을 통해 기판 표면에 얇은 산화막 을 형성시켜 패시베이션 해주었다. HF를 이용하여 자연산화막을 제거시 HWO 공정을 거친 기판은 매끄러운 표면과 패시베이션 영향으로 기판의 소수 반송자 수명이 증가하며, 태양전지 제작시 접촉저항을 감소시켜 효율을 증가 시킬수 있다. HWO 공정은 반응조 안의 DI water 온도와 반응 시간에 따라 life-time을 측정하여 진행하였으며, 이후 PE-CVD법으로 증착된 a-Si:H layer 및 투명전도 산화막, 금속전극을 증착하여 실리콘 이종접합 태양전지를 제작하였다.

• Composites Research
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• 제34권3호
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• pp.148-154
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• 2021

Carbon/epoxy composite bipolar plate (BP) is a BP that is likely to replace existing graphite bipolar plate of vanadium redox flow cell (VRFB) due to its high mechanical properties and productivity. Multi-functional carbon/epoxy composite BP requires graphite coating or additional surface treatment to reduce interfacial contact resistance (ICR). However, the expanded graphite coating has the disadvantage of having low durability under VRFB operating conditions, and the surface treatments incur additional costs. In this work, an excessive resin absorption method is developed, which uniformly removes the resin rich area on the surface of the BP to expose carbon fibers by applying polyester fabric. This method not only reduces ICR by exposing carbon fibers to BP surfaces, but also forms a unique ditch pattern that can effectively hold carbon felt electrodes in place. The acidic environmental durability, mechanical properties, and gas permeability of the developed carbon/epoxy composite BP are experimentally verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제15권7호
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• pp.4665-4674
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• 2014

The aim of this study was to confirm the feasibility of the electro-coagulation process as a pre-treatment for the membrane separation of anaerobic digestion effluents to minimize membrane fouling. The reduction of membrane fouling was evaluated according to the number of electrodes (immersed surface area of electrodes), current density and contact time. In the case of the small surface area of electrodes, the increased electric field strength resulted in a soluble COD increase due to the destruction of the microbial flocs and/or cells, whereas large changes in the soluble COD were not observed in the case of the high surface area of electrodes. On the other hand, the T-P concentration decreased as a result of the precipitation of aluminum ions and phosphates. The membrane permeation flux increased and the fouling resistance (Rc+Rf) decreased with increasing electric current density. Although the particle size of the anaerobic digestion effluent increased slightly, it was not related directly to the reduced fouling phenomena. The main mechanism for the enhanced flux was attributed to the inorganic particulate produced during electrocoagulation, such as $AlPO_4$, which acted as a dynamic membrane deposited on the membrane surface.

• Journal of the Korean Society for Precision Engineering
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• 제31권10호
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• pp.881-887
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• 2014

Micro-sized Peltier coolers are generally employed for uniformly distributing heat generated in the multi-chip packages. These coolers are commonly classified into vertical and planar devices, depending on the heat flow direction and the arrangement of thermoelectric materials on the used substrate. Owing to the strong need for evaluation of performance of thermoelectric modules, at present an establishment of proper theoretical model has been highly required. The design theory for micro-sized thermoelectric cooler should be considered with contact resistance. Cooling performance of these modules was significantly affected by their contact resistance such as electrical and thermal junction. In this paper, we introduce the useful and optimal design model of small dimension thermoelectric module.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제23권1호
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• pp.92-99
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• 2009

Deeply-driven ground rod in the rainy season may contact with rainwater and ground water. When surge voltages are applied to the submerged ground rods, the ionization around the ground rods are occurred. Ionization in soil and/or water is affected in dynamic performance of ground rod systems. This work aims at studying the transient performance of ground rod system under impulse voltage using scale model in an electrolytic tank. The potential reduction and energy dispersion caused by ionization were treasured and quantitatively analyzed using the Matlab Program. As a result, the peak voltage at the terminal of ground rod was varied with water resistivity and charging voltage of Marx generator. The potential at the terminal of the ground rod was approximately reduced to a half of the applied voltage just below breakdown voltage. Also the energy more than half of the applied energy was dispersed through the ground rod due to ionization just below breakdown voltage.

• Korean Journal of Materials Research
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• 제5권8호
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• pp.929-935
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• 1995

In order to develop COG (Chip On Glass) technology for LCD module interconnecting the driver IC to Al pad electrode on the glass substrate, Anisotropic Conductive Adhesive(ACA) process, the most promising one among COG technologies, was investigated. ACA process was carried out by two steps, dispensing of ACA resin in the bonding area and curing by W radiation. Load on the chip was ranged from 2.0 to 15kg and the chip was heated at about 12$0^{\circ}C$. In resin, the density of conductive particles coated with Au or Ni at the surface were 500, 1000, 2000 and 4000 particles/$\textrm{mm}^2$, and the diameter of particles were 5, 7 and 12${\mu}{\textrm}{m}$. As a result of the experiments, ACA process using ACA particle of diameter and density of 5${\mu}{\textrm}{m}$ and 4000 particles/$\textrm{mm}^2$ respectively shows optimum characteristic with the stabilzed bonding properties and contact resistance.

