• 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.

• Journal of the Mineralogical Society of Korea
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• v.24 no.3
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• pp.235-244
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• 2011

A batch experiment of pyrite oxidation was performed and the surfaces of the reacted pyrite were regularly observed with the scanning electron microscope (SEM) together with the chemical compositions of the solution to help understand the oxidation mechanisms of pyrite by Acidithiobacillus ferrooxidans (Af). The dissolved Fe concentrations clearly indicated that Af experiences the lag and then exponential growth phase. An Af cell was observed to be attached to the surface of pyrite during the lag, implying that a direct leaching by the microbe really happens for the period. It is not certain, however, whether the main mechanism of pyrite oxidation during that time was the direct leaching or not, because there were just a few cells confirmed to be attached and most of the dissolved Fe was Fe(III). The dissolved Fe concentration stayed almost constant from the mid-lag phase to just before the onset of the exponential phase, suggesting that AI needs an adaptation time to switch its oxidation mechanism from one to the other whichever it is during that stage of growth. The moment of Af's cell division was observed by SEM on the surface of pyrite during the lag phase. The corrosion outline around the dividing cell was quite similar to the shape of the cell itself, which implies that the rate of the microbial oxidation is very uneven and the rate when the cell metabolizes should be much faster than that calculated from the concentration variation of the dissolved Fe. The number of etch holes by Af is much higher on the inoculated surfaces, indicating the average rate of pyrite oxidation is also much faster than that of abiotic oxidation. The microbial etch holes on pyrite surface are small and deep, which may influence the transition of the growth phases of Af from lag to exponential.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.853-860
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• 2012

To estimate potential use of fly ash in reducing $CH_4$ and $CO_2$ emission from soil, $CH_4$ and $CO_2$ fluxes from a paddy soil mixed with fly ash at different rate (w/w; 0, 5, and 10%) in the presence and absence of fertilizer N ($(NH_4)_2SO_4$) addition were investigated in a laboratory incubation for 60 days under changing water regime from wetting to drying via transition. The mean $CH_4$ flux during the entire incubation period ranged from 0.59 to $1.68mg\;CH_4\;m^{-2}day^{-1}$ with a lower rate in the soil treated with N fertilizer due to suppression of $CH_4$ production by $SO_4^{2-}$ that acts as an electron acceptor, leading to decreases in electron availability for methanogen. Fly ash application reduced $CH_4$ flux by 37.5 and 33.0% in soils without and with N addition, respectively, probably due to retardation of $CH_4$ diffusion through soil pores by addition of fine-textured fly ash. In addition, as fly ash has a potential for $CO_2$ removal via carbonation (formation of carbonate precipitates) that decreases $CO_2$ availability that is a substrate for $CO_2$ reduction reaction (one of $CH_4$ generation pathways) is likely to be another mechanisms of $CH_4$ flux reduction by fly ash. Meanwhile, the mean $CO_2$ flux during the entire incubation period was between 0.64 and $0.90g\;CO_2\;m^{-2}day^{-1}$, and that of N treated soil was lower than that without N addition. Because N addition is likely to increase soil respiration, it is not straightforward to explain the results. However, it may be possible that our experiment did not account for the substantial amount of $CO_2$ produced by heterotrophs that were activated by N addition in earlier period than the measurement was initiated. Fly ash application also lowered $CO_2$ flux by up to 20% in the soil mixed with fly ash at 10% through $CO_2$ removal by the carbonation. At the whole picture, fly ash application at 10% decreased global warming potential of emitted $CH_4$ and $CO_2$ by about 20%. Therefore, our results suggest that fly ash application can be a soil management practice to reduce green house gas emission from paddy soils. Further studies under field conditions with rice cultivation are necessary to verify our findings.

• Journal of the Korean Vacuum Society
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• v.14 no.2
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• pp.78-83
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• 2005

Nanometric crystalline silicon (no-Si) embedded in dielectric medium has been paid attention as an efficient light emitting center for more than a decade. In nc-Si, excitonic electron-hole pairs are considered to attribute to radiative recombination. However the surface defects surrounding no-Si is one of non-radiative decay paths competing with the radiative band edge transition, ultimately which makes the emission efficiency of no-Si very poor. In order to passivate those defects - dangling bonds in the $Si:SiO_2$ interface, hydrogen is usually utilized. The luminescence yield from no-Si is dramatically enhanced by defect termination. However due to relatively high mobility of hydrogen in a matrix, hydrogen-terminated no-Si may no longer sustain the enhancement effect on subsequent thermal processes. Therefore instead of easily reversible hydrogen, phosphorus was introduced by ion implantation, expecting to have the same enhancement effect and to be more resistive against succeeding thermal treatments. Samples were Prepared by 400 keV Si implantation with doses of $1\times10^{17}\;Si/cm^2$ and by multi-energy Phosphorus implantation to make relatively uniform phosphorus concentration in the region where implanted Si ions are distributed. Crystalline silicon was precipitated by annealing at $1,100^{\circ}C$ for 2 hours in Ar environment and subsequent annealing were performed for an hour in Ar at a few temperature stages up to $1,000^{\circ}C$ to show improved thermal resistance. Experimental data such as enhancement effect of PL yield, decay time, peak shift for the phosphorus implanted nc-Si are shown, and the possible mechanisms are discussed as well.

