• Journal of the Korean Magnetics Society
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• v.27 no.2
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• pp.41-48
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• 2017

Recent study shows that ordered alloy of $L1_2$ $XPt_3$ (M = V, Cr, Mn, Co, and Fe) exhibits various magnetic phases such as ferromagnetic-to-antiferromagnetic transition at the $MnPt_3$ surface. Moreover, it has been argued that $CrPt_3$, in particular, possess large magnetocrystalline anisotropy and Kerr rotation with possible violation of Hund's rule. As such, we extend our work to thickness dependence of the magnetic structure of $CrPt_3$ thin film using density functional theory. Magnetic ground state of the bulk $CrPt_3$ turns out to be ferromagnetic (FM), where other magnetic phases such as A-type (A-AF), C-type (C-AF), and G-type antiferromagnetic (G-AF) state have higher total energies than FM by 0.517, 0.591, and 0.183 eV, respectively, and magnetic moments of Cr in bulk are respectively 2.807 (FM), 2.805 (A-AF), 2.794 (C-AF) and $2.869_{{\mu}_B}$ (G-AF). We extend our study to $CrPt_3$(001) thin films with CrPt-and Pt-termination. The thickness and surface-termination dependences of magnetism are investigated for 3-9 monolayers (ML), where different magnetic phases from bulk emerge: C-AF for CrPt-terminated 3 ML and G-AF for Pt-terminated 5 ML have energy difference relative to FM by 8 and 54 meV, respectively. Furthermore, thickness- and surface-termination-dependent magnetocrystalline anisotropies of the $CrPt_3$(001) films are discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.425-433
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• 2000

The stochiometric mix of evaporating materials for the $CuGaTe_2$single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuGaTe_2$polycrystal, it was found tetragonal structure whose lattice constant $a_0 and c_0$ were 6.025 $\AA$ and 11.931 $\AA$, respectively. To obtain the single crystal thin films, $CuGaTe_2$mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $670^{\circ}C$ and $410^{\circ}C$ respectively, and the thickness of the single crystal thin films is 2.1$\mu\textrm{m}$. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of van der Pauw and studied on carrier density and mobility dependence on temperature. The carrier density and mobility of $CuGaTe_2$single crystal thin films deduced from Hall data are $8.72{\times}10{23}$개 $\textrm m^3$, $3.42{\times}10^{-2}$ $\textrm m^2$/V.s at 293K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuGaTe_2$single crystal thin film, we have found that the values of spin orbit coupling $\Delta$s.o and the crystal field splitting $\Delta$cr were 0.0791 eV and 0.2463 eV at 10 K, respectively. From the PL spectra at 10 K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0470 eV and the dissipation energy of the donor-bound exciton and acceptor-bound exciton to be 0.0490 eV, 0.0558 eV, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.1
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• pp.61-66
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• 2012

Chemical Mechanical Planarization (CMP) is a polishing process used in the microelectronic fabrication industries to achieve a globally planar wafer surface for the manufacturing of integrated circuits. Pad conditioning plays an important role in the CMP process to maintain a material removal rate (MRR) and its uniformity. For metal CMP process, highly acidic slurry containing strong oxidizer is being used. It would affect the conditioner surface which normally made of metal such as Nickel and its alloy. If conditioner surface is corroded, diamonds on the conditioner surface would be fallen out from the surface. Because of this phenomenon, not only life time of conditioners is decreased, but also more scratches are generated. To protect the conditioners from corrosion, thin organic film deposition on the metal surface is suggested without requiring current conditioner manufacturing process. To prepare the anti-corrosion film on metal conditioner surface, vapor SAM (self-assembled monolayer) and FC (Fluorocarbon) -CVD (SRN-504, Sorona, Korea) films were prepared on both nickel and nickel alloy surfaces. Vapor SAM method was used for SAM deposition using both Dodecanethiol (DT) and Perfluoroctyltrichloro silane (FOTS). FC films were prepared in different thickness of 10 nm, 50 nm and 100 nm on conditioner surfaces. Electrochemical analysis such as potentiodynamic polarization and impedance, and contact angle measurements were carried out to evaluate the coating characteristics. Impedance data was analyzed by an electrical equivalent circuit model. The observed contact angle is higher than 90o after thin film deposition, which confirms that the coatings deposited on the surfaces are densely packed. The results of potentiodynamic polarization and the impedance show that modified surfaces have better performance than bare metal surfaces which could be applied to increase the life time and reliability of conditioner during W CMP.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.12
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• pp.909-914
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• 2013

