• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.126-126
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• 2018

최근 차세대 디스플레이인 flexible 하고 transparent 한 디스플레이 개발이 진행 중 이며, 이러한 디스플레이가 개발 되기 위해 백 플레인으로 사용되는 Thin Film Transistor (TFT) 또한 차세대 디스플레이 못지 않게 연구가 진행 되고 있다. 기존의 무기물을 기반으로 하고 Rigid한 TFT는 현재 많은 곳에 적용이 되어 사람들이 사용 하고 있다. 하지만 이미 시장은 포화상태이며 차세대 디스플레이 컨셉인 flexible 하고 투명한 것과 맞지 않는다. 그래서 유연하며 투명한 특성을 가진 TFT에 대한 연구가 활발히 진행 되고 있으며 많은 성과를 이루었다. 이러한 소자를 이용하여 훗날 Electronic-skin(e-skin)이라 부르는 전자 피부를 활용하여 실시간 모니터링 할 수 있는 헬스 케어 분야 등에 활용 가치 또한 높다. 현재 유연하며 투명한 기판 및 물질 개발에 많은 연구 개발이 진행 되고 있다. 하지만 유연한 기판을 사용하여 TFT를 제작한 후 stress나 bending에 대한 내구성과 안정성, 신뢰성 등이 무기물을 기반으로 한 TFT에 비해 좋지 않은 실정이다. 따라서 유연하며 투명한 기판을 사용한 TFT에 대한 안정성, 신뢰성 등을 확보하여야 한다. 본 연구 에서는 유연한 기판을 사용하여 TFT를 제작 한 후, TFT특성과 안정성을 확보하는 것을 목표로 실험을 진행하였다. 우리는 Mo전극과 Parylene 기판을 사용하여 유연한 TFT소자를 탑 게이트 구조로 제작 하였고 Rigid한 Glass기판 위에 Floating Process를 진행하기 위해 PVA층을 코팅 후 그 위에 Parylene을 CVD로 증착 하고 IGZO를 Sputter를 사용해 증착했다. Parylene은 DI Water 70도에서 Floating 공정을 통해 Rigid 기판에서 탈착 시켰다. 유연한 기판 위에 TFT를 제작 후 bending에 대한 특성 변화 및 안정성에 대한 측정을 실시하였다. Bending에 대한 특성 변화는 우수한 결과가 나왔지만 안정성 측정 중 Negative Bias Stress(NBS) 상에서 비정상적인 On Current Drop 현상이 발생 되었다. Parylene과 Channel층 사이 interface roughness로 인해 charge trap이 되고 이로 인해 On Current Drop 이라는 현상으로 나타났다. 그래서 우리는 Parylene 기판과 Channel 층간의 surface roughness를 개선하기 위한 방법으로 UV Treatment를 사용하였고 시간을 다르게 하여 surface 개선을 진행했다. Treatment 시간을 증가 시킴에 따라 Surface roughness가 많이 좋아 졌으며, Surface를 개선하고자 비정상적인 On Current Drop 현상이 없어졌으며 위 실험으로 Polymer의 surface roughness에 따라 TFT에 대한 안정성에 대한 신뢰성이 확보 될 수 있는 것을 확인 하였다.

• The Journal of Natural Sciences
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• v.4
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• pp.179-189
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• 1991

The limit sowing time and the growth of radish cultivated in late fall were studied in relation to the effects of varieties and polyethylene film mulching. The root weight of Dehyung-Chusuk radish sowing in September 8th in Suwon was 520g but 718g in mulched plot. In Pusan the root weight of radish sowing on September 16th and harvested on November 23rd was 655g in Bekkyung and 813g in Dehyung-Chusuk variety, but more than 1000g in mulched plots of two varieties all. The effect of mulching was higher in Dehyung-Chusuk than in Bekkyung. The experimental results of Altari varieties will be recommandable in limit sowing time as around September 14th in mid-northern area and around September 18th in mid-southern area. Chonggak Altari was better than Chammat Altari in root formatiion. Two varieties all revealed good growth in the plots of sowing on September 26th in Pusan.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.492-497
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• 2001

We report the characteristics and the dependence of sputter-deposited Ta films on the process parameters. The properties of as-deposited Ta films such as deposition rate, resistivity, Rs uniformity, reflectivity, and stress were investigated and analyzed as a function of process parameter using a statistical experimental method. The functional relationships between the independent and dependent variables were predicted by surface response. The optimal deposition condition of DC magnetron sputtered Ta films was obtained at the chamber pressure of 2 mTorr, power density of 8 W/$\textrm{cm}^2$, and substrate temperature of 2$0^{\circ}C$ by means of resistivity and Rs uniformity. The fitness value for quadratic model as evaluated by the R- square was 0.85~ 0.9 without pooling. The as-deposited Ta films exhibited the resistivity of ~180$\mu$$\Omega$cm with Rs uniformity of ~2%. The transmission electron microscopy and x-ray diffractometry identified that the phase of as-deposited film was $\beta$-Ta having the grain size of 100~200.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.845-852
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• 2011

The Spark Plasma Sintering(SPS) method offers a means of fabricating a sintered-body having high density without grain growth through short sintering time and a one-step process. A titanium compact having high density and purity was fabricated by the SPS process. It can be used to fabricate a Ti sputtering target with controlled parameters such as sintering temperature, heating rate, and pressure to establish the optimized processing conditions. The compact/target(?) has a diameter of ${\Phi}150{\times}6.35mm$. The density, purity, phase transformation, and microstructure of the Ti compact were analyzed by Archimedes, ICP, XRD and FE-SEM. A Ti thin-film fabricated on a $Si/SiO_2$ substrate by a sputtering device (SRN-100) was analyzed by XRD, TEM, and SIMS. Density and grain size were up to 99% and below $40{\mu}m$, respectively. The specific resistivity of the optimized Ti target was $8.63{\times}10^{-6}{\Omega}{\cdot}cm$.

