• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.450-450
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• 2006

Organic light-emitting diodes (OLED) as pixels for flat panel displays are being actively pursued because of their relatively simple structure, high brightness, and self-emitting nature [1, 2]. The top-emitting diode structure is preferred because of their geometrical advantage allowing high pixel resolution [3]. To enhance the performance of TOLEDs, it is important to deposit transparent top cathode films, such as transparent conducting oxides (TCOs), which have high transparency as well as low resistance. In this work, we report on investigation of the characteristics of an indium tin oxide (ITO) cathode electrode, which was deposited on organic films by using a radio-frequency magnetron sputtering method, for use in top-emitting organic light emitting diodes (TOLED). The cathode electrode composed of a very thin layer of Mg-Ag and an overlaying ITO film. The Mg-Ag reduces the contact resistivity and plasma damage to the underlying organic layer during the ITO sputtering process. Transfer length method (TLM) patterns were defined by the standard shadow mask for measuring specific contact resistances. The spacing between the TLM pads varied from 30 to $75\;{\mu}m$. The electrical properties of ITO as a function of the deposition and annealing conditions were investigated. The surface roughness as a function of the plasma conditions was determined by Atomic Force Microscopes (AFM).

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.212-212
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• 2000

Since the first obserbvation of carbon nanotubes, extensive researches have been done for the synthesis using arc discharge, laser vaporization, and plasma-enhanced chemical vapor deposition. Carbon nanotubes have unique physical and chemical properties and can allow nanoscale devices. Vertically aligned carbon nanotubes with high quality on a large area is particularly important to enable both fundamental studies and applications, such as flat panel displays and vacuum microelectronics. we have grown vertically aligned carbon nanotubes on a large area of Si substrates by thermal chemical vapor deposition using C2H2 gas at 750-950$^{\circ}C$. we deposited catalytic metal on Si susbstrate using thermal evaporation. The nanotubes reveal highly purified surface. The carbon nanotubes have multi-wall structure with a hollow inside and it reveals bamboo structure agreed with base growth model. Figure 1 shows SEM micrograph showing vertically aligned carbon nanotubes whih were grown at 950$^{\circ}C$ on a large area (20mm${\times}$30mm) of Si substrates. Figure 2 shows TEM analysis was performed on the carbon nanotubes grown at 950$^{\circ}C$ for 10 min. The carbon nanotubes are multi-wall structure with bamboo shape and the lack of fringes inside the nanotube indicates that the core of the structure is hollow. In our experiment, carbon nanotubes grown by the thermal CVD indicate base growth model.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.263-263
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• 2010

투명도전막(indium tin oxide; ITO)은 투명하면서도 전기 전도도가 높기 때문에, 액정표시소자(LCD; Liquid Crystal Display), 전자발광소자(ELD; Electroluminescent Display) 및 전자 크로믹 소자(Electrochromic Display)를 포함하는 평판형 표시 소자(FPD; Flat Panel Display)와 태양전지 등에 이용되고 있다. 낮은 비저항과 높은 투과율의 ITO 박막은 $300^{\circ}C$ 이상의 고온에서 코팅해야 하는 것으로 알려져 있다. 그러나 최근 플라스틱과 같은 연성 소자가 전자부품에 널리 이용되면서 ITO를 저온에서 증착해야할 필요성이 대두되고 있다. 본 연구에서는 ITO를 플라스틱에 적용하기 위한 저온 코팅 공정 및 시편의 전 후처리공정을 개발하여 박막의 특성을 알아보고자 한다. 실험에 사용된 기판은 고투과율의 고분자(polyethylene terephthalate; PET) 필름이며 $5\;{\times}\;10\;cm^2$의 크기로 절단하여 알코올로 초음파 세척을 실시하였고, 진공 용기에 장입한 후 펄스전원을 이용하여 3분간 in-situ 청정을 실시하였다. ITO 코팅은 마그네트론 스퍼터링을 이용하였으며, 코팅시간, 전처리, 후처리, 기판온도, 산소유량 등 코팅 조건에 따른 박막의 특성을 조사하였다. ITO 박막의 코팅 조건에 따른 박막의 결정구조 분석은 x-선 회절(x-ray diffraction; XRD)을 이용하였고, 박막의 표면형상과 두께 보정 및 단면의 미세조직과 결정 성장 여부 등은 투과전자 현미경(transmission electron microscope; TEM)을 이용하여 분석하였다. 또한 ITO 박막의 면저항과 분광특성은 four-point Probe (CMP-100MP, Advanced Instrument Technology), spectrophotometer (UV-1601, SHIMADZU)를 이용하여 측정하였다. ITO 박막의 광학특성 분석 결과 전광선 투과율은 두께에 따라 변화 하였지만, 색차와 Haze 값은 증착 조건에 따라 큰 차이는 보이지 않았다. 그리고 박막의 결정화에 영향을 주는 가장 중요한 인자는 기판온도이지만, 기판온도를 높이지 못할 경우 비평형 마그네트론(unbalanced-magnetron; UBM)에 의해서 플라즈마 밀도를 높이는 방법으로 유사한 효과를 얻을 수 있음을 확인하였다.

