• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.474-474
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• 2013

PDMS는 미세패턴을 위해 소프트 리소그래피 널리 활용되어질 뿐만 아니라, 재질이 투명하고 탄성과 강한 내구성을 갖고 있어 유연한 광학 및 전자소자에 이용될 수 있다. 최근에는, 이러한 PDMS를 서브파장구조(subwavelength grating structure)를 형성하거나 텍스쳐(texture)표면구조를 이용한 효과적인 반사방지막(antireflection coating)기판을 제작하여 태양전지 및 디스플레이 소자의 성능을 발전시키는 연구가 활발히 진행되고 있다. 한편, 수열합성법(hydrothermal method)이나 전기화학증착법(electrodeposition method)으로 비교적 간단한 공정을 통해서 다양한 기판위에 산화아연(ZnO) 나노막대(nanorod)를 수직정렬로 성장시킬 수 있는데, 이러한 구조는 반사방지특성의 유효 굴절률 분포(effective refractive index profile)를 갖고 있기 때문에 LED나 태양전지에 성능을 개선할 수 있다. 이에 본 연구에서는 수열합성법을 통해 성장된 수직 정렬된 산화아연 나노막대를 이용한 PDMS 표면의 미세패턴 형성하여 광학적 특성을 분석하였다. 실험을 위해, 스퍼터링을 통해서 산화아연 시드층을 형성한 후, 질산아연헥사수화물과 헥사메틸렌테트라민을 수용액에 담가두어 산화아연 나노막대를 성장시켰으며, PDMS의 베이스와 경화제의 질량비를 10：1으로 용액을 준비하여 수직 정렬된 산화아연 나노막대 표면을 casting method으로 코팅하여 열경화 처리하였다. 제작된 샘플의 형태, 구조 광특성을 관찰하기 위해서 전계방출형전자현미경, X선 회절 분석기, 분광 광도계를 이용하였다.

• Journal of the Korean Vacuum Society
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• v.20 no.4
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• pp.276-279
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• 2011

Polymer electrostrictor materials can exhibit high electroactive strain and hold increasing promise for a variety of actuator applications. The size of available actuators has been limited, however, by the solution-based casting and annealing process generally required to prepare electrostrictor actuator materials. We report on a high throughput melt and stretch extrusion process capable of creating large sheets of an electrostructive terpolymer, poly (vinylidene fluoride-trifluoroethylene-1, 1-chlorofluoroethlene) while producing a suitable crystallinity and crystal phase for high strain electrostrictor performance such as artificial muscle systems.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.1
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• pp.59-63
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• 2017

We present a multi-sample array device based on a pneumatic system. Solenoid valves were used to control a micro valve in a pneumatic system. The use of a compressor together with a vacuum pump ensured that one outlet could supply both compression and vacuum pressure. The multi-sample array device was fabricated using conventional photolithography and PDMS casting. The device was composed of a multiplexer, sample array, and rinsing. The multiplexer could control four sample solutions injecting into the sample array chamber. Sample solution not arrayed was removed by DI-water from the rinsing inlet. To prevent trapping of microbubbles in the channel during injection of sample solution into the device, surfactant was added in PDMS solution to serve as a hydrophilic surface treatment. As a result, the device could be used as a sample array for 64 cases, using four samples and three columns of three chambers.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.9-9
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• 2011

There has been strong demand for novel nonvolatile memory technology for low-cost, large-area, and low-power flexible electronics applications. Resistive memories based on metal oxide thin films have been extensively studied for application as next-generation nonvolatile memory devices. However, although the metal oxide-based resistive memories have several advantages, such as good scalability, low-power consumption, and fast switching speed, their application to large-area flexible substrates has been limited due to their material characteristics and necessity of a high-temperature fabrication process. As a promising nonvolatile memory technology for large-area flexible applications, we present a graphene oxide-based memory that can be easily fabricated using a room temperature spin-casting method on flexible substrates and has reliable memory performance in terms of retention and endurance. The microscopic origin of the bipolar resistive switching behaviour was elucidated and is attributed to rupture and formation of conducting filaments at the top amorphous interface layer formed between the graphene oxide film and the top Al metal electrode, via high-resolution transmission electron microscopy and in situ x-ray photoemission spectroscopy. This work provides an important step for developing understanding of the fundamental physics of bipolar resistive switching in graphene oxide films, for the application to future flexible electronics.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.376-376
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• 2011

