• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.189-189
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• 2015

Plasmonics, sensor, field effect transistors, solar cells 등 다양한 적용분야를 가지는 실리콘 구조체는 제작공정에 의해 전기적 및 광학적 특성이 달라지기 때문에 적합한 나노구조 제작방법이 요구되고 있다. 나노구조체 제작방법으로는 Photo lithography, Extreme ultraviolet lithography (EUV), Nano imprinting lithography (NIL), Block copolymer (BCP) 방식의 방법들이 연구되고 있으며, 특히 BCP는 direct self-assembly 특성을 가지고 있으며 가격적인 면에서도 큰 장점을 가진다. 하지만 BCP를 mask로 사용하여 식각공정을 진행할 경우 BCP가 버티지 못하고 변형되어 mask로서의 역할을 하지 못한다. 이러한 문제를 해결하기 위하여 본 논문에서는 BCP와 질화막을 이용한 double mask 방법을 사용하였다. 기판 위에 BCP를 self-assembly 시키고 mask로 사용하여 hole 부분으로 노출된 기판을 Ion gun을 통해 질화 시킨 후에 BCP를 제거한다. 기판 위에 hole 모양의 질화막 표면은 BCP와 다르게 etching 공정 중 변형되지 않는다. 이러한 질화막 표면을 mask로 사용하여 pillar pattern의 실리콘 나노구조체를 제작하였다. 질화막 mask로 사용되는 template은 PS와 PMMA로 구성된 BCP를 사용하였다. 140kg/mol의 polystyrene과 65kg/mol의 PMMA를 톨루엔으로 용해시키고 실리콘 표면 위에 spin coating으로 도포하였다. Spin coat 후 230도에서 40시간 동안 열처리를 진행하여 40nm의 직경을 가진 PS-b-PMMA self-assembled hole morphology를 형성하였다. 질화막 형성 및 etching을 위한 장비로 low-energy Ion beam system을 사용하였다. Reactive Ion beam은 ICP와 3-grid system으로 구성된 Ion gun으로부터 형성된다. Ion gun에 13.56 MHz의 frequency를 갖는 200W 전력을 인가하였다. Plasma로부터 나오는 Ion은 $2{\Phi}$의 직경의 hole을 가지는 3-grid hole로 추출된다. 10~70 voltage 범위의 전위를 plasma source 바로 아래의 1st gird에 인가하고, 플럭스 조절을 위해 -150V의 전위를 2nd grid에 인가한다. 그리고 3rd grid는 접지를 시켰다. chamber내의 질화 및 식각가스 공급은 2mTorr로 유지시켰다. 그리고 기판의 온도는 냉각칠러를 이용하여 -20도로 냉각을 진행하였다. 이와 같은 공정 결과로 100 nm 이상의 높이를 갖는 40 nm직경의 균일한 Silicon pillar pattern을 형성 할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1135-1140
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• 2012

An electrochromatographic microchip with carboxyl-group-derivatized mono-disperse silica packing was prepared from the corresponding colloidal silica solution by utilizing capillary action and self-assembly behavior. The silica beads in water were primed by the capillary action toward the ends of cross-patterned microchannel on a cyclic olefinic copolymer (COC) substrate. Slow evaporation of water at the front of packing promoted the self-assembled packing of the beads. After thermally binding a cover plate on the chip substrate, reservoirs for sample solutions were fabricated at the ends of the microchannel. The packing at the entrances of the microchannel was silver coated to fix utilizing an electroless silver-plating technique to prevent the erosion of the packed structure caused by the sudden switching of a high voltage DC power source. The electrochromatographic behavior of the microchip was explored and compared to that of the microchip with bare silica packing in basic borate buffer. Electrophoretic migration of Rhodamine B was dominant in the microchip with the carboxyl-derivatized silica packing that resulted in a migration approximated twice as fast, while the reversible adsorption was dominant in the bare silica-packed microchip. Not only the faster migration rates of the negatively charged FITC-derivatives of amino acids but also the different migration due to the charge interaction at the packing surface were observed. The electrochromatographic characteristics were studied in detail and compared with those of the bare silica packed microchip in terms of the packing material, the separation potential, pH of the running buffer, and also the separation channel length.