• Journal of the Korean Vacuum Society
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• v.18 no.6
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• pp.459-467
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• 2009

$Cd_2GeSe_4$ and $Cd_2GeSe_4:Co^{2+}$ films were prepared on indium-tin-oxide(ITO)-coated glass substrates by using thermal evaporation. The crystallization was achieved by annealing the as-deposited films in flowing nitrogen. X-ray diffraction spectra showed that the $Cd_2GeSe_4$ and the $Cd_2GeSe_4:Co^{2+}$ films were preferentially grown along the (113) orientation. The crystal structure was rhomohedral(hexagonal) with lattice constants of $a=7.405\;{\AA}$ and $c=36.240\;{\AA}$ for $Cd_2GeSe_4$ and $a=7.43\;{\AA}$ and $c=36.81\;{\AA}$ for $Cd_2GeSe_4:Co^{2+}$ films. From the scanning electron microscope images, the $Cd_2GeSe_4$ and $Cd_2GeSe_4:Co^{2+}$ films were plated, and the grain size increased with increasing annealing temperature. The optical energy band gap, measured at room temperature, of the as-deposited $Cd_2GeSe_4$ films was 1.70 eV and increased to about 1.74 eV and of the as-deposited $Cd_2GeSe_4:Co^{2+}$ films was 1.79 eV and decreased to about 1.74 eV upon annealing in flowing nitrogen at temperatures from $200^{\circ}C$ to $500^{\circ}C$. The dynamical behavior of the charge carriers in the $Cd_2GeSe_4$ and $Cd_2GeSe_4:Co^{2+}$ films were investigated by using the photoinduced discharge characteristics technique.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1164-1170
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• 1999

The physicochemical characteristics of ${\beta}-glucan$ isolated from waxy and non-waxy barley were investigated. The hull-less waxy and non-waxy barley containing 6.5% and 5.3% of total ${\beta}-glucan$ respectively, were used as a starting material. The yield and ${\beta}-glucan$ content of crude ${\beta}-glucan$ from waxy barley was 5.54% and 62.9%, respectively, and those were higher than 3.34% and 59.2% from non-waxy barley. The crude ${\beta}-glucan$ purified with selective precipitation and enzymatic treatment to obtain the ${\beta}-glucan$ isolate of high purity (>99%). The total yield of purified ${\beta}-glucan$ from waxy and non-waxy barley was 4.46% and 2.59%, respectively. The surface appearance of the purified ${\beta}-glucan$ by scanning electron microscopy (SEM) showed randomly entangled multi-net structure of ${\beta}-glucan$ microfibrils. The melting temperature of ${\beta}-glucan$ from waxy and non-waxy barley measured by differential scanning calorimetry (DSC) was $184.6^{\circ}C$, and $180.3^{\circ}C$, respectively. DSC endotherm of ${\beta}-glucan$ solution showed 2 peaks near $68^{\circ}C$ and $84^{\circ}C$. Enthalpy of phase transition was higher in non-waxy ${\beta}-glucan$ than waxy ${\beta}-glucan$, and the intrinsic viscosity of ${\beta}-glucan$ solution from waxy barley was higher than that of non-waxy ${\beta}-glucan$. The pasting viscosity of barley starch with the purified ${\beta}-glucan$ determined by Rapid Visco-Analyzer was higher than that of barley starch without ${\beta}-glucan$, and the effect of ${\beta}-glucan$ on increasing the paste viscosity was greater in non-waxy barley starch.

• Journal of the Mineralogical Society of Korea
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• v.6 no.1
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• pp.1-16
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• 1993

