• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.278-278
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• 2012

최근 폴리이미드(Polyimide) 고분자 물질을 기판으로 하는 플렉시블 전자소자 구현에 관한 연구가 활발히 진행 되고 있다. 폴리이미드는 수분 흡수율이 1% 이하인 소수성 물질로서 폴리이미드 기판 위 전극 형성에 있어 전극 물질이 분리되는 현상이 발생하게 된다. 따라서 본 연구에서는 소수성의 표면 성질을 갖는 폴리이미드 기판의 Asher 처리를 통한 표면 최적화에 대한 실험을 진행하였다. 유리기판 위에 액상 폴리이미드를 ${\sim}10{\mu}m$ 두께로 Spin coating 한 후 $120^{\circ}C$ hot plate에서의 soft bake와 $200^{\circ}C$, $320^{\circ}C$의 furnace에서의 단계적 cure 과정을 통해 표면의 defect을 최소화하였다. Microwave Asher 장비를 이용하여 폴리이미드 막에 10초, 15초, 20초 동안 asher 처리를 한 후 Atomic Force Microscopy (AFM) 장비로 시간에 따른 폴리이미드 기판 표면의 변화를 확인하였다. AFM 확인 결과 10 초의 공정 조건에서 가장 우수한 표면 morphology를 보였으며, 이는 표면의 탄소와 이물질을 제거하기 위해 사용되는 asher 처리 시간이 상대적으로 증가함에 따라 폴리이미드 막의 탄소 성분이 제거 되면서 표면의 형상이 최적화 이상으로 변화하기 때문이다. 본 실험은 폴리이미드를 기반으로 하는 플렉시블 전자소자 구현에 있어 전극 및 소자 제작에 크게 기여할 것으로 판단된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.8
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• pp.732-736
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• 2006

This paper describes the physical characterizations of polycrystalline 3C-SiC thin films heteroepitaxially grown on Si wafers with thermal oxide, In this work, the 3C-SiC film was deposited by LPCVD (low pressure chemical vapor deposition) method using single precursor 1, 3-disilabutane $(DSB:\;H_3Si-CH_2-SiH_2-CH_3)\;at\;850^{\circ}C$. The crystallinity of the 3C-SiC thin film was analyzed by XPS (X-ray photoelectron spectroscopy), XRD (X-ray diffraction) and FT-IR (fourier transform-infrared spectometers), respectively. The surface morphology was also observed by AFM (atomic force microscopy) and voids or dislocations between SiC and $SiO_2$ were measured by SEM (scanning electron microscope). Finally, residual strain was investigated by Raman scattering and a peak of the energy level was less than other type SiC films, From these results, the grown poly 3C-SiC thin film is very good crystalline quality, surface like mirror, and low defect and strain. Therefore, the polycrystalline 3C-SiC is suitable for harsh environment MEMS (Micro-Electro-Mechanical-Systems) applications.

• Electrical & Electronic Materials
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• v.9 no.4
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• pp.364-371
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• 1996

In this study, in order to investigate the applicability of IPN structure to epoxy resin which has been widely used as electrical and electronic insulating materials, DC dielectric breakdown properties and morphology were compared and analyzed according to variation of network structure, using the single network structure specimen formed of epoxy resin alone, interpenetrating polymer network specimen formed of epoxy resin/methacrylic acid resin, and interpenetrating polymer network specimen formed of epoxy resin/methacrylic acid resin/polyurethane resin. As results of the measunnent of DC dielectric breakdown strength at 50[.deg. C] and 130[>$^{\circ}C$], IPN specimen formed of epoxn, resin 100[phr] and methacrylic acid resin 35[phr] was the most excellent, and which corresponded to the SEM phenomena. The effect of IPN was more remarkable at high temperature region than at low temperature region. It is supposed that the defect of epoxy resin, dielectric breakdown strength is lowered remarkably at high temperature region, be complemented according to introducing IPN method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.2
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• pp.156-161
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• 2007

This paper describes the characteristics of polycrystalline ${\beta}$ or 3C (cubic)-SiC (silicon carbide) thin films heteroepitaxailly grown on Si wafers with thermal oxide. In this work, the poly 3C-SiC film was deposited by APCVD (atmospheric pressure chemical vapor deposition) method using HMDS (hexamethyildisilane: $Si_{2}(CH_{3}_{6})$ single precursor. The deposition was performed under various conditions to determine the optimized growth conditions. The crystallinity of the 3C-SiC thin film was analyzed by XPS (X-ray photoelectron spectroscopy), XRD (X-ray diffraction) and FT-IR (fourier transform-infrared spectometers), respectively. The surface morphology was also observed by AFM (atomic force microscopy) and voids or dislocations between SiC and $SiO_{2}$ were measured by SEM (scanning electron microscope). Finally, depth profiling was invesigated by GDS (glow discharge spectrometer) for component ratios analysis of Si and C according to the grown 3C-SiC film thickness. From these results, the grown poly 3C-SiC thin film is very good crystalline quality, surface like mirror and low defect. Therfore, the poly 3C-SiC thin film is suitable for extreme environment, Bio and RF MEMS applications in conjunction with Si micromaching.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.587-587
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• 2013

