• 한국자기학회지
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• 제19권3호
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• pp.94-99
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• 2009

Pulsed Laser Deposition 방법으로 합성된 $La_{0.7}Ca_{0.3}MnO_3$ 박막의 물리적 특성을 증착 조건에 따라 조사하였다. 기존에 알려진 바와는 매우 달리 매우 낮은 산소 분압 ($1.0{\times}10^{-5}$, $1.0{\times}10^{-6}Torr$)에서도 큐리 온도가 높은 박막의 합성이 이루어졌으며 이는 박막의 합성 과정에서 쳄버 내부의 산소 분압보다는 플라즈마 plume의 모양과 그 내부 물질들의 운동에너지가 박막의 질을 결정하는 매우 중요한 요소임을 의미한다. 이러한 양질 박막의 합성 증착 조건을 이용하여 $La_{0.7}Ca_{0.3}MnO_3$ 을 Nb가 도핑된 $SrTiO_3$ 기판위에 증착함으로써 p-n 접합을 제작하였으며 이의 전류-전압곡선이 정류 특성을 보였고 그 모양은 자기장에 의해 바뀔 수 있음을 확인하였다.

• 한국철도학회논문집
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• 제12권2호
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• pp.243-248
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• 2009

고속철도의 전차선로에 사용되는 유리애자는 국내에 적용 사례가 없으며 해외에서도 프랑스를 중심으로 한 정적으로 적용되는 품목으로서 국내 적용시 특성분석을 통한 적합성 평가가 요구된다. 본 논문에서는 2004년 이후 운영데이터를 바탕으로 유리애자의 현장 적합성을 평가하기 위해 전기적, 기계적, 외부적(환경) 요인의 3가지 대항목을 선정하여 분야별로 특성 분석을 수행하여 기초데이터를 축적하고 적합성을 평가하였다.

• 반도체디스플레이기술학회지
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• 제7권1호
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• pp.1-5
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• 2008

In this paper, we fabricated pressure difference type gas flow sensor using only dry etching technology by ICP-RIE(inductive coupled plasma reactive ion etching). The sensor's structure consists of a common shear stress type piezoresistive pressure sensor with an orifice fabricated in the middle of the sensor diaphragm. Generally, structure like diaphragm is fabricated by wet etching technology using TMAH, but we fabricated diaphragm by only dry etching using ICP-RIE. To equalize the thickness of diaphragm we applied insulator($SiO_2$) layer of SOI(Si/$SiO_2$/Si-sub) wafer as delay layer of dry etching. Size of fabricated diaphragm is $1000{\times}1000{\times}7\;{\mu}m^3$ and overall chip $3000{\times}3000{\times}7\;{\mu}m^3$. We measured the variation of output voltage toward the change of gas pressure to analyze characteristics of the fabricated sensor. Sensitivity of fabricated sensor was relatively high as about 1.5mV/V kPa at 1kPa full-scale. Nonlinearity was below 0.5%F.S. Over-pressure range of the fabricated sensor is 100kPa or more.

• 대한전자공학회논문지SD
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• 제39권9호
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• pp.62-71
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• 2002

본 논문에서는 용량형 압력센서의 비선형성 문제를 해결하기 위한 적분형 C-V 변환기를 제안하였다. 이 변환기는 스위치 커패시터 적분기와 스위치 커패시터 차동증폭기로 구성되어 있으며 인가된 압력에 반비례하는 센서용량을 전압으로 변환하여 선형적으로 출력한다. 제안된 적분형 C-V 변환기는 PSPICE 시뮬레이션에서 초기 전극간격의 90%에 해당하는 큰 변위에 대해서 0.01%/FS 이하의 매우 낮은 비선형도와 오프셋 용량 및 기생용량에 둔감한 우수한 특성을 보였다. 또한 센서신호처리의 필수기능인 오프셋 보정 및 이득조정이 적분형 C-V 변환기에서 용이하게 구현됨을 보였다.

• 한국진공학회지
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• 제20권2호
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• pp.146-154
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• 2011

접착테이프 형태의 액체누설 감지 필름 센서와 이를 이용하고 경보 장치를 포함한 감지 시스템을 개발하였다. 액체누설 감지 필름형 테이프 센서는 베이스 필름층, 전도성 라인층, 보호 필름층으로 구성되며, 테이프의 두께 $300{\sim}500{\mu}m$, 폭 3.55 cm, 그리고 단위 테이프의 길이는 200 m이다. 전도성 라인층의 필름에는 3개의 전도선과 1개의 저항선이 있다. 이들은 도전성 은나노 잉크를 전자인쇄방식으로 설치한다. 이들 저항선과 전도선 사이에 액체가 누설되어 전기적으로 상호 통전되면, 두 선사이의 저항변화를 전압의 변화로 계측하여 누설 위치를 감지한다. 물을 포함한 전도성 액체에 대한 누설 위치 감지에서 길이 200 m에서 오차 범위는 ${\pm}1m$ 이내이다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권5호
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• pp.201-205
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• 2003

We synthesized dendrimers containing light switchable units, azobenzene group. And the dendrimer containing 48 pyridinepropanol functional end group, which could form a complex structure with metal ions was synthesized. To apply to the molecular level devices or data storage system using Langmuir-Blodgett(LB) film, we firstly investigated the monolayer behavior using the surface pressure-area($\pi$-A) isotherms at air-water interface. And then the surface pressure shift of monolayer by light irradiation was also measured to the dendrimer with azobezene group. As a result, the monolayer of dendrimer with azobenzene group showed the reversible photo-switching behavior by the isomerization of azobenzene group in their periphery. The samples for electrical measurement were fabricated to two types which were pure dendrimer with pyridinepropanol group and its complexes with $Pt^4+$ ions by LB method. We have studied the electrical properties of the ultra thin dendrimer LB films investigated by the current-voltage(I-V) characteristics of Metal/Dendrimer LB films/Metal(MIM) structure. And we have investigated different results in the surface activity at the air-water interface as well as the electrical properties for the monolayers of pure dendrimer with pyridinevopanol group and its complex with $Pt^4+$ ions. In conclusion, it is demonstrated that the metal ion around dendrimer with pyri야nepropanol group can contribute to make formation of network structure among dendrimers and it result from the change of electrical properties. This results suggest that the dendrimers with azobenzene group and pvridinedropanol group can be applied to high efficient nano-device of molecular level.