• Korean Journal of Materials Research
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• v.21 no.7
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• pp.371-376
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• 2011

We report on the effects of $TiO_2$ doping power on the characteristics of multicomponent $TiO_2$-ITO (TITO) electrodes prepared by a multi-target sputtering system with tilted cathode guns. Both as-deposited and annealed TITO electrodes showed linearly increased sheet resistance and resistivity with increasing $TiO_2$ doping power. However, the TITO electrodes exhibited a fairly high optical transmittance regardless of the $TiO_2$ doping power due to the high transparency of the $TiO_2$. Although the annealed TITO showed much lower sheet resistance and resistivity relative to the as-deposited samples, the electrical properties of the annealed samples exhibited similar dependence on the $TiO_2$ power to the as-deposited samples. In addition, it was found that doping of an anatase $TiO_2$ in the ITO electrode prevented the preferred (222) orientation of the TITO electrodes. Although the TITO electrode showed higher sheet resistance and resistivity than that of the pure ITO electrode, it offers a very smooth surface and usage of a low-cost Ti element. It is thus considered a promising multicomponent transparent conducting electrode for cost-efficient flat panel displays and photovoltatics.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.233-236
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• 2014

Organic light emitting diodes (OLEDs) received much attention from both academia and industry as the next-generation flat panel displays. However, to produce high quality OLEDs, there are still many challenges to overcome. Especially, in full color OLEDs, the intrinsic wide band gap of the blue emitting materials results in inferior efficiency compared to those of green and red emitting materials. Therefore, extensive research efforts have been devoted to develop efficient blue emitting materials. This review briefly summarizes the basics of OLEDs and introduces highlights of research efforts in blue-emitting materials.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.2
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• pp.79-85
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• 2006

As the portable information appliance is developed, the demand of flat panel display equipments and parts are steeply increased. Most of all, the applications of LCD such as LCD TV, monitor, digital camera, CNS(car navigation system) and game machine become diversified. With the result that the number of BLU production enterprise is increased and the research on the design of backlight with the superior optical properties is persistently in progress. In this study we developed the pattern design tools for CCFL(cold cathode flourescent lamp) backlight to improve the conventional pattern design environment in which the pattern is designed manually from the experience and the trial and error. For the verification of our research, we designed the light reflection surface patterns for a real model of backlight and we measured the brightness uniformity using the BM-7. From the brightness uniformity measurement, the BLU designed using the presented tool showed the tolerable performance only in the first try of pattern design rather than the fifth try of pattern design in case of the conventional pattern design.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.4
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• pp.754-759
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• 2007