The chemical and optical absorption spectroscopic characters of pink and colorless tourmalines from San Diego mine in California, U.S.A., blue/green tourmalines from anonymous mine, Brazil, and brownis black tourmalines from Uncheon and Haksan mines in Korea have been studied using X-ray diffractometer, electron microprobe, optical absorption spectroscopy, and heat treatment. Least-squares refinements give unit cell diminsions : a = 15.96-16.01 ${\AA}$, c = 7.15-7.16 ${\AA}$ for the brownish black tourmalines, a = 15.82 - 15.87 ${\AA}$, c = 7.09 - 7.10 ${\AA}$ for pink tourmalines, and a = 15.88 - 15.94 ${\AA}$, c = 7.12 - 7.15 ${\AA}$ for blue green tourmalines. The colors of tourmalines are responsible for the transition elements. The pink color is attributed to the $Mn^{3+}$ ions, the blue-green to $Fe^{2+}$ and $Mn^{2+}$, bluish green to $Cu^{2+}$, and the brownish black to $Fe^{2+}$, $Fe^{2+}$ - $Fe^{3+}$, and $Fe^{2+}$ - $Ti^{4+}$. The $Mn^{3+}$ ions of pink color tourmalines are stabilized in the Y sites compressed along the O(1)H-O(3)H axis by Jahn-Teller distortion. Heating removes the pink or red component from tourmalines, producing the colorless stones from the pink and red ones. The bluish green samples change into the greenish blue ones and a certain yellowish green samples change into the light green ones by heat treatment. In the elbaite-schorl series, the concentration of Fe and Mn are variable depending on the color zones. The green zone is characterrized by the high content of Fe and Mn are variable depending on the color zones. The green zone is characterized by the high content of Fe, whereas the pink zone by the high content of Mn. Mn increases in deep yellow zone compared with yellow or colorless zones.

• Economic and Environmental Geology
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• v.54 no.6
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• pp.671-687
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• 2021

This study investigated the firing temperature and thermal deformation process of roof tiles excavated from the connected stone-mound tomb in Seokchon-dong, Seoul, based on mineralogical and physical properties. A large number of roof tiles were excavated from the tomb site and some roof tiles were deformed by heat and were fired in uneven conditions. The colors of original roof tiles and their cores are mostly yellowish-brown, with high water absorption over 12%, containing fine-grained textures and some minerals such as quartz, feldspars, amphibole, and mica. It is estimated that the original roof tiles were fired below 900℃ in oxidation condition, showing loose matrices and mica layers by scanning electron microscopy. However, deformed roof tiles have the uneven surface color of reddish-brown and bluish-gray, and those cross-sections have sandwich structures in which dense reddish-brown surface and porous grey core coexist. They contained mullite and hercynite, so it was estimated to have been fired over 1,000℃, with 0.81~11% water absorption. In some samples, bloating pores by overfiring were observed, which means that they were fired at more than 1,200℃. In addition, the refirng experiments that the original roof tile was fired between 800℃ and 1,200℃ were carried out to investigate the physical and mineralogical properties of roof tiles compared to deformed ones. As a result, the water absorption decreased rapidly and the mineral phase started to change over 1,000℃. As the temperature gradually rises, the matrices are partially melted and recrystallized, resulting in similar thermal characteristics of deformed roof tiles. Therefore, the roof tiles from ancient tombs in Seokchon-dong seem to experience the secondary high temperature of 1,000 to 1,200℃ under uneven firing conditions, resulting in deformation characteristics such as shape transformation and mineral phase transition. It is considered to have been related to cremation rituals at the tombs of Seockchon-dong during the Baekje period.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.48 no.1
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• pp.55-64
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• 2022

The potassium cream soap with fatty acid called cleaning foam has a crystal gel structure, and unlike an emulsion system, it is weak to shear stress and shows characteristics that are easily separated under high temperature storage conditions. The crystal gel structure of cleansing foams is significantly influenced by the nature and proportion of fatty acids, degree of neutralization, and the nature and proportion of polyols. In order to investigate the effect of these parameters on the crystal gel structure, a ternary system consisting of water/KOH/fatty acid was investigated in this study. The investigation of differential scanning calorimeter (DSC) revealed that the eutectic point was found at the ratio of myristic acid (MA) : stearic acid (SA) = 3 : 1 and ternary systems were the most stable at the eutectic point. However, the increase in fatty acid content had little effect on stability. On the basis of viscosity and polarized optical microscopy (POM) measurements, the optimum degree of neutralization was found to be about 75%. The system was stable when the melting point (T_m) of the ternary system was higher than the storage temperature and the crystal phase was transferred to lamellar gel phase, but the increase in fatty acid content had little effect on stability. The addition of polyols to the ternary system played an important role in changing the T_m and causing phase transition. The structure of the cleansing foams were confirmed through cryogenic scanning electron microscope (Cryo-SEM), small and wide angle X-ray scattering (SAXS and WAXS) analysis. Since butylene glycol (BG), propylene glycol (PG), and dipropylene glycol (DPG) lowered the T_m and hindered the lamellar gel formation, they were unsuitable for the formation of stable cleansing foam. In contrast, glycerin, PEG-400, and sorbitol increased the T_m, and facilitated the formation of lamellar gel phase, which led to a stable ternary system. Glycerin was found to be the most optimal agent to prepare a cleansing foam with enhanced stability.