• Journal of IKEEE
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• v.22 no.4
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• pp.1230-1233
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• 2018

$Al_2O_3$ films with the thickness of 50 nm were fabricated on 4H-SiC by aerosol deposition, and their electrical properties were characterized with different post annealing conditions. As a result, the $Al_2O_3$ film annealed in $N_2$ atmosphere showed decreased fixed charge density at the interface area between the $Al_2O_3$ and SiC, and increased leakage currents due to the generation of oxygen vacancies. From this result, it was confirmed that proper $N_2$ and $O_2$ ratio for the post annealing process is important.

• Korean Journal of Optics and Photonics
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• v.30 no.4
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• pp.159-166
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• 2019

The trajectory of the transmission ellipsometric pseudoconstant ${\rho}=tan{\psi}_{\mu}e^{i{\Delta}_{\mu}}$ of a uniaxially anisotropic substrate like PET forms a circle in polar coordinates, as the phase-retardation angle is varied at a fixed azimuthal angle. The radius as well as the center's position of this circle are functions of the azimuthal angle only. This circle passes through the point (1,0), and the center of this circle is located on the real axis. These characteristics of the circle are examined analytically, and are utilized to derive simple expressions for the azimuthal angle and the phase-retardation angle of the uniaxially anisotropic substrate using the measured transmission ellipsometric constant. Finally, we confirm that the derived expressions are well applied to the analysis of the optical anisotropy of a PET film.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.451-465
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• 2021

In this investigation, electrochemical characteristics and damage behavior of 316L stainless steel polymer electrolyte membrane fuel cell(PEMFC) were analyzed by potentiodynamic and potentiostatic tests in cathode operating condition of PEMFC. As the result of potentiodynamic polarization test, range of passive region was larger than range of active region. In the result of potentiostatic test, damage depth and width, pit volume, and surface roughness were increased 1.57, 1.27, 2.48, and 1.34 times, respectively, at 1.2 V compared to 0.6 V at 24 hours. Also, as a result of linear regression analysis of damage depth and width graph, trend lines of damage depth and width according to applied potentials were 16.6 and 14.3 times larger, respectively. This demonstrated that applied potential had a greater effect on pitting damage depth of 316L stainless steel. The damage tendency values were 0.329 at 6 hours and 0.633 at 24 hours with applied potentials, representing rapid growth in depth direction according to the test times and applied potentials. Scanning electron microscopy images revealed that surface of specimen exhibited clear pitting damage with test times and applied potentials, which was thought to be because a stable oxide film was formed by Cr and Mo.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.138-143
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• 2022

We analyzed the influence of post-annealing on Ga₂O₃/n-type 4H-SiC heterojunction diode. Gallium oxide (Ga₂O₃) thin films were deposited by radio frequency (RF) sputtering. Post-deposition annealing at 950℃ in an Oxygen atmosphere was performed. The material properties of Ga₂O₃ and the electrical properties of the diodes were investigated. Atomic Force Microscopy (AFM), X-Ray Diffraction and Scanning Electron Microscope (SEM) images show a significant increase in the roughness and crystallinity of the O₂-annealed films. After Oxygen annealing X-ray Photoelectron Spectroscopy (XPS) shows that the atomic ratio of oxygen increases which is related to a decrease in oxygen vacancy within the Ga₂O₃ film. The O₂-annealed diodes exhibited higher on-current and lower leakage current. Moreover, the ideality factor, barrier height, and thermal activation energy were derived from the current-voltage curve by increasing the temperature from 298 - 434K.

• Journal of the Korea Convergence Society
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• v.13 no.3
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• pp.197-202
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• 2022

The CZTS solar cell is a thin film solar cell using an absorption layer composed of Cu, Zn, Sn, Se, and S, and is cheaper than a CIGS solar cell using In and Ga and more eco-friendly than a perovskite and CdTe solar cell using Pb and Cd. In this study, we conducted a bending test for flexible CZTS solar cells. Experiments were conducted in the direction of inner benidng with compressive stress and outer bending with tensile stress, and during the number of bending 1,000 times with a radius of curvature of 50 mmR, the efficiency of the solar cell decreased by up to 12.7%, and the biggest cause of efficiency reduction in both directions was a large decrease in parallel resistance.

• Journal of Hydrogen and New Energy
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• v.33 no.6
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• pp.808-818
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• 2022

In this research paper, we investigated the cryogenic line chill down characteristics of liquefied natural gas (LNG). A numerical analysis model was established and verified so that it can calculate the precise cooling characteristics of cryogenic fluid for the stable and safe utilization especially such as LNG and liquid hydrogen. The numerical modeling was programmed by C++ as an one-dimensional homogeneous model. The thermohydraulic cooling process was simulated using mass, momentum, energy conservation equations and appropriate heat transfer correlations. In this process, the relevant heat transfer correlations for nuclear boiling, transition boiling, film boiling, and single-phase heat transfer that can predict the experimental results were implemented. To verify the numerical modeling, several cryogenic line chill down experiments using LNG were conducted at the Korea Institute of Machinery & Materials (KIMM) LNG and Cryogenic Technology Center.