• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.178-178
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• 2016

Every display is equipped with a cover glass to protect the underneath displaying devices from mechanical and environmental impact during its use. The strengthened glass such as Gorilla glass.$^{TM}$ has been exclusively adopted as a cover glass in many displays. Conventionally, the strengthened glass has been manufactured via ion-exchange process in wet salt bath at high temperature of around $500^{\circ}C$ for hours of treatment time. During ion-exchange process, Na ions with smaller diameter are substituted with larger-diameter K ions, resulting in high compressive stress in near-surface region and making the treated glass very resistant to scratch or impact during its use. In this study, PIIID (plasma immersion ion implantation and deposition) technique was used to implant metal ions into the glass surface for strengthening. In addition, due to the plasmonic effect of the implanted metal ions, the metal-ion implanted glass samples got colored. To implant metal ions, plasma immersion ion implantation technique combined with HiPIMS method was adopted. The HiPIMS pulse voltage of up to 1.4 kV was applied to the 3" magnetron sputtering targets (Cu, Ag, Au, Al). At the same time, the sample stage with glass samples was synchronously pulse-biased via -50 kV high voltage pulse modulator. The frequency and pulse width of 100 Hz and 15 usec, respectively, were used during metal ion implantation. In addition, nitrogen ions were implanted to study the strengthening effect of gas ion implantation. The mechanical and optical properties of implanted glass samples were investigated using micro-hardness tester and UV-Vis spectrometer. The implanted ion distribution and the chemical states along depth was studied with XPS (X-ray photo-electron spectroscopy). A cross-sectional TEM study was also conducted to investigate the nature of implanted metal ions. The ion-implanted glass samples showed increased hardness of ~1.5 times at short implantation times. However, with increasing the implantation time, the surface hardness was decreased due to the accumulation of implantation damage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.52-52
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• 2009

To date, chalcogenide alloy such as $Ge_2Sb_2Te_5$(GST) have not only been rigorously studied for use in Phase Change Random Access Memory(PRAM) applications, but also temperature gap to make different states is not enough to apply to device between amorphous and crystalline state. In this study, we have investigated a new system of phase change media based on the In-Sb-Te(IST) ternary alloys for PRAM. IST chalcogenide thin films were prepared in trench structure (aspect ratio 5:1 of length=500nm, width=100nm) using Tri methyl Indium $(In(CH_3)_4$), $Sb(iPr)_3$ $(Sb(C_3H_7)_3)$ and $Te(iPr)_2(Te(C_3H_7)_2)$ precursors. MOCVD process is very powerful system to deposit in ultra integrated device like 100nm scaled trench structure. And IST materials for PRAM can be grown at low deposition temperature below $200^{\circ}C$ in comparison with GST materials. Although Melting temperature of 1ST materials was $\sim 630^{\circ}C$ like GST, Crystalline temperature of them was ~$290^{\circ}C$; one of GST were $130^{\circ}C$. In-Sb-Te materials will be good candidate materials for PRAM applications. And MOCVD system is powerful for applying ultra scale integration cell.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.186-193
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• 2006

In this study, we analyzed the electrical and optical properties of metalorganic chemical vapor deposition grown InGaAs/InGaAsP/InP quantum dot(QD) molecules by using photoluminescence and deep-level transient spectroscopy. From these resulte, the energy levels of the large QDs are located at deeper region from the conduction band edge of the barrier than that of the small QDs, The large QDs seem to have the energy states more than two, and these energy levels of the QD molecules are located at 0.35, 0.42, and 0.45 eV from conduction band edge under -4 V reverse bias conditions. The energy levels are closely coupled under low reverse bias, and then decoupled as the bias voltage is increased.

• Genomics & Informatics
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• v.13 no.1
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• pp.15-24
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• 2015

Fatty acid synthase (FASN, EC 2.3.1.85), is a multi-enzyme dimer complex that plays a critical role in lipogenesis. This lipogenic enzyme has gained importance beyond its physiological role due to its implications in several clinical conditions-cancers, obesity, and diabetes. This has made FASN an attractive pharmacological target. Here, we have attempted to predict the theoretical models for the human enoyl reductase (ER) and ${\beta}$-ketoacyl reductase (KR) domains based on the porcine FASN crystal structure, which was the structurally closest template available at the time of this study. Comparative modeling methods were used for studying the structure-function relationships. Different validation studies revealed the predicted structures to be highly plausible. The respective substrates of ER and KR domains-namely, trans-butenoyl and ${\beta}$-ketobutyryl-were computationally docked into active sites using Glide in order to understand the probable binding mode. The molecular dynamics simulations of the apo and holo states of ER and KR showed stable backbone root mean square deviation trajectories with minimal deviation. Ramachandran plot analysis showed 96.0% of residues in the most favorable region for ER and 90.3% for the KR domain, respectively. Thus, the predicted models yielded significant insights into the substrate binding modes of the ER and KR catalytic domains and will aid in identifying novel chemical inhibitors of human FASN that target these domains.