Field emission displays (FED) are currently being explored as a potential flat panel display technology. Specifically, the optimization pf efficient bin emitting phosphors in the $Y_2O_3-Nb_2O_5$ system and influence of particle size of phosphors on the luminescent properties was studied. Under 254 nm excitation, Bi activated $YNbO_4$ phosphors showed a strong and relatively narrow blue omission band, peaking at about 420-450 nm. Especially 0.4 wt% Bi doped yttrium phosphors showed the maximum emission intensity which is almost three times as much as that of $Y_2SiO_5:Ce$ phosphors. Finally, Ce doped $Y_2SiO_5$ phosphors exhibited strong and broad blue emission band, centered at 390-420 nm and maximum emission intensity at the doping concentration of 0.02-0.03 mol.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.182-189
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• 2021

VPS(Void Plywood Slab System, VPS) has optimized the shape of the hollow material. In addition, it has a function to prevent the floating of the hollow material and the separation due to the working load. In this study, the punching shear capacity of flat plate was performed using Void Plywood Slab System with form work panel proposed in the previous study. As a result of the test, the strength of the VSPS specimen in which the hollow material was placed beyond 2.0 times the column width from the loading point was reduced by 9.4% compared to the reference specimen. However, the strength value was about 1.57 times higher than the design value suggested by KBC 2016. It was found that there was no change in stiffness compared to the reference specimen until shear failure occurred in the VSPS specimen in which the hollow material was placed. It can be seen that this experiment is being destroyed by shear as the flexural reinforcing bars are sufficiently reinforced.

• Journal of Korean Neurosurgical Society
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• v.62 no.5
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• pp.526-535
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• 2019

Objective : While the risk of aneurysmal rebleeding induced by catheter cerebral angiography is a serious concern and can delay angiography for a few hours after a subarachnoid hemorrhage (SAH), current angiographic technology and techniques have been much improved. Therefore, this study investigated the risk of aneurysmal rebleeding when using a recent angiographic technique immediately after SAH. Methods : Patients with acute SAH underwent immediate catheter angiography on admission. A four-vessel examination was conducted using a biplane digital subtraction angiography (DSA) system that applied a low injection rate and small volume of a diluted contrast, along with appropriate control of hypertension. Intra-angiographic aneurysmal rebleeding was diagnosed in cases of extravasation of the contrast medium during angiography or increased intracranial bleeding evident in flat-panel detector computed tomography scans. Results : In-hospital recurrent hemorrhages before definitive treatment to obliterate the ruptured aneurysm occurred in 11 of 266 patients (4.1%). Following a univariate analysis, a multivariate analysis using a logistic regression analysis revealed that modified Fisher grade 4 was a statistically significant risk factor for an in-hospital recurrent hemorrhage (p=0.032). Cerebral angiography after SAH was performed on 88 patients ${\leq}3$ hours, 74 patients between 3-6 hours, and 104 patients >6 hours. None of the time intervals showed any cases of intra-angiographic rebleeding. Moreover, even though the DSA ${\leq}3$ hours group included more patients with a poor clinical grade and modified Fisher grade 4, no case of aneurysmal rebleeding occurred during erebral angiography. Conclusion : Despite the high risk of aneurysmal rebleeding within a few hours after SAH, emergency cerebral angiography after SAH can be acceptable without increasing the risk of intra-angiographic rebleeding when using current angiographic techniques and equipment.

• Journal of the Korean Society of Urban Environment
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• v.18 no.4
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• pp.503-509
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• 2018

In this study, a Proton-Transfer Reaction-Time-of-Flight Mass spectrometer (PTR-TOF-MS) was used for the continuous monitoring of Volatile Organic Compounds (VOCs) emitted from semiconductor workplace such as photolithography (PHOTO), flat panel display (FPD), organic light emitting diode (OLED), etching (WET) process. The averaged VOCs mixing ratio in the such workplace, PHOTO was 6.5 ppm, FPH was 6.4 ppm, WET was 2.0 ppm and OLED was 1.3 ppm, respectively. The abundance of VOCs in the workplace were methyl ethyl ketone (MEK) with 2.8 ppm (69%) and acetaldehyde with 0.5 ppm (13.2%). Depending on the semiconductor process characteristics, various VOCs have been observed in the workplace. The VOCs mixing ratio are lower than the workplace regulation standard (TWA), it is necessary to continuously monitor and effectively manage these VOCs.