• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1030-1033
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• 2004

We herewith report for the effect of dielectric surface modification on the electrical characteristics of organic thin-film transistors (OTFTs). The kist-jm-1 as an organic molecule for the surface modification is deposited onto the surface of zirconium oxide ($ZrO_2$) gate dielectric layer. The OTFTs are elaborated on the flexible plastic substrates through 4-level mask process to yield a simple fabrication process. In this work, we also have examined the dependence of electrical performance on the interface surface state of gate dielectric/pentacene, which may be modified by chemical properties in the gate dielectric surface.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1116-1118
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• 2005

We studied laser crystallization of amorphous silicon films prepared at ultra low temperatures ($<150^{\circ}C$). Amorphous silicon films having a low content of hydrogen were deposited by using catalytic chemical vapor deposition method. Influence of process parameters on the hydrogen content was investigated. Laser crystallization was performed dispensing with the preliminary dehydrogenation process. Crystallization took place at a laser energy density value as low as $70\;mJ/cm^2$, and the grain size increased with increasing the laser energy. The ELA crystallization of Catalytic CVD a-Si film is a promising candidate for Poly-Si TFT in active-matrix flexible display on plastic substrates.

• Journal of the Korean Graphic Arts Communication Society
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• v.30 no.3
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• pp.45-56
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• 2012

Printing technology is accepted by appropriate technology that smart phones, tablet PC, display(LCD, OLED, etc.) precision recently in the electronics industry, the market grows, this process in the ongoing efforts to improve competitiveness through the development of innovative technologies. So printed electronics appeared by new concept. This technology development is applied on electronic components and circuits for the simplification of the production process and reduce processing costs. Low-temperature process making possible for widening, slimmer, lighter, and more flexible, plastic substrates, such as(flexible) easily by forming a thin film on a substrate has been studied. In the past, the formation of the electrode used a screen printing method. But the screen printing method is formation of fine patterns, high-speed printing, mass production is difficult. The roll-to-roll printing method as an alternative to screen printing to produce electronic devices by printing techniques that were used traditionally in the latest technology and processing techniques applied to precision control are very economical to implement fine-line printing equipment has been evaluated as. In order to function as electronic devices, especially the dozens of existing micro-level of non-dot print fine line printing is required, the line should not break at all, because according to the specifications required to fit the ink transfer conditions should be established. In this study of roll-to-roll printing conductive paste suitable for gravure offset printing by developing Ag paste for forming fine patterns to study the basic physical properties with the aim of this study were to.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.451-455
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• 2012

To compare an electrical and optical characteristics of indium tin oxide (ITO) and carbon nanotube (CNT) electrode on flexible and reflective display, we fabricate two charged particle-type display panels under the same panel condition of which the width of ribs is 10 ${\mu}m$, the cell size is $300{\mu}m{\times}300{\mu}m$, the q/m value of the white particles is -4.3 ${\mu}C/g$ and that for the black is +1.3 ${\mu}C/g$, and the cell gap is 75 ${\mu}m$, 125 ${\mu}m$, and 175 ${\mu}m$. We use plastic substrates coated with ITO and CNT electrode. To evaluate optical property, we measure a response time of particles using a laser and a photodiode. Threshold and driving voltages of CNT electrode according to the sheet resistance of 300, 600, 1,000 (ohm/sq) are compared with ITO electrode of 10 (ohm/sq). A response time of the CNT panel is similar to that of ITO panel, but the threshold and driving voltages of CNT panel are higher than that of ITO panel, inducing a large bombardment of the particles and shortening the lifetime of the panel. High difference of a threshold and a driving voltage of CNT panel will induce an particle clumping, resulting degradation of the panel. A bending radius of the fabricated CNT panel is 18 ${\mu}m$.

