• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.220-221
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• 2007

금속 촉매 성장 (Metal-induced growth) 를 이용하여, 마이크로 사이즈의 결정질 (Microcrystalline) 박막 실리콘 (Silicon, Si)을 성장하였다. 금속 촉매로서는 코발트, 니켈, 코발트/니켈 복합물질(Co, Ni, or Co/Ni) 이 사용되었으며, 실리콘과 반응하여 실리사이드 (Silicide) 층을 형성한다. 이러한 실리사이드 층은 실리콘과 격자 거리가 유사하여 (Little lattice mismatch), 그 위에 실리콘 박막을 성장하기 위한 모체 (Template) 가 된다. XRD (X-ray diffraction) 분석을 통하여, 실리사이드 ($CoSi_2$ or $NiSi_2$) 의 형성과 성장된 박막 실리콘의 결정성을 연구하였다. 이러한 박막을 이용하여, 쇼트키 태양전지 (Schottky Solar cell) 에 응용하였다. 코발트/니켈 복합물질을 이용하였을 경우에 10.6mA/$cm^2$ 단락전류를 얻었으며, 이는 코발트만을 이용한 경우보다 10 배만큼 증가하였다. 이러한 실리사이드를 매개로한 박막 실리콘의 성장은 공정상에서의 열부담 (Thermal budget) 을 줄일 수 있으며, 대면적 응용에 큰 가능성을 가지고 있다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.338-338
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• 2007

Photo-conductive properties of CdS films deposited on glass substrates by a reactive sputtering in Ar atmosphere were characterized as a function of working pressure and the film thickness. The XRD measurements of CdS films revealed obvious (002) preferred orientation. In 300nm-thick of films, difference between dark and photo-resistance increases with increasing working pressure within the films. The films at 5 mTorr of working pressure show a dark resistance of approximately $1\;{\times}\;10^6\;{\Omega}/{\square}$ and a photo-resistance of $3\;{\times}\;10^4\;{\Omega}/{\square}$. The decrease dark- and photo-resistance of films as thickness decrease were $1.4\;{\times}\;10^6$ and $3\;{\times}\;10^4\;{\Omega}/{\square}$, respectively. CdS films deposited on glass substrates are considered tobe suitable for photo-conductivity materials in stealth radome applications.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.240-245
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• 2005

In order to implement nano-level accuracy of precision equipments, a nano control system is one of the key components. The control system consists of a controller, actuators and sensors having nano-level resolution. In this paper, application area and technical trend on the nano control system are introduced. Some required techniques for realizing nano-level resolution of a controller or actuator are presented. Technical innovation of a control system by IT-fusion and its effect are also described. Finally, domestic research activities for development of the IT-based nano control system are introduced.

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.146.2-146.2
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• 2008

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.40-47
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• 2011

Mobile harbor which is a novel concept of ocean transportation to bring the containers from the cargo ship waiting on the ocean away is being focused now. To provide the mobile harbor with the stable loading/unloading condition, it is necessary to develop the oscillation mitigation technologies such as anti-rolling system. Anti-rolling system using AMD(Active Mass Driving) has merits that it can handle the disturbances more actively and mitigate the rolling oscillation faster than other type anti-rolling system. However, rack-and-pinion type AMD has problems such as big friction noise from gears and motor, wear and tear, and continuous maintenance. In this paper, novel anti-rolling system using Maglev type AMD for mobile harbor is suggested in order to resolve the problems caused by the friction. This novel anti-rolling system doesn't make any friction because it supports the moving mass by using magnetic levitation force and moves it by using propulsion force from the linear motor. The demo system of the novel anti-rolling system using maglev type AMD has been developed in order to investigate its feasibility. This paper presents the procedures and results of development of this demo system.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.10
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• pp.1131-1140
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• 2011

A new rotary gravure-offset printing unit is constructed by paralleling a gravure plate cylinder, a blanket cylinder and a impression roller. A Muti-Unit Gravure-Offset Printing Press(MUGOP) equipped with a series of the 3 printing units is utilized for roll-to-roll fine printing. Its core technology is precise over-piling printing of fine patterns. The severe problems of 'slurring' and 'doubling' in typical offset printing are unavoidable, which can be eliminated by applying a soft pad-type blanket cylinder and the unique 'true rolling' technique. Nip pressure between the blanket cylinder and the plate cylinder is measured by the constant pressure control system which equipped with load cells attached on the cylinders' axes. The running circumference of the blanket cylinder is increased to reach the same circumference of the plate cylinder as the pressure increasing, so that the specifications of the blanket cylinder is determined by the relationships of its shore hardness, diameter and nip pressure. When a softer blanket is used, a blanket cylinder of smaller diameter could give higher nip pressure. Realization of the true rolling technique on the MUGOP makes multilayer printing possible as well as fine printing in printed electronics.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.468-468
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• 2011

