• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.206.1-206.1
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• 2014

최근 전자 장비의 금속 전도성 패턴 제작에 있어서 직접적인 프린트가 가능한 프린팅 기술이 기존의 복잡한 photolithography 를 대체할 기술로 주목 받고 있다. 이와 함께 금속 전도성 패턴 제작에 사용되는 고가의 전도성 물질인 Ag ink 및 paste 를 저가의 Cu ink 및 paste 로 대체하기 위한 연구가 진행되고 있다. 하지만 일반적으로 copper 는 대기 중 에서 쉽게 산화되어 높은 저항을 야기시킨다. 따라서 Cu ink 또는 paste 를 제작할 때 copper nanoparticles 을 유기 용매에 분산하여 inert atmosphere에서 합성하거나 [1] copper ink 또는 paste 를 substrate 에 프린트하여 reduction atmosphere 에서 소성시킨다 [2]. 이번 연구에서 Cu paste 를 유리 기판에 screen printing 하여 혼합가스(질소 95%, 수소 5%)와 질소 가스 분위기에서 소성하여 Cu 전극의 소성 거동과 전기적 특성을 분석하였다. 4-point probe를 통해 소성된 Cu 전극의 저항을 측정하여 전도도를 조사하였으며 Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared(FTIR)를 통해 소성된 Cu 전극의 유기물 분해가 전도도에 미치는 영향을 분석하고 Field Emission Scanning Electron Microscopy (FESEM)과 High Resolution Transmission Electron Microscopy (HRTEM)을 통해 Cu nanoparticles 의 grain growth가 전도도에 미치는 영향을 조사하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.149-150
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• 2006

We describe a novel method of scanning probe nanofabrication using a AFM(atomic force microscopy) tip with assistance of Femtosecond laser pulses to enhance fabrication capability. Illumination of the AFM tip with ultra-short light pulses induces a strong electric field between the tip and the metal surface, which allows removing metal atoms from the surface by means of field evaporation. Quantum simulation reveals that the field evaporation is triggered even en air when the induced electric field reaches the level of a few volts per angstrom, which is low enough to avoid unwanted thermal damages on most metal surfaces. For experimental validation, a Ti: sapphire Femtosecond pulse laser with 10 fs pulse duration at 800 nm center wavelength was used with a tip coated with gold to fabricate nanostructures on a thin film gold surface. Experimental results demonstrate that fine structures with critical dimensions less than ${\sim}10nm$ can be successfully made with precise control of the repetition rate of Femtosecond laser pulses.

• 한국재료학회지
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• 제13권2호
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• pp.88-93
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• 2003

Co/Ti bilayer structure in Co salicide process helps to the improvement of device speed by lowering contact resistance due to the epitaxial growth of $CoSi_2$layers. We investigated the epitaxial growth and interfacial mass transport of $CoSi_2$layers formed from $150 \AA$-Co/Ti structure with two step rapid thermal annealing (RTA). The thicknesses of Ti layers were varied from 20 $\AA$ to 100 $\AA$. After we confirmed the appropriate deposition of Ti film even below $100\AA$-thick, we investigated the cross sectional microstructure, surface roughness, eptiaxial growth, and mass transportation of$ CoSi_2$films formed from various Ti thickness with a cross sectional transmission electron microscopy XTEM), scanning probe microscopy (SPM), X-ray diffractometery (XRD), and Auger electron depth profiling, respectively. We found that all Ti interlayer led to$ CoSi_2$epitaxial growth, while $20 \AA$-thick Ti caused imperfect epitaxy. Ti interlayer also caused Co-Ti-Si compounds on top of $CoSi_2$, which were very hard to remove selectively. Our result implied that we need to employ appropriate Ti thickness to enhance the epitaxial growth as well as to lessen Co-Ti-Si compound formation.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.107.1-107.1
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• 2012

Because of beautiful glossy and color, the value of gold leverage is very high in Europe. For improve the quality of white gold, we performed heat treatment on 14K white gold alloys at various age-hardening conditions. Age-hardening behavior and the related phase transformation changes were studied to elucidate the hardening mechanism of 14K white gold alloys. For solid solution treatment [ST], casted 14K white gold alloy specimens were treated at high temperature ($750^{\circ}C$) during 30 minute, and the specimens dropped to water for quenching immediately. For Age-hardening treatment [AT], the specimens were treated at various temperatures ($250^{\circ}C{\sim}300^{\circ}C$). After the heat treatment, we observed increased hardness from 144 Hv to 214 Hv by Vicker's hardness tester. Variation of the grain size measured by optical microscopy (OM) and scanning electron microscopy (SEM) images. By electron probe micro-analysis (EPMA) mapping analysis, we investigated that irregular particles were changed uniformly. After heat treatment, 14K white gold alloys showed improved hardness and became uniformity of grain size by age-hardening treatment.

• 한국표면공학회지
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• 제39권5호
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• pp.215-222
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• 2006

The passivity behavior of copper anode containing impurities in copper sulfate solution for electrorefining process was studied at several different levels of impurities such as As, Sb, Bi and Pb. The passivity behavior was investigated by electrochemical techniques (galvanostatic, potentiodynamic and cyclic voltammetry tests) and surface analysis (optical microscopy, electron probe microanalysis, scanning electron microscopy). The results were that arsenic, antimony inhibited passivation and bismuth accelerated it and lead containing anode showed different passivity behavior from above anodes. The improved passivity characteristics could be explained by decrease in oxygen content in passivity film which resulted from a reaction among the impurities, oxygen and copper in the anode. The SEM image revealed that arsenic or antimony containing anode exhibited a porous passivity film and bismuth containing anode showed the compact passivity film and lead containing anode had loose passivity film on anode.