• Journal of Electrochemical Science and Technology
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• v.13 no.4
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• pp.453-461
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• 2022

A chemically sintered and binder-free paste of TiO₂ nanoparticles (NPs) was prepared using a binary-liquid mixture of 1-octanol and CCl₄. The 1:1 (v/v) complex of CCl₄ and 1-octanol easily interacted chemically with the TiO₂ NPs and induced the formation of a highly viscous paste. The as-prepared binary-liquid paste (P_BL)-based TiO₂ film exhibited the complete removal of the binary-liquid and residuals with the subsequent low-temperature sintering (~150℃) and UV-O₃ treatment. This facilitated the fabrication of TiO₂ photoanodes for flexible dye-sensitized solar cells (f-DSSCs). For comparison purposes, pure 1-octanol-based TiO₂ paste (P_O) with moderate viscosity was prepared. The P_BL-based TiO₂ film exhibited strong adhesion and high mechanical stability with the conducting oxide coated glass and plastic substrates compared to the P_O-based film. The corresponding low-temperature sintered P_BL-based f-DSSC showed a power conversion efficiency (PCE) of 3.5%, while it was 2.0% for P_O-based f-DSSC. The P_BL-based low- and high-temperature (500℃) sintered glass-based rigid DSSCs exhibited the PCE of 6.0 and 6.3%, respectively, while this value was 7.1% for a 500℃ sintered rigid DSSC based on a commercial (or conventional) paste.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.288-289
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• 2011

Indium Tin Oxide (ITO) is a typical highly Transparent Conductive Oxide (TCO) currently used as a transparent electrode material. Most widely used deposition method is the sputtering process for ITO film deposition because it has a high deposition rate, allows accurate control of the film thickness and easy deposition process and high electrical/optical properties. However, to apply high quality ITO thin film in a flexible microelectronic device using a plastic substrate, conventional DC magnetron sputtering (DMS) processed ITO thin film is not suitable because it needs a high temperature thermal annealing process to obtain high optical transmittance and low resistivity, while the generally plastic substrates has low glass transition temperatures. In the room temperature sputtering process, the electrical property degradation of ITO thin film is caused by negative oxygen ions effect. This high energy negative oxygen ions(about over 100eV) can be critical physical bombardment damages against the formation of the ITO thin film, and this damage does not recover in the room temperature process that does not offer thermal annealing. Hence new ITO deposition process that can provide the high electrical/optical properties of the ITO film at room temperature is needed. To solve these limitations we develop the Magnetic Field Shielded Sputtering (MFSS) system. The MFSS is based on DMS and it has the plasma limiter, which compose the permanent magnet array (Fig.1). During the ITO thin film deposition in the MFSS process, the electrons in the plasma are trapped by the magnetic field at the plasma limiters. The plasma limiter, which has a negative potential in the MFSS process, prevents to the damage by negative oxygen ions bombardment, and increases the heat(-) up effect by the Ar ions in the bulk plasma. Fig. 2. shows the electrical properties of the MFSS ITO thin film and DMS ITO thin film at room temperature. With the increase of the sputtering pressure, the resistivity of DMS ITO increases. On the other hand, the resistivity of the MFSS ITO slightly increases and becomes lower than that of the DMS ITO at all sputtering pressures. The lowest resistivity of the DMS ITO is $1.0{\times}10-3{\Omega}{\cdot}cm$ and that of the MFSS ITO is $4.5{\times}10-4{\Omega}{\cdot}cm$. This resistivity difference is caused by the carrier mobility. The carrier mobility of the MFSS ITO is 40 $cm^2/V{\cdot}s$, which is significantly higher than that of the DMS ITO (10 $cm^2/V{\cdot}s$). The low resistivity and high carrier mobility of the MFSS ITO are due to the magnetic field shielded effect. In addition, although not shown in this paper, the roughness of the MFSS ITO thin film is lower than that of the DMS ITO thin film, and TEM, XRD and XPS analysis of the MFSS ITO show the nano-crystalline structure. As a result, the MFSS process can effectively prevent to the high energy negative oxygen ions bombardment and supply activation energies by accelerating Ar ions in the plasma; therefore, high quality ITO can be deposited at room temperature.