ZnS is well-known direct band gap II-VI semiconductor, and it attracts intense interest due to its excellent properties of luminescence which enable ZnS to have promising materials for optical, photonic and electronic devices. Especially, the emission wavelength of ZnS falls in the UV absorption band of most organic compoundsand biomolecules, thus it is envisaged that ZnS based devices may find applications in increasingly important fluorescence sensing. We have developed a facile and effective one-step process for the fabrication of single-crystalline and pure-wurtzite ZnS nanostructures possessing sharp band-edge emission at room-temperature having diverse length-to-width ratios. Each of nanostructures was composed of chemically pure, structurally uniform, single-crystalline, and defect-free ZnS. These features not only suppress trap or surface states emission centered at 420 nm, but also enhance UV band-edge emission centered at 327 nm, which give as-synthesized our ZnS nanostructures possible sharp UV emission at room temperature. The reaction medium consisting of mixed solvents such as hydrazine, ethylenediamine, and water as well as proper reaction time and temperature have played an important role in the crystallinity and optical properties of ZnS nanostructures. As-synthesized our ZnS nanostructures possessing sharp UV emission guarantee high potential for both fundamental research and technological applications.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.99-104
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• 2011

In this paper the approach of neural network was proposed which detects a variety of defects in the molded parts. In an attempt to improve the response of the system, It is designed to minimize the use of memory via LookUp table in software. The goal of these methods was to extract the features of samples in learning of neural networks, overcoming the algorithms of defects detection and classification. Through the learning of 500 sample patterns of molded parts, defects of 3% molded parts was detected and classified as the incorrect diameter parts. We expect that proposed approach is an effective alternative to save test time and cost for defect detection of a fine pattern within the molded parts.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.192-194
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• 2003

Since the details in quasi-homogeneous region will be destroyed from the conventional global image enhancement method such as histogram equalization. This defect is caused by the saturation of gray level in equalization process. So the local histogram equalization for each quasi-homogeneous region will be used in order to improve the details in the region itself. To obtain the quasi- homogeneous regions, the original image must be segmented. Here we applied the watershed transform to the interesting image. Since the watershed transform is based on mathematical morphology, therefore, the regions touch can be effectively separated. Hence two adjacent regions which have the similar gray pixels will be split off. The process will be independently applied to three different spectral images. Then three different colors are assigned to each processed image in order to produce a color composite image. By the proposed algorithm, the result image shows the better perception on image details. Therefore, the high efficiency of image classification can be obtained by using this color image.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.401-406
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• 2018

We investigated the effect of ZnO seed layer thickness on the density of ZnO nanorod arrays. ZnO has been deposited using two distinct processes consisting of the seed layer deposition using ALD and subsequent hydrothermal ZnO growth. Due to the coexistence of the growth and dissociation during ZnO hydrothermal growth process on the seed layer, the thickness of seed layer plays a critical role in determining the nanorod growth and morphology. The optimized thickness resulted in the regular ZnO nanorod growth. Moreover, the introduction of ALD to form the seed layer facilitates the growth of the nanorods on ultrathin seed layer and enables the densification of nanorods with a narrow change in the seed layer thickness. This study demonstrates that ALD technique can produce densely packed, virtually defect-free, and highly uniform seed layers and two distinctive processes may form ZnO as the final product via the initial nucleation step consisting of the reaction between $Zn^{2+}$ ions from respective zinc precursors and $OH^-$ ions from $H_2O$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.15-24
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• 2021

In this paper, to analyze the types of surface morphology error according to factors that cause machining error, the experiments were conducted in the ultra-precision diamond machine using a diamond tool. The factors causing machining error were classified into the pressure variation of compressed air, external shock, tool errors, machining conditions (rotational speed and feed rate), tool wear, and vibration. The pressure variation of compressed air causes a form accuracy error with waviness. An external shock causes a ring-shaped surface defect. The installed diamond tool for machining often has height error, feed-direction position error, and radius size error. The types of form accuracy error according to the tool's errors were analyzed by CAD simulation. The surface roughness is dependent on the tool radius, rotational speed, and feed rate. It was confirmed that the surface roughness was significantly affected by tool wear and vibration, and the surface roughness of Rz 0.0105 ㎛ was achieved.

• Korean Journal of Materials Research
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• v.32 no.5
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• pp.249-257
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• 2022

Transparent thin films of pure and nickel-doped ZrO₂ are grown successfully by sol-gel dip-coating technique. The structural and optical properties according to the different annealing temperatures (300 ℃, 400 ℃ and 500 ℃) are investigated. Analysis of crystallographic properties through X-ray diffraction pattern reveals an increase in crystallite size due to increase in crystallinity with temperature. All fabricated thin films are highly-oriented along (101) planes, which enhances the increase in nickel doping. Scanning electron microscopy and energy dispersive spectroscopy are employed to confirm the homogeneity in surface morphology as well as the doping configuration of films. The extinction coefficient is found to be on the order of 10^-2, showing the surface smoothness of deposited thin films. UV-visible spectroscopy reveals a decrease in the optical band gap with the increase in annealing temperature due to the increase in crystallite size. The variation in Urbach energy and defect density with doping and the change in annealing temperature are also studied.