• Korean Journal of Optics and Photonics
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• v.29 no.5
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• pp.215-219
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• 2018

In this paper we show that the localized surface-plasmon resonance of Ag nanoparticles produced by laser dewetting can be effectively utilized for improving the photocurrent and efficiency of a dye-sensitized $TiO_2$ solar cell. An Ag thin film deposited on a conducting glass substrate was dewetted into nanoparticles by a pulsed laser. A dye-sensitized $TiO_2$ solar cell fabricated on this substrate containing the Ag nanoparticles exhibited improved photovoltaic performance, compared to a reference cell. This is attributed to the increased light trapping that arises from the localized surface-plasmon resonance of the dewetted Ag nanoparticles.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.39-47
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• 2003

Cr thin films were deposited on photosensitive polyimide substrates by RF bias sputtering and DC sputtering and the interfaces between Cr thin film and polyimide were observed using TEM. When the polyimide surface was in-situ RF plasma cleaned at the RF power density of 0.13-2.12 $W/cm^2$, increasing of RF power density changed the morphology of polyimide surfaces from round dig to sharp shape, and surface roughness increased by anisotropic etching. The intermixed layer-like interfaces between Cr and polyimide were observed in the RF bias sputtered specimens. This interface seems to be formed due to the RF cleaning effect; the polyimide surface was RF plasma cleaned while RF power was increased to the setting point before Cr deposition.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.3 s.40
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• pp.13-17
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• 2006

Dense and periodic arrays of holes and tungsten none dots were fabricated on silicon oxide and silicon. The holes were approximately 25 nm wide, 40 nm deep, and 60 nm apart. To obtain nano-size patterns, self-assembling resists were used to produce layer of hexagonally ordered parallel cylinders of polymethylmethacrylate(PMMA) in polystyrene(PS) matrix. The PMMA cylinders were degraded and removed with acetic acid rinse to produce a PS mask for pattern transfer. The silicon oxide was removed by fluorine-based reactive ion etching(RIE). Selectively deposited tungsten nano dots were formed inside nano-sized trench by using a low pressure chemical vapor deposition(LPCVD) method. Tungsten nano dot and trenched silicon sizes were 26 nm and 30 nm, respectively.

• Korean Journal of Materials Research
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• v.9 no.8
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• pp.775-781
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• 1999

Palladium thin films of uniform and highly dense microstructure were prepared by the eletroplating method using novel PdCl$_2$-based plating bath. Principal variables taken into account in this study were the plating temperature and the current density. Electroplated Pd films were characterized for Crystalline orientation, morphology and hardness. The optimal temperature and current density were found be $50^{\circ}C$ and 5mA/$\textrm{cm}^2$, repectively. The measured hardness value for the Pd films when prepared under the optimal condition was as high as 600kg/$\textrm{mm}^2$. A correlation study between variables and properties seems to indicate that the hardness was significantly affected by the microstructure, but not by crystallite orientation.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.479-479
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• 2012