Carbon nanotubes (CNTs) have been considered as one of the promising candidate for next-generation field emitters because of their unique properties, such as high field enhancement factor, good mechanical strength, and excellent chemical stability. So far, a lot of researchers have been interested in field emission properties of CNT itself. However, it is necessary to study proper field emitter shapes, as well as the fundamental properties of CNTs, to apply CNTs to real devices. For example, specific applications, such as x-ray sources, e-beam sources, and microwave amplifiers, need to get a focused electron beam from the field emitters. If we use planar-typed CNT emitters, it will need several focal lenses to reduce a size of electron beam. On the other hand, the point-typed CNT emitters can be an effective way to get a focused electron beam using a simple technique. Here, we introduce a fabrication of CNT fibers with nanoscale point tips which can be used as a point-typed emitter. The emitter made by the CNT fibers showed very low turn-on electric field, high current density, and large enhancement factor. In addition, it showed stable emission current during long operation period. The high performance of CNT point emitter indicated the potential e-beam source candidate for the applications requiring small electron beam size.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.466-466
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• 2011

There have been several methods to fabricate carbon nanotube (CNT) emitters, which include as-grown, spraying, screen-printing, electrophoresis and bonding methods. Unfortunately, these techniques generally suffer from two main problems. One is a weak mechanical adhesion between CNTs and the cathode. The as-grown, spraying and electrophoresis methods show a weak mechanical adhesion between CNTs and the cathodes, which induces CNT emitters pulled out under a high electric field. The other is a severe degradation of the CNT tip due to organic binders used in the fabrication process. The screen-printing method which is widely used to fabricate CNT emitters generally shows a critical degradation of CNT emitters caused by the organic binder. Such kinds of problems induce a short lifetime of the CNT field emitters which may limit their practical applications. Therefore, a robust CNT emitter which has the strong mechanical adhesion and no degradation is still a great challenge. Here, we introduce a simple and effective technique for fabrication of CNT field emitter, namely filtration-taping-transfer method. The CNT emitters fabricated by the filtration-taping-transfer method show the low turn-on electric fields, the high emission current, good uniformity and good stability. The enhanced emission performance of the CNT emitters is mainly attributed to high emission sites on the emitter area, and to good ohmic contact and strong mechanical adhesion between the emitters and cathodes. The CNT emitters using a simple and effective fabrication method can be applied for various field emission applications such as field emission displays, lamps, e-beam sources, and x-ray sources. The detail fabrication process will be covered at the poster.

• Advances in nano research
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• v.9 no.1
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• pp.1-13
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• 2020

In this work, the electrical potential (EP) technique with an artificial neural networks (ANNs) for monitoring of nanostructures are used for the first time. This study employs an expert system to identify size and localize hidden nano-delamination (N.Del) inside layers of nano-pipe (N.P) manufactured from Basalt Fiber Reinforced Polymer (BFRP) laminate composite by using low-cost monitoring method of electrical potential (EP) technique with an artificial neural networks (ANNs), which are combined to decrease detection effort to discern N.Del location/size inside the N.P layers, with high accuracy, simple and low-cost. The dielectric properties of the N.P material are measured before and after N.Del introduced using arrays of electrical contacts and the variation in capacitance values, capacitance change and node potential distribution are analyzed. Using these changes in electrical potential due to N.Del, a finite element (FE) simulation model for N.Del location/size detection is generated by ANSYS and MATLAB, which are combined to simulate sensor characteristic, therefore, FE analyses are employed to make sets of data for the learning of the ANNs. The method is applied for the N.Del monitoring, to minimize the number of FE analysis in order to keep the cost and save the time of the assessment to a minimum. The FE results are in excellent agreement with an ANN and the experimental results available in the literature, thus validating the accuracy and reliability of the proposed technique.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.33-39
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• 2010

The moisture absorption properties such as diffusion coefficient and moisture content ratio of liquid type epoxy resin systems with the filler were investigated. Bisphenol A type and Bisphenol F type epoxy resin, Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these liquid type epoxy encapsulant according to the change of filler size. The temperature of glass transition (Tg) of these epoxy resin systems was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these epoxy resin systems according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these systems were calculated in terms of modified Crank equation based on Ficks' law. An increase of Tg and diffusion coefficient with filler size in these systems can be observed, which are attributed to the increase of free volume with Tg. The change of maximum moisture absorption ratio according to the filler size and filler content cannot be observed; however, the diffusion coefficients of these systems decreased with filler content. The diffusion via free volume is dominant in the epoxy resin systems with low nano-sized filler content; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the liquid type epoxy encapsulant with high nano-sized filler content.