• Membrane and Water Treatment
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• 제9권5호
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• pp.317-325
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• 2018

Polyvinyl chloride (PVC) ultrafiltration (UF) membrane was modified by silica sol in the coagulation bath during non-solvent induced phase separation (NIPS) process. The effects of silica sol concentrations on the morphology, surface property, mechanical strength and separation property of PVC UF membranes were systematically investigated. PVC membranes were characterized by Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), contact angle goniometry and tensile strength measurement. The results showed that silica had been successfully assembled on the surface of PVC UF membrane. With the increase of silica sol concentration in the coagulation bath, the morphologies of PVC UF membranes changed from cavity structure to finger-like pore structure and asymmetric cross-section structure. The hydrophilicity and permeability of PVC UF membranes were further evaluated. When silica sol concentration was 20 wt.%, the modified PVC membrane exhibited the highest hydrophilicity with a static contact angle of $36.5^{\circ}$ and permeability of $91.8(L{\cdot}m^{-2}{\cdot}h^{-1})$. The structure of self-assemble silica had significant impact on the surface property, morphology, mechanical strength and resultant separation performance of the PVC membranes.

• 한국전기전자재료학회논문지
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• 제23권6호
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• pp.502-507
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• 2010

In order to design nano structured materials with enhanced thermoelectric properties, the alloys in the pseudo-binary $Bi_2Te_3$-PbTe system are investigated for their micro structure properties. For this synthesis, the liquid alloys are cooled by the water quenching method. Micro structure images are obtained by using an electron probe micro analyzer(EPMA). Dendritic and lamellar structures are clearly observed with the variation in the composition ratio between $Bi_2Te_3$ and PbTe. The increase in the $Bi_2Te_3$ composition ratio causes to change of the structure from dendritic to lamellar. The Seebeck coefficient of sample 5, in which the mixture rate of $Bi_2Te_3$ is 83%, is measured as the highest value. In contrast, the others decrease with the increase of the $Bi_2Te_3$ composition ratio. Meanwhile, p-type characteristics are observed in sample 6, at 91%-$Bi_2Te_3$ mixture rate. The power factors of the all samples are calculated with the Seebeck coefficient and resistivity.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.438-444
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• 2008

A self-assembled monolayer of 2,2'-bipyridine (22BPY) molecules on Au(111) underwent a structural phase transition when the polarity of a bias voltage was switched in scanning tunneling microscopy (STM) experiments. The nature of two bright spots representing each 22BPY molecule on Au(111) in the high-resolution STM images was identified by calculating the partial density plots for a monolayer of 22BPY molecules adsorbed on Au(111) using tight-binding electronic structure calculations. The stacking pattern of the chains of 22BPY molecules on Au(111) was explained by examining the intermolecular interactions between the 22BPY molecules based on first principles electronic structure calculations for a 22BPY dimer, (22BPY)2. The structural instability of the 22BPY molecule arrangement caused by a change in the bias voltage switch was investigated by estimating the adsorbate-surface interaction energy using a point-charge approximation for Au(111).

• Macromolecular Research
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• 제12권6호
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• pp.598-603
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• 2004

Cellulose nitrate (CN) composite membranes, containing cobalt porphyrin (CoP) complexes self-assembled within nanometer-sized rhenium clusters (ReCoP), have been prepared and their oxygen and nitrogen gas perme­abilities were analyzed. The solubility of ReCoP and the characteristics of the corresponding composite membranes were analyzed using a Cahn microbalance, FT-IR spectroscopy, wide-angle X-ray scattering, and differential scanning calorimetry. The nitrogen permeability through the CN composite membranes decreased upon addition of ReCoP and CoP, which implies that the presence of these oxygen carrier complexes affects the structure of the polymer matrix. The oxygen permeability through the composite membranes containing small quantities of ReCoP decreased, but it increased upon increasing the concentration. The oxygen gas transport was affected by the matrix at low ReCoP concentrations, but higher concentrations of ReCoP increased the oxygen permeability as a result of its reversible and specific interactions with oxygen, effectively realizing ReCoP carrier-mediated oxygen transport.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.186-186
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• 2012