유기발광소자는 낮은 구동전압, 저전력, 높은 명암비, 빠른 응답속도, 넓은 시야각 및 높은 박막의 특성을 가지고 있어서 차세대 평판 패널디스플레이 기술로 각광받고 있다. 하지만 청색 유기발광소자는 적색과 녹색 유기발광소자에 비해 낮은 신뢰성, 발광효율 및 색 순도의 문제점을 가지고 있어, 이를 개선하기 위한 연구가 다양하게 연구되고 있다. 청색 유기발광소자의 경우 발광층 내부로 주입되는 정공과 전자의 균형을 조절하기 위해 p-i-n 구조를 사용하거나 이리듐-유기물 합성물과 같은 인광물질의 적용하여 발광효율을 높이는 청색 유기발광소자에 대한 연구가 진행되고 있다. 하지만 정공 보조층과 청색 형광층의 도핑구조의 청색 유기발광소자에 대한 발광효율 증가 메커니즘에 관한 연구는 비교적 많이 이루어지지 않았다. 본 연구에서는 열 증착 방법을 이용하여 정공 보조층과 청색 형광층으로 구성된 이중 발광층을 사용한 청색유기발광소자의 발광효율 증가 메커니즘에 대해 연구하였다. 10%의 2,9-dimethyl-4,7-diphenyl-1,10-phenanthorlene (BCP)로 도핑된 2-methyl-9,10-bis(naphthalene-2-yl)anthracene (MADN)층을 발광층으로 사용한 유기발광소자, 5% MADN으로 도핑된 1, 3-bis(carbazol-9-yl)benzene (mCP) 층을 발광층으로 사용한 소자 및 10% BCP로 도핑 된 MADN 층과 5% MADN로 도핑 된 mCP층을 혼합하여 발광층으로 사용한 소자의 전류밀도-전압-발광 특성을 비교하여 청색 유기발광소자의 발광효율 증가 메커니즘을 분석하였다. 이중 발광층을 가지는 소자는 두 단일 발광층 중심부의 경계면에서 축적된 정공에 의해 발생한 쿨롱 인력으로 더 많은 전자들을 끌어들이게 되어 엑시톤 형성 및 빛 방출이 증가하였다. 이 실험의 결과는 MADN 형광물질을 가진 청색 유기발광소자의 발광효율 증가 메커니즘에 대한 이해를 높이는데 도움을 줄 수 있다.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.409-415
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• 2012

$TiO_2$ thin films for high energy density capacitors were prepared by r.f. magnetron sputtering at room temperature. Flexible PET (Polyethylene terephtalate) substrate was used to maintain the structure of the commercial film capacitors. The effects of deposition pressure on the crystallization and electrical properties of $TiO_2$ films were investigated. The crystal structure of $TiO_2$ films deposited on PET substrate at room temperature was unrelated to deposition pressure and showed an amorphous structure unlike that of films on Si substrate. The grain size and surface roughness of films decreased with increasing deposition pressure due to the difference of mean free path. X-ray photoelectron spectroscopy (XPS) analysis revealed the formation of chemically stable $TiO_2$ films. The dielectric constant of $TiO_2$ films was significantly changed with deposition pressure. $TiO_2$ films deposited at low pressure showed high dissipation factor due to the surface microstructure. The dielectric constant and dissipation factor of films deposited at 70 mTorr were found to be 100~120 and 0.83 at 1 kHz, respectively. The temperature dependence of the capacitance of $TiO_2$ films showed the properties of class I ceramic capacitors. $TiO_2$ films deposited at 10~30 mTorr showed dielectric breakdown at applied voltage of 7 V. However, the films of 500~300 nm thickness deposited at 50 and 70 mTorr showed a leakage current of ${\sim}10^{-8}{\sim}10^{-9}$ A at 100 V.

• Polymer(Korea)
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• v.32 no.1
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• pp.38-42
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• 2008

Ultrathin films were coated on low density Polyethylene (LDPE) food packaging films by plasma polymerization of methane, acetylene, hexamethyldisiloxane (HMDSO), and HMDSO+oxygen to improve the barrier property of the LDPE films. The film coated in HMDSO +oxygen (flow rate: 0.6+ 9.0 SCCM) plasma at 40 W for 10 min showed the highest improvement in the barrier property against oxygen, reducing the permeability of oxygen as much as 18.6 times. The film coated in acetylene (flow rate 0.75 SCCM) plasma at 10 W for 10 min showed the highest improvement in the barrier property against carbon dioxide and moisture, reducing the permeability of carbon dioxide and moisture as much as 12.0 and 3.0 times, respectively. In addition, cherry tomato, cucumber, and mushroom (Flammulina velutipes) wrapped with the coated films were kept fresh $1.5{\sim}3.0$ times longer than those wrapped with an LDPE film.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.4
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• pp.303-310
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• 2017