CIGS is one of thin film solar cell and has been studied so much, because of the possibility of low price and high efficiency. Until now, co-evaporation and sputtering were typical method to prepare CIGS absorption layer, and a few company commercialized solar cell by these method. However, non-vacuum process which has been studied for long time has not been progressed, though the merit of low price. Especially, aerosol deposition method has not been reported, because it is difficult to prepare a large quantity of various CIGS powder. In this study, CIGS powder was synthesized by mechanochemical method and CIGS absorption layer was deposited by aerosol deposition method. The thickness of the CIGS layer was controlled by the number of deposition and the surface roughness of it was affected by the amount of flow gas. And, also, I-V curve of it appeared metallic property in the case of 'as deposition'. After heat treatment in Se-rich atmosphere, the electrical property of it changed to a semiconductor. CdS and transparent conduction layer were formed by a typical method on it for solar cell. The efficiency of cell was appeared 0.19%. Though the efficiency was low because of the disharmony in the after-process, it was conformed that CIGS solar cell could be prepared by aerosol deposition.

• Journal of the Korean Home Economics Association
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• v.37 no.7
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• pp.29-43
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• 1999

The purpose of this study was to develop disposable diapers for the elderly in need by experimenting with wearing disposable diapers and analyzing the properties of materials of these diapers. The diapers were of two different types: one was a panty type for the elderly who were bed ridden, and the other was a pad type for the elderly who had incontinence. The subjects for the wearing test of the panty type were forty who were bed ridden, and there were forty subjects for the wearing test of the pad type who had incontinence. The disposable diapers for these experiments were chosen from those already found in the market place. Four panty types and three pad types were selected. From these experiments for the disposable diapers, the first prototypes were developed, and the second prototypes were proposed by experimenting with the first prototypes. The first panty prototype was designed to improve absorbing power, and we added waist rubber bands to prevent evacuation from back leaking and a frontal tape to prevent waistline film from tearing. The first pad prototype was designed to improve absorbing power also, and we added side rubber bands to prevent the side leaking and an adhesive tape on the fore part of the bottom to prevent the diapers from moving, and made the outline of the back area curved and thin to help hide the diaper from detection thus making the wearer feel better. From these test cases and analyzing the properties of materials with the first prototypes, we gained some success, but several points on further improvements were proposed to refine the final prototypes. The second panty prototype we proposed was to make 1he length longer, especially in the crotch area to prevent excess leaking and to fit the body more snugly. Also, the second pad prototype was proposed to reduce the total thickness of the diaper, and to improve the feeling and appearance.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3355-3360
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• 2012

To promote the photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs), graphene is introduced as a working electrode with $TiO_2$ in this study, because it has great transparency and very good conductivity. XRD patterns indicate the presence of graphene and $TiO_2$ particles in graphene-linked $TiO_2$ samples. Moreover, TEM pictures also show that the nano-sized $TiO_2$ particles are highly dispersed and well-linked onto the thin layered graphene. On the basis of the UV-visible spectra, the band gaps of $TiO_2$, 1.0 wt % graphene-$TiO_2$, 5.0 wt % graphene-$TiO_2$, and 10.0 wt % graphene-$TiO_2$ are 3.16, 2.94, 2.25, and 2.11 eV, respectively. Compared to pure $TiO_2$, the energy conversion efficiency was enhanced considerably by the application of graphene-linked $TiO_2$ anode films in the DSSCs to approximately 6.05% for 0.1 wt % graphene-$TiO_2$ with N719 dye (10.0 mm film thickness and $5.0mm{\times}5.0mm$ cell area) under $100mW/cm^2$ of simulated sunlight. The quantum efficiency was the highest when 1.0 wt % of graphene was used. In impedance curves, the resistance was smallest for 1.0 wt % graphene-$TiO_2$-DSSC.