• Journal of the Microelectronics and Packaging Society
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• 제17권1호
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• pp.19-24
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• 2010

The effects of $O_2$ plasma pretreatment on the properties of Ga-doped ZnO films on PET substrate were studied. GZO films were fabricated by RF magnetron sputtering process. To improve surface energy and adhesion between the PET substrate and the GZO film, $O_2$ plasma pretreatment process was used prior to GZO sputtering. As the RF power and the treatment time increased, the crystallinity increased and the contact angle decreased significantly. When the RF power was 100 W and the treatment time was 600 sec in $O_2$ plasma pretreatment process, the resistivity of GZO films on the PET substrate was $1.90{\times}10^{-3}{\Omega}-cm$.

• Current Photovoltaic Research
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• 제9권4호
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• pp.128-132
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• 2021

Advances in screen printing technology have been led to development of high efficiency silicon solar cells. As a post PERx structure, an n-type wafer-based rear side TOPCon structure has been actively researched for further open-circuit voltage (Voc) improvement. In the case of the metal contact of the TOPCon structure, the poly-Si thickness is very important because the passivation of the substrate will be degraded when the metal paste penetrates until substrate. However, the thin poly-Si layer has advantages in terms of current density due to reduction of parasitic absorption. Therefore, poly-Si thickness and firing temperature must be considered to optimize the metal contact of the TOPCon structure. In this paper, we varied poly-Si thickness and firing peak temperature to evaluate metal induced recombination (Jom) and contact resistivity. Jom was evaluated by using PL imaging technique which does not require both side metal contact. As a results, we realized that the SiN_x deposition conditions can affect the metal contact of the TOPCon structure.

• Composites Research
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• 제19권2호
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• pp.28-34
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• 2006

[ $Cu-TiB_2$ ] metal matrix composites with various weight fractions of $TiB_2$ were fabricated by combination of manufacturing process, SPS (self-propagating high-temperature synthesis) and SPS (spark plasma sintering). The feasibility of $Cu-TiB_2$ composites for welding electrodes and sliding contact material was investigated through experiments on the tensile properties, hardness and wear resistance. To obtain desired properties of composites, composites are designed according to reinforcement's shape, size and volume fraction. Thus proper modeling is essential to predict the effective material properties. The elastic moduli of composites obtained by FEM and tensile test were compared with effective properties from the original Eshelby model, Eshelby model with Mori-Tanaka theory and rule-of-mixture. FEM result showed almost the same value as the experimental modulus and it was found that Eshelby model with Mori-Tanaka theory predicted effective modulus the best among the models.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.78.2-78.2
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• 2012

최근 PRAM의 집적도 향상 및 3차원 적층에 의한 메모리 용량 향상을 위해 셀 선택 스위치로서 박막형 Ovonic Threshold Switching (OTS) 소자를 적용한 Cross bar 구조의 PRAM이 제안된 바 있다. OTS 소자는 비정질 칼코지나이드를 핵심층으로 하는 2단자 소자로서 고저항의 Off 상태에 특정 값 (문턱스위칭 전압) 이상의 전압을 가해주면 저저항의 On 상태로 바뀌고 다시 특정 값 (유지전압) 이하로 전압을 감소시킴에 따라 고저항의 Off 상태로 복원하는 특성을 갖는다. 셀 선택용 스위치로 적용되기 위해서는 핵심적으로 On-Off 상태간의 가역적인 변화 중에도 재료가 비정질 구조를 안정하게 유지해야 하며 전기적으로는 Off 상탱의 저항이 크고 또한 전류값의 점멸비가 커야 한다. GeSe는 이원계 재료로서 단수한 구성에도 불구하고 OTS 소자가 갖추어야할 기본적인 특성을 가지는 것으로 알려져 있다. 본 연구에서는 GeSe로 구성된 OTS 재료에 경원소인 질소를 첨가하여 비정질 상태의 안정성과 소자특성의 개선 효과를 조사하였다. RF-puttering 시 Ar과 $N_2$의 혼합 Gas를 사용하여 조성이 $Ge_{62}Se_{38}$ ($N_2$ : 3%)인 박막을 제작하여 DSC를 통해 결정화온도(Tx)를 확인하였고, $N_2$ gas의 함유량이 각각 1 %, 2 %, 3 %인 $Ge_{62}Se_{38}$인 박막을 전극의 접촉 부 면적이 $10{\times}10\;{\mu}m^2$인 cross-bar 구조의 소자로 제작하여 Threshold switching voltage ($V_{th}$), Delay time ($t_d$), $I_{on}/I_{off}$ 그리고 Endurance 특성을 평가하였다. DSC 분석 결과 $N_2$ 가 3 % 첨가된 GeSe 박막은 Tx가 $371^{\circ}C$에서 $399^{\circ}C$로 증가되었다. $N_2$가 1% 첨가된 GeSe 소자를 측정한 결과 $V_{th}$의 변화 없는 가운데 $I_{on}/I_{off}$이 약 $2{\times}10^3$에서 $5{\times}10^4$로 향상되었다. Endurance 특성 역시 $10^4$에서 $10^5$번으로 향상되었다. $t_d$의 경우 비정질 상태의 저항 증가로 인해 약 50% 증가되었다. 이러한 $N_2$의 첨가로 인한 비정질 GeSe 박막의 변화 원인에 대한 분석 결과를 소개할 예정이다.