• Polymer(Korea)
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• v.30 no.2
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• pp.140-145
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• 2006

The mort commonly available substrate material is glass in the display fibrication process. However, glass is not desirable due to its heaviness and fragility. Recently, plastics such polysulfone (PSF), polyethesulfone (PES), polycarbonate (PC), polyethylene terephthalate (PET) and cyclic olefin polymers (COP) have been investigated to replace glass as a substrate material for display fibrication. Plastic substrates are advantageous in that they are lightweight, huh impart resistance, flexibility, and ability for roll to roll manufacturing process. But many plastics have poor chemical resistance in organic solvent. The chemica resistance is also lequired because they are exposed to solvents for various chemical treatments din the manufacturing process. So, we have an interest in the chemical modification of PSF to improve chemical resistance. We introduced crosslinkable imide moieties using chloromethylation method for the modification of PSF which could be overcome above shortcomings for display substrate based on plastic film. We prepared the cross-linked polysulfone films which were represented chemical resistance in HeOH, THF, DMSO and NMP. The thermal properties were measured by TGA, DSC and TMA. As the results, we have confirmed to enhance of the thermal property. They had low coefficient of thermal expansion (CTE) which decreased to 15% and had increased $T_g\;from\;180^{\circ}C\;to\;252^{\circ}C$. Cross-linked polysulfone films with imide side-chain had good optical properties and chemical resistance so that they could be used as flexible display substrate.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.100-101
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• 2012

The plasma damage free and room temperature processedthin film deposition technology is essential for realization of various next generation organic microelectronic devices such as flexible AMOLED display, flexible OLED lighting, and organic photovoltaic cells because characteristics of fragile organic materials in the plasma process and low glass transition temperatures (Tg) of polymer substrate. In case of directly deposition of metal oxide thin films (including transparent conductive oxide (TCO) and amorphous oxide semiconductor (AOS)) on the organic layers, plasma damages against to the organic materials is fatal. This damage is believed to be originated mainly from high energy energetic particles during the sputtering process such as negative oxygen ions, reflected neutrals by reflection of plasma background gas at the target surface, sputtered atoms, bulk plasma ions, and secondary electrons. To solve this problem, we developed the NBAS (Neutral Beam Assisted Sputtering) process as a plasma damage free and room temperature processed sputtering technology. As a result, electro-optical properties of NBAS processed ITO thin film showed resistivity of $4.0{\times}10^{-4}{\Omega}{\cdot}m$ and high transmittance (>90% at 550 nm) with nano- crystalline structure at room temperature process. Furthermore, in the experiment result of directly deposition of TCO top anode on the inverted structure OLED cell, it is verified that NBAS TCO deposition process does not damages to the underlying organic layers. In case of deposition of transparent conductive oxide (TCO) thin film on the plastic polymer substrate, the room temperature processed sputtering coating of high quality TCO thin film is required. During the sputtering process with higher density plasma, the energetic particles contribute self supplying of activation & crystallization energy without any additional heating and post-annealing and forminga high quality TCO thin film. However, negative oxygen ions which generated from sputteringtarget surface by electron attachment are accelerated to high energy by induced cathode self-bias. Thus the high energy negative oxygen ions can lead to critical physical bombardment damages to forming oxide thin film and this effect does not recover in room temperature process without post thermal annealing. To salve the inherent limitation of plasma sputtering, we have been developed the Magnetic Field Shielded Sputtering (MFSS) process as the high quality oxide thin film deposition process at room temperature. The MFSS process is effectively eliminate or suppress the negative oxygen ions bombardment damage by the plasma limiter which composed permanent magnet array. As a result, electro-optical properties of MFSS processed ITO thin film (resistivity $3.9{\times}10^{-4}{\Omega}{\cdot}cm$, transmittance 95% at 550 nm) have approachedthose of a high temperature DC magnetron sputtering (DMS) ITO thin film were. Also, AOS (a-IGZO) TFTs fabricated by MFSS process without higher temperature post annealing showed very comparable electrical performance with those by DMS process with $400^{\circ}C$ post annealing. They are important to note that the bombardment of a negative oxygen ion which is accelerated by dc self-bias during rf sputtering could degrade the electrical performance of ITO electrodes and a-IGZO TFTs. Finally, we found that reduction of damage from the high energy negative oxygen ions bombardment drives improvement of crystalline structure in the ITO thin film and suppression of the sub-gab states in a-IGZO semiconductor thin film. For realization of organic flexible electronic devices based on plastic substrates, gas barrier coatings are required to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency flexible AMOLEDs needs an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}gm^{-2}day^{-1}$. The key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required (under ${\sim}10^{-6}gm^{-2}day^{-1}$) is the suppression of nano-sized defect sites and gas diffusion pathways among the grain boundaries. For formation of high quality single inorganic gas barrier layer, we developed high density nano-structured Al2O3 single gas barrier layer usinga NBAS process. The NBAS process can continuously change crystalline structures from an amorphous phase to a nano- crystalline phase with various grain sizes in a single inorganic thin film. As a result, the water vapor transmission rates (WVTR) of the NBAS processed $Al_2O_3$ gas barrier film have improved order of magnitude compared with that of conventional $Al_2O_3$ layers made by the RF magnetron sputteringprocess under the same sputtering conditions; the WVTR of the NBAS processed $Al_2O_3$ gas barrier film was about $5{\times}10^{-6}g/m^2/day$ by just single layer.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.104.1-104.1
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• 2011