• Journal of the Semiconductor & Display Technology
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• v.14 no.1
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• pp.61-65
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• 2015

We have fabricated poly(3,4-ethylenedioxythiophene) : poly(4-styrenesulfonate) (PEDOT : PSS) thin films using a slotdie coater for the applications of OLED lightings. It is demonstrated that the properties of slot-die coated PEDOT : PSS films are comparable with those of spin-coated ones. Namely, the average and peak-to-peak roughness of the slot-die coated 50-nm-thick PEDOT : PSS film are measured to be as low as 0.247 nm and 1.3 nm, respectively. Moreover, we have obtained excellent thickness uniformity (~1.91%). With the slot-die coated PEDOT : PSS films, we have fabricated green phosphorescent OLED devices. For comparison, we have also fabricated OLED devices with spin-coated PEDOT : PSS films. Both show almost no discrepancy in device performance. The power efficiency (25.4 lm/W) and emission uniformity (77%) of OLEDs with slot-die coated PEDOT : PSS films are shown to be slightly lower than those (27.3 lm/W, 80%) of OLEDs with spin-coated PEDOT : PSS films at the luminance of 1,000nit, increasing the feasibility of using a slot-die coating process for the fabrication of large-area OLED lighting sources at a competitive price.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.2
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• pp.6-12
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• 1998

Thin film SOI(Silicon-on-insulator) device offer unique advantages such as reduction in short channel effects, improvement of subthreshold slope, higher mobility, latch-up free nature, and so on. But these devices exhibit floating-body effet such as current kink which inhibits the proper device operation. In this paper, the SOI NMOSFET with a T-type gate structure is proposed to solve the above problem. To simulate the proposed device with TSUPREM-4, the part of gate oxide was considered to be 30nm thicker than the normal gate oxide. The I-V characteristics were simulated with 2D MEDICI. Since part of gate oxide has different oxide thickness, the gate electric field strength is not same throughout the gate and hence the impact ionization current is reduced. The current kink effect will be reduced as the impact ionization current drop. The reduction of current kink effect for the proposed device structure were shown using MEDICI by the simulation of impact ionization current, I-V characteristics, and hole current distribution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.6
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• pp.409-414
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• 2017

The aim of this study is to understand the phonon transfer characteristics of a silicon thin film transistor. For this purpose, the Joule heating mechanism was considered through the electron-phonon interaction model whose validation has been done. The phonon transport characteristics were investigated in terms of phonon mean free path for the variations in the device power and silicon layer thickness from 41 nm to 177 nm. The results may be used for developing the thermal design strategy for achieving reliability and efficiency of the silicon-on-insulator (SOI) transistor, further, they will increase the understanding of heat conduction in SOI systems, which are very important in the semiconductor industry and the nano-fabrication technology.

• Journal of Conservation Science
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• v.22
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• pp.61-76
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• 2008

We examined characterizations of Paraloid B72 films when it dissolved in four different solvents-acetone, MEK, toluene and xylene. The surface before and after coating were observed by optical microscope and AFM. Thickness and contact angle of films was measured and surface energy was calculated for grasping properties of films. We also tested adhesive strength of films by scratch tester and durability of films by performing yellowing test. The result was that xylene has better coating property than other solvents. Because 10% Paraloid B72 in xylene film is even, non-mottled, thin, stabilized in yellowish and has proper hydrophobic, we confirmed xylene is good solvent for bronze artifact conservation. However, other tests will need for finding appropriate concentration of Paraloid B72.