I-III-VI2 chalcopyrite compounds, particularly copper, indium, gallium selenide(Cu(InxGa1-x)Se2, CIGS), are effective light-absorbing materials in thin-film solar application. They are direct band-gap semiconductors with correspondingly high optical absorption coefficients. Also they are stable under long-term excitation. CIS (CIGS) solar cell reached conversion efficiencies as high as 19.5%. Several methods to prepare CIS (CIGS) absorber films have been reported, such as co-evaporation, sputtering, selenization, and electrodeposition. Until now, co-evaporation is the most successful technique for the preparation of CIS (CIGS) in terms of solar efficiency, but it seems difficult to scale up. CIS solar cells have been hindered by high costs associated with a fabrication process. Therefore, inorganic colloidal ink suitable for a scalable coating process could be a key step in the development of low-cost solar cells. Here, we will present the preparation of CIS photo absorption layer by a solution process using novel metal precursors. Chalcopyrite copper indium diselenide (CuInSe2) nanocrystals ranging from 5 to 20nm in diameter were synthesized by arrested precipitation in solution. For the fabrication of CIS photo absorption layer, the CuInSe2 colloidal ink was prepared by dispersing in organic solvent and used to drop-casting on molybdenum substrate. We have characterized the nanoparticless and CIS layer by XRD, SEM, TEM, and ICP.

• Journal of Information Display
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• v.6 no.4
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• pp.1-5
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• 2005

Perylene-based pyrrolopyrone derivative (PPD) was synthesized via condensation reaction with perylenetetracarboxylic dianhydride and 1,2-phenylenediarnine as n-type channel material. The structure of PPD was characterized by spectroscopic methods such FT-IR and $^1H$-NMR. PPD exhibited high thermal stability ($T_{d5wt%}: 560^{\circ}C$) and was found to be soluble only in protonic solvents with high acidity such as methane sulfonic acid and trifluoroacetic acid. The PPD solution showed maximum absorption and emission at 601 and 628 nm, respectively. Thin film transistors were fabricated by vacuum deposition and solution casting method. The electron mobilities of the devices were achieved as high as $0.17{\times}10^{-6}cm^2/Vs$ for vacuum deposited device and $0.4{\times}10^{-6}cm^2/Vs$ for spin coated device, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.189.2-189.2
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• 2013

1차원 산화아연 나노구조물은 광대역 에너지 밴드갭(~3.3 eV)과 독특한 물리적 특성을 갖고 있어, 전계효과 트랜지스터(field effect transistor), 발광다이오드(light emitting diode), 자외선 광검출기 (ultraviolet photodetector) 및 태양전지(photovoltaic cell)에 널리 이용되고 있다. 특히, 1차원 산화아연 나노구조물은 직접천이형 에너지 밴드갭(direct bandgap)을 갖고 있으며, 빛으로부터 여기된 전자가 1차원 나노구조물을 통해 향상된 이동경로를 제공할 수 있어서 차세대 자외선 광검출기 응용에 대한 연구가 활발히 진행되고 있다. 한편, 수열합성법(hydrothermal method)을 통해서 1차원 산화아연 나노구조물을 비교적 간단하고 저온공정을 통해서 합성할 수 있는데, 이를 광검출기 소자구조에 응용에서 양전극에 연결하기 위해서는 복잡하고 정교한 공정이 필요하다. 이에 본 연구에서는 수열합성법을 통해 합성된 산화아연 나노로드가 포함된 에탄올 용액을 금(Au) 패턴에 drop-casting을 통해서 간단한 방법으로 metal-semiconductor-metal (MSM) 광검출기를 제작하여 광반응 특성을 분석하였다. 또한 염료를 통해 가시광을 흡수하여 광전류(photocurrent)를 발생시킬 수 있도록 염료를 흡착한 산화아연 나노로드를 이용하여 같은 구조의 MSM 광검출기를 제작하여 가시광에 대한 광반응 특성을 관찰하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.204-204
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• 1999