Pressure retarded osmosis(PRO) has attracted much attention as potential technology to reduce the overall energy consumption for reverse osmosis(RO) desalination. The RO/PRO hybrid process is considered as the most logical next step for future desalination. The PRO process aims to harness the osmotic energy difference of two aqueous solutions separated by a semipermeable membrane. By using the concentrated water(RO brine) discharged from existing RO plants, the PRO process can effectively exploit a greater salinity gradient to reduce the energy cost of processing concentrated water. However, in order to use RO brine as the draw solution, PRO membrane must have high water flux and enough mechanical strength to withstand the high operational pressure. This study investigates the development of a thin film composite PRO membrane and spiral wound module for high power density. Also, the influence of membrane backing layer on the overall power density was studied using the characteristic factors of PRO membranes. Finally, the performance test of an 8-inch spiral wound module was carried out under various operating conditions(i.e. hydraulic pressure, flow rate, temperature). As the flow rate and temperature increased under the same hydraulic pressure, the PRO performance increased due to the growth of water permeability coefficient and osmotic pressure. For a high performance PRO system, in order to optimize the operating conditions, it is highly recommended that the flow pressure be minimized while the flow rate is maintained at a high level.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.520-520
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• 2013

Lateral 구조를 갖는 탄소나노튜브 에미터 캐소드의 금속전극 선폭과 간격은 탄소나노튜브 에미터 밀도와 게이트에 인가되는 전계의 크기에 밀접한 관계가 있어 전계방출특성에 큰 영향을 나타내므로 조속한 상업화를 위해서는 최적화 연구가 요구된다. 따라서 본 연구에서는 금속전극의 선폭과 간격을 110/30, 80/30, 40/30과 120/20, 90/20, 20/20 ${\mu}m$로 각각 변화시켜 4.6인치 탄소나노튜브 에미터 기반 flat light lamp 개발연구를 진행하였다. 이때 사용한 금속전극은 2 mm 두께를 갖는 4.6인치 소다라임 글라스 위에 패턴 된 PR에 Ag를 sputtering하여 증착 후 PR을 lift-off하여 형성하였다. 이와 같이 형성된 금속전극은 ~1 ${\mu}m$와 12 nm의 두께와 표면단차를 각각 가지고 있었다. 형성된 금속전극 위에 유전체와 탄소나노튜브 에미터를 각각의 페이스트를 사용하여 스크린 인쇄와 소성과정을 통해 형성하였다. 이때 레이저 빔을 전극사이의 빈 공간에 조사하여 탄소나노튜브 에미터를 금속전극 위에 정밀하게 정렬하였으며 잔존하는 유기물과 유기용매를 없애기 위해 대기압 공기분위기의 $410^{\circ}C$에서 10분간 소성과정을 거친 후 접착테이프를 사용하여 잔탄 속에 있는 탄소나노튜브 에미터를 물리적 힘으로 수직하게 노출시켜 캐소드를 준비하였다. 애노드는 전계에 의해 방출된 전자의 측정과 전계방출 이미지를 얻기 위해서 P22 형광체와 Al박막이 증착된 2 mm 두께의 소다라임 글라스를 사용하였다. 캐소드와 애노드 사이의 간격은 6~10 mm로 유지하였고, 진공챔버의 기본 압력을 $5{\times}10^{-6}$ Torr 이하로 유지하였다. 캐소드와 게이트 전극에 1, 4 kHz와 3% duty를 갖는 bipolar 형태의 DC 사각펄스파를, 애노드에 ~18 kV의 DC 고전압을 각각 인가하여 평가하였으며 추후, 이렇게 제작된 다양한 선폭과 간격을 갖는 탄소나노튜브 에미터 기반 flat light lamp의 전계방출특성과 효율에 대한 비교 연구를 진행할 계획이다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.86-92
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• 2013

$SF_6/O_2$ inductively coupled plasmas were employed to texture Si surface as a pretreatment for nanocrystalline diamond film growth. It was found that the $SF_6/O_2$ plasma texturing provided a very wide process window where normalized roughness values in the range of 2~16 could be obtained. Significantly improved nucleation densities of ${\sim}6.5{\times}10^{10}cm^{-2}$ compared to conventional mechanical abrasion were achieved after seeding for the textured Si substrate.