This report investigates a new synthetic route and the size-dependent optical and electrical properties of PbS nanocrystal quantum dots (NQDs) in diameters ranging between 1.5 and 6 nm. Particularly we synthesize ultra-small sized PbS NQDs having extreme quantum confinement with 1.5~2.9 nm in diameter (2.58~1.5 eV in first exciton energy) for the first time by adjusting growth temperature and growth time. In this region, the Stokes shift increases as decreasing size, which is testimony to the highly quantum confinement effect of ultra-small sized PbS NQDs. To find out the electrical properties, we fabricate self-assembled films of PbS NQDs using layer by layer (LBL) spin-coating method and replacing the original ligands with oleic acid to short ligands with 1, 2-ethandithiol (EDT) in the course. The use of capping ligands (EDT) allows us to achieve effective electrical transport in the arrays of solution processed PbS NQDs. These high-quality films apply to Schottky solar cell made in an glass/ITO/PbS/LiF/Al structure and thin-film transistor varying the PbS NQDs diameter 1.5~6 nm. We achieve the highest open-circuit voltage (＜0.6 V) in Schottky solar cell ever using PbS NQDs with first exciton energy 2.58 eV.

• Macromolecular Research
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• 제17권5호
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• pp.301-306
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• 2009

This work has demonstrated that a novel amphiphilic poly(epichlorohydrine)-graft-polystyrene (PECH-g-PS) copolymer at 34:66 wt% was synthesized via atom transfer radical polymerization (ATRP) of styrene using PECH as a macroinitiator. The structure of the graft copolymer was characterized by nuclear magnetic resonance ($^1H$ NMR) and FTIR spectroscopy, demonstrating that the "grafting from" method using ATRP was successful. The self-assembled graft copolymer was used as a template film for the in-situ growth of silver nanoparticles from $AgCF_3SO_3$ precursor under UV irradiation. The in situ formation of silver nanoparticles with 6-8 nm in average size in the solid state template film was confirmed by transmission electron microscopy (TEM), UV-visible spectroscopy and wide angle X-ray scattering (WAXS). Differential scanning calorimetry (DSC) also displayed the selective incorporation and the in situ formation of silver nanoparticles within the hydrophilic PECH domains, probably due to stronger interaction of the silvers with the ether oxygens of PECH backbone than that with hydrophobic PS side chains.

• 한국정밀공학회지
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• 제32권6호
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• pp.577-585
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• 2015

We fabricated multi-scale such as macro-, micro-, and multi-scale wrinkles by using repetitive volume dividing (RVD) method and thermal curing process. Also wrinkle surface was modified with coating of a self-assembled monolayer (SAM). We measured the contact angle of each wrinkled surface, and observed the behavior of droplets on sloping surface. Through experimental study, we found out that the contact angle was much higher in case of multi-scale and SAM coated wrinkles. And micro-scale wrinkle showed a high contact angle comparing with that of macro-scale wrinkle. Dynamic behaviors of a water droplet like sliding velocity on diverse wrinkled surfaces were dependent on their static contact angles. These results showed that hydro-dynamic characteristics were changed depending on the wrinkle structure and the material forming the wrinkle. These dynamic characteristics can be utilized in bio-chip, microfluidics, and many others in order to control easily chemical reactivity.

• Architectural research
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• 제16권1호
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• pp.17-25
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• 2014

This research is to restructure the public assessment of housing management in a standardized fashion, and a self-administered questionnaire survey was employed for data collection and analysis. In doing so, all the assessment tools nationwide were identified and assembled to extract the items included in the survey form. The survey form was mailed out to local officers in charge of housing management and professional housing managers in the nation, and the responses were statistically analyzed in order to structure the standard assessment tool of housing management. This research classified 3 main areas (General Maintenance, Operation and Community Living) in evaluating the housing management performance, and identified 35 essential items and 52 optional items. The 35 essential items were drawn from the 16 categories of the 3 areas (11 items of 5 categories for General Maintenance, 7 items of 4 categories for Operation, and 17 items of 7 categories for Community Living), and the rest 52 optional items were from the 16 categories of the 3 areas (24 items of 7 categories for General Maintenance, 26 items of 7 categories for Operation, and 2 items of 2 categories for Community Living). While all the items in the research are quantifiable, it's suggested that qualitative measurements be complementarily utilized in the assessment not only to explore the best practices of housing management but also to refine and modify the standardized tool in response to various environmental changes. As the public assessment of housing management is context-sensitive and critically related to local housing profile, the continuous implementation of the assessment will facilitate shifting the housing paradigm from production and consumption to management and reproduction.