• Transactions on Electrical and Electronic Materials
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• 제6권2호
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• pp.73-77
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• 2005

In this study, we investigated response characteristics of liquid crystal display (LCD) with different operating mode of nematic liquid crystals (NLCs) such as 45 $^{circ} twisted nematic (TN), 67.3 $^{circ} TN and electrical controlled birefringence (ECB) on the rubbed polyimide (PI) surface with side chains. The pretilt angles generated on polyimide surfaces of the three kinds of LCD operating modes were about 12 $^{circ} that was higher than those of conventional TN-LCOs. Also, the Electro-optical (EO) performance of these LCOs showed stable condition. Low transmittance of the 45 $^{circ} TN and 67.3 $^{circ} TN cell on the rubbed PI surface were measured by using low cell gap d. The fast response time in ECB cell among the three kinds of LCD operating modes was achieved. Also, thermal ability of fast 90 $^{circ} TN-LCD was investigated. The threshold voltage and the response time of thermal stressed TN-LCOs showed the same performances on no thermal stressed TN-LCOs. There was little change of value in these TN cells. However, the transmittances of TN-LCOs on the rubbed PI surface decreased while increasing thermal stress time. Therefore, the thermal stability of TN-LCD was decreased by the high thermal stress for the long duration.

• 한국전기전자재료학회논문지
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• 제12권1호
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• pp.62-68
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• 1999

Ferroelectric $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$(x=0, 0.1, 0.2, 0.3) thin films were deposited on $Pt/SiO_2/Si$ substrate by MOD(Metalorganic Decomposition) process. Metal carboxylate and metal alkoxide were used as precursors, and 2-methoxyethanol, xylene as solvents. After spin coating, thin films were pre-annealed at $400^{\circ}C$, followed by RTA(Rapid Thermal Annealing) and final annealing at $800^{\circ}C$ in oxygen atmosphere. These procedures were repeated three times to obtain thin films with the thickness of $2000{\AA}$. To enhance the nucleation and growth of layered-perovskite phase, thin films were rapid-thermally annealed above $720^{\circ}C$ in oxygen atmosphere. As RTA temperature increased, fluorite phase was transformed to layered-perovskite phase. And the change of Nb contents affected dielectric / electrical properties and microstructure. The ferroelectric characteristics of $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$ thin film were Pr=8.67 $\mu{C}/cm^2$, Ec=62.4kV/cm and $I_{L}=1.4\times10^{-7}A/cm^2$ at the applied voltage of 5V, respectively.

• 한국세라믹학회지
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• 제43권11호
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• pp.715-723
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• 2006

Perovskite oxide materials are very important for the electronics industry, because they exhibit promising properties. With an interest in the obvious applications, significant effort has been invested in the growth of highly crystalline epitaxial perovskite oxide thin films in our laboratory. And the desired structure of films was formed to achieve excellent properties. $Y_1Ba_2Cu_3O_{7-x}$ (YBCO) superconducting thin films were simultaneously deposited on both sides of 3 inch wafer by inverted cylindrical sputtering. Values of microwave surface resistance R$_2$ (75 K, 145 GHz, 0 T) smaller than 100 m$\Omega$ were reached over the whole area of YBCO thin films by pre-seeded a self-template layer. For implementation of voltage tunable high-quality varactor, A tri-layer structured SrTiO$_3$ (STO) thin films with different tetragonal distortion degree was prepared in order to simultaneously achieve a large relative capacitance change and a small dielectric loss. Highly a-axis textured $Ba_{0.65}Sr_{0.35}TiO_3$ (BST65/35) thin films was grown on Pt/Ti/SiO$_2$/Si substrate for monolithic bolometers by introducing $Ba_{0.65}Sr_{0.35}RuO_3$ (BSR65/35) thin films as buffer layer. With the buffer layer, the leakage current density of BST65/35 thin films were greatly reduced, and the pyroelectric coefficient of $7.6\times10_{-7}$ C $cm^{-2}$ $K^{-1}$ was achieved at 6 V/$\mu$m bias and room temperature.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.141-144
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• 2015

The superconducting fault current limiter (SFCL) is an electric power device that limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve the stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its cooling test results are reported. This cooling system uses a Stirling-type cooler to make sub-cooled liquid nitrogen ($LN_2$), which cools the superconductor modules of the SFCL. The $LN_2$ is circulated between the cooler and the cryostat that contains superconductor modules. The $LN_2$ also plays the role of a high voltage insulator between the modules and the cryostat, so the pressure was maintained at 5 bars for high insulation performance. After installation in a test site, the cooling characteristics of the system were tested. In this operation test, some important data were measured such as temperature distribution in $LN_2$, pressure change, performance of the heat exchanger, and cooling capacity of the total system. Consequently, the results indicate that the cooling system operates well as designed.