• International Journal of Oral Biology
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• 제40권2호
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• pp.103-109
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• 2015

Growing evidence suggests that mitochondrial reactive oxygen species (ROS) are involved in various pain states. This study was performed to investigate whether ROS-induced changes in neuronal excitability in trigeminal subnucleus caudalis are related to ROS generation in mitochondria. Confocal scanning laser microscopy was used to measure ROS-induced fluorescence intensity in live rat trigeminal caudalis slices. The ROS level increased during the perfusion of malate, a mitochondrial substrate, after loading of 2',7'-dichlorofluorescin diacetate ($H_2DCF-DA$), an indicator of the intracellular ROS; the ROS level recovered to the control condition after washout. When pre-treated with phenyl N-tert-butylnitrone (PBN) and 4-hydroxy-2,2,6,6-tetramethylpiperidene-1-oxyl (TEMPOL), malate-induced increase of ROS level was suppressed. To identify the direct relation between elevated ROS levels and mitochondria, we applied the malate after double-loading of $H_2DCF-DA$ and chloromethyl-X-rosamine (CMXRos; MitoTracker Red), which is a mitochondria-specific fluorescent probe. As a result, increase of both intracellular ROS and mitochondrial ROS were observed simultaneously. This study demonstrated that elevated ROS in trigeminal subnucleus caudalis neuron can be induced through mitochondrial-ROS pathway, primarily by the leakage of ROS from the mitochondrial electron transport chain.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.35.1-35.1
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• 2009

Vertically aligned zinc oxide (ZnO) nanorods (NRs) with different surface morphology were grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrate. The films thus prepared were characterized by measuring X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) studies. To study the effect of surface morphology on wettability, the contact angle (CA) of water was measured. It was demonstrated that the CA of the deposited ZnO NRs varied between $104^{\circ}$ and $135^{\circ}$ depending upon the surface morphology. Variable temperature photoluminescence (PL) have employed to probe the exciton recombination in high density and vertically aligned ZnO Nanorod arrays. The low-temperature PL characterizes the dominant near-band-edge excitonic emissions from such nanorod arrays.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.268.2-268.2
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• 2013

Nanogap interdigitated electrodes (NIDEs) can serve as an alternative platform for the biomolecular detection [1]. In this work, the NIDEs were adopted in a simple and sensitive detection of Pneumococcal surface protein A (PspA). The NIDEs were fabricated by the combination of photo and chemical lithography. Photolithographically-defined initial gap of about 200 nm was narrowed down to a few tens of nanometers by surface-initiated growth of the initial electrodes (chemical lithography) [2]. Bare silicon oxide surface between the electrodes was chemically modified to immobilize capturing antibodies and, after exposure to the samples, the device was immersed in a solution containing the probe-antibody-conjugated Au nanoparticles (Au NPs). The conductance change accompanied with the Au NP immobilization was interpreted as the existence of PspA. Detection limit of the measurements and further improvement of the detection efficiency were discussed with the results from I-V analysis, scanning electron microscopy, and atomic force microscopy.

• Journal of Welding and Joining
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• 제17권2호
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• pp.104-111
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• 1999

The interfacial microstructure and bond strength were examined for WC-Co/Cu/SM45C steel join using a nickel-plated copper in vacuum at 1323K for 0.6ks∼3.6ks. After bonding, microstructure in bonding interface was observed by OM(Optical Microscopy), SEM(Scanning Electron Microscopy) and EPMA(Eelectron Probe Micro Analyzer). The oil cooling was carried out at 353K, the cooling rate in air and furnace was 22K/s and 4.4K/s. respectively. It was found that dendritic widths increased with the content of cobalt and bonding times at 1323K. As a whole, bond strength values at the same bonding condition decreased in this order: WC-13wt.%Co/SM45Csteel. WC-8wt.%Co/SM45Csteel and WC-4wt.%Co/SM45Csteel. The bond strength of WC-13wt.%Co/S45C steel joint in oil cooling was 273MPa. This value was greatly higher than those of 125MPa in furnace cooling and 93MPa in air cooling at 1323K for 0.6ks. The bond strength values were found to be closely associated with the content of cobalt in WC-Co and cooling rate.

• 대한금속재료학회지
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• 제48권8호
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• pp.780-789
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• 2010

The aim of this study is to evaluate the microstructure and tensile property of in-situ (TiB+TiC) particulate reinforced titanium matrix composites (TMCs) synthesized by the investment casting process. Boron carbide ($1,500{\mu}m$ and $150{\mu}m$) was added to the titanium matrix during vacuum induction melting, which can provide the in-situ reaction of $5Ti+B_4C{\rightarrow}4TiB+TiC$. 0.94, 1.88 and 3.76 wt% of $B_4C$ were added to the melt. The phases identification of the in-situ synthesized TMCs was examined using scanning electron microscopy, an X-ray diffractometer, an electron probe micro-analyzer and transmission electron microscopy. Tensile properties of TMCs were investigated in accordance with the reinforcement size and volume fraction. The improvement of tensile property of titanium matrix composites was caused by load transfer from the titanium matrix to the reinforcement and by grain refinement of titanium matrix and reinforcements.