가볍고, 유연성(flexibility)을 갖는 박막(thin film)형 플랙서블 태양전지(flexible solar cell)는 상황에 따른 형태의 변형이 가능하여, 휴대가 간편하고, 기존 혹은 신규 구조물의 지붕(rooftop)등에 설치가 용이하여, 차세대 성장 동력 분야에서 각광받고 있다. 그러나 아직까지 플랙서블 태양전지는 제작시 열에 의한 기판의 변형, 기판 이송시 너울 현상, 대면적 패터닝(patterning) 기술 등 많은 어려움 등으로 웨이퍼나 글라스 기판에 제조된 태양전지 대비 낮은 광전환 효율을 갖는다. 따라서 본 연구에서는 플랙서플 태양전지 성능개선을 위해 3.5세대급 ($450{\times}450cm^2$) 스퍼터(sputter), 금속유기 화학기상장치 (MOCVD), 플라즈마 화학기상장치 (PECVD), 레이저 가공장치 (Laser scriber)를 이용하여 a-Si:H/a-SiGe:H 이중접합(tandem)을 갖는 태양전지를 제작하였고, 광 변환효율 특성을 평가하였다. 전도도(conductivity), 라만(Raman)분광 및 UV/Visible 분광 분석을 통하여 박막의 전기적, 구조적, 광학적 물성을 평가하여 단위박막의 물성을 최적화 했다. 또한 제작된 태양전지는 쏠라 시뮬레이터 (Solar Simulator)를 이용하여 성능 평가를 수행하였고, 상/하부층의 전류 정합 (current matching)을 위해 외부양자효율 (external quantum efficiency) 분석을 수행하였다. 제작된 이중접합 접이식 태양전지로 소면적($0.25cm^2$)에서 8.7%, 대면적($360cm^2$ 이상) 8.0% 이상의 효율을 확보하였으며, 성능 개선을 위해 대면적 패턴 기술 향상 및 공정 기술 개선을 수행 중이다.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.887-892
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• 2019

In this study, after 20nm-thick $SiO_2$ thin film was deposited by PECVD method on the PES substrate, which is known to have the highest heat resistance among plastic substrates, as a buffer layer, ITZO thin films were deposited by RF magnetron sputtering method to investigate the electrical and optical properties according to the working pressure. The ITZO thin film deposited at the working pressure of 3mTorr showed the best electrical properties with a resistivity of $8.02{\times}10^{-4}{\Omega}-cm$ and a sheet resistance of $50.13{\Omega}/sq.$. The average transmittance in the visible region (400-800nm) of all ITZO films was over 80% regardless of working pressure. The Figure of merit showed the largest value of $23.90{\times}10^{-4}{\Omega}^{-1}$ in the ITZO thin film deposited at 3mTorr. This study found that ITZO thin films are very promising materials to replace ITO thin films in next-generation flexible display devices.