The plasma source ion implantation(PSII) technique which is a method using high negative voltage pulse in plasma system has the potential to change the surface properties of polymer. PSII technique increase the surface free energy by introducing polar functional groups on the surface so that it improves reactivity, hydrophilicity, adhension, biocompatability, etc. However, the mobility of polymer chains enables the modified surface layers to adapt their composition to interfacial force. This hydrophobic recovery interrupts the stability of modified surfaces to keep for the long time. In this study, poly(methyl methacrylate)(PMMA), poly(2-hydroxyethyl methacrylate)(PHEMA), and polu(2-hydroxypropyl methacylate)(PHPMA) for contact lens application, were modified to improve the wettability with PSII technique and were investigated the surface stabilities. Polymer film was prepared with solution casting(3 wt.% solution) and was annealed at 11$0^{\circ}C$ under vacuum oven to remove solvent completely and to eliminate physical ageing. The thickness of the film measured by scanning electron microscopy (SEM) and surface profilometer was about 10${\mu}{\textrm}{m}$. Polymers were treated with different kinds of gases, pulse frequency, pulse with, pulse voltage, and treatment time. Even though PMMA, PHEMA, and PHPMA have similar repeat unit structure, the optimal treatment conditions and the tendency to hydrophobic recovery were different. PHPMA, more hydrophilic polymer than PMMA and PHEMA showd better wettability and stability after mild treatment. Surface tensions were obtained by water and diiodomethane contact angle measurements to monitor the relation between hydrophobic recovery and polymer structure. Different ion species in plasma change the polar component and dispersion component of polymer surface. For better wettability surface, the increase of polar component was a dominant factor. We also characterized modified polymer surfaces using x-ray photoelectron spectroscopy(XPS), secondary ion mass spectrometry(SIMS), Fourier Transform infrared spectroscopy(FT-IR), and SEM.

• Membrane Journal
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• v.22 no.1
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• pp.46-53
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• 2012

Low-temperature carbon dioxide stripping by a vacuum membrane stripping technology was studied as a substitute for the stripping process in a conventional aqueous amine process. Composite membranes with $5{\mu}m$ thickness of PDMS (polydimethylsiloxane) dense layer on a PE (polyethylene) support layer were prepared by a casting method and used as a membrane contactor for $CO_2$ stripping. Aqueous amine solutions of 30 wt% MEA (monoethanolamine) were used as absorbents. $CO_2$ flux was examined under various operating conditions by varying the vacuum pressure (60~360 mmHg (abs.)), stripping temperature ($25{\sim}80^{\circ}C$), $CO_2$ loading (0.5~0.7). $CO_2$ stripping flux increased with increasing temperature and $CO_2$ loading as well as decreasing vacuum pressure. PDMS-PE composite membrane has stability for vacuum stripping process compared with PTFE porous membrane.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.303-306
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• 2001

To shorten the delivery time for new products, a lot of prototype plastic parts manufacturing technologies have been developed including injection molding, vacuum casting, thermal forming and so on. Among them, RIM is becoming one of a important soft tooling methods to produce prototype and mass production parts within short time. Further more, as the rapid prototyping technology based tooling methods are playing an important role in prototype manufacturing industry, the utility of the RIM is increasing. But few analyses and mold design techniques have been developed so far due to its chemical and mechanical complexity during the packing and curing process. This research suggests mold gate design criteria to prevent bobbles from molded parts through simplified mathematical model and change of bubble sizes according to the geometry of the molded parts through experiments. Also this study shows the differences of bobble generation mechanism between RIM and injection molding.