• Journal of The Korean Association For Science Education
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• v.24 no.2
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• pp.287-297
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• 2004

In this study, students' understanding of the analogies used for chemical concepts in science textbooks, misconceptions induced by the analogy, and the factors affecting conceptual understanding were investigated. In addition to the tests of field independency and logical thinking ability, tests of students' understanding of concepts and analogies on three states of matter, pressure-volume relation, molecular motion, and changing state depending upon energy were administered. The results revealed that half of the subjects understood the analogies differently from the textbook writers' intention and that students' conceptual understanding was significantly correlated with the degree of understanding on corresponding analogies, field independency, logical thinking ability, and prior achievement of science. The results of analyzing the direct and indirect effects of each variable on conceptual understanding showed that the direct effect of prior achievement was significant and that field independency and logical thinking ability had indirect effects through understanding of analogies and prior achievement of science. The limitations and implications of using analogies in science education were discussed on the basis of the results.

• Journal of environmental and Sanitary engineering
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• v.17 no.2
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• pp.71-78
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• 2002

This study was conducted to evaluate the concentration distribution characteristics of air pollutants by the yellow sand from China. The concentrations and chemical properties of FPM contained in the yellow sand were compared with those of air pollutants when having no yellow sand in order to estimate the variation characteristics and the originated source of air pollutants moved by yellow sand. The concentrations of PM-2.5 and PM-10 contained in the yellow sand showed an increase of 2.3 to 2.7 times than usual, and the concentrations of NO2 and SO2 in the gaseous pollutants showed an increase of about 1.6 times by yellow sand, and thus the air contamination was much influenced by yellow sand phenomenon. The concentrations of inorganic elements contained in FPM from the yellow sand showed a higher concentration variation in the order of Al>Mg>Zn>Pb than usual. The concentration coefficient of air aerosol during the yellow sand period showed that Na, K, Ca, Mg and Fe were originated from natural source, and Pb, Cr, Cd, Cu and Zn were originated from artificial source for inorganic elements. The correlation analysis between FPM and inorganic elements showed in the descending order of Al>K>Pb>Mg, and thus the deposited amount of Pb was influenced by that of yellow sand. The average concentrations of PM-10 measured during the yellow sand period exceeded the Korea Air Environmental Standard and showed a excess rate of 3.4 times in the maximum but the average concentrations of PM-2.5 showed within the United States Air Environmental Standard.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.87-92
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• 2001

Magnetic Fe-Co(C) nanocapsules and Fe-Co nanoparticles were prepared by arc-discharge in two kinds of atmospheres, i.e. methane and a mixture of ($H_2$+Ar), respectively. Characterization and magnetic properties of this two kinds of ultrafine particles were investigated systematically by means of X-ray diffraction, Mssbauer spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, energy disperse spectroscopy analysis, chemical analysis, oxygen determination and magnetization measurement. Effects of carbon element, decomposed from a methane atmosphere in carbon arc process, on phase structures, magnetic states and surface characterization were studied in comparison to that of Ar element. Two ultrafine particles showed a little difference in the weight ratio of (Fe/co) and the size for Fe-Co nanoparticles was about two times bigger than Fe-Co(C) nanocapsules. The saturation magnetization of Fe-Co (C) nanocapsules was about 8% higher than that of Fe-Co nanoparticles while their phase constitutions were similar. Although no carbon could be detected by XRD measurement because of extremely thin shells on the surfaces of the cores, it is still believed that they are carbon and oxygen layers.

• Korean Journal of Materials Research
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• v.26 no.5
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• pp.258-265
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• 2016

Fluorine-doped tin oxide (FTO) nanoparticles have been successfully synthesized using ultrasonic spray pyrolysis. The morphologies, crystal structures, chemical bonding states, and electrochemical properties of the nanoparticles are investigated. The FTO nanoparticles show uniform morphology and size distribution in the range of 6-10 nm. The FTO nanoparticles exhibit excellent electrochemical performance with high discharge specific capacity and good cycling stability ($620mAhg^{-1}$ capacity retention up to 50 cycles), as well as excellent high-rate performance ($250mAhg^{-1}$ at $700mAg^{-1}$) compared to that of commercial $SnO_2$. The improved electrochemical performance can be explained by two main effects. First, the excellent cycling stability with high discharge capacity is attributed to the nano-sized FTO particles, which are related to the increased electrochemical active area between the electrode and electrolyte. Second, the superb high-rate performance and the excellent cycling stability are ascribed to the increased electrical conductivity, which results from the introduction of fluorine doping in $SnO_2$. This noble electrode structure can provide powerful potential anode materials for high-performance lithiumion batteries.

• Korean Journal of Materials Research
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• v.26 no.5
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• pp.250-257
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• 2016

Octahedral $Co_3O_4$/carbon nanofiber (CNF) composites are fabricated using electrospinning and hydrothermal methods. Their morphological characteristics, chemical bonding states, and electrochemical properties are used to demonstrate the improved photovoltaic properties of the samples. Octahedral $Co_3O_4$ grown on CNFs is based on metallic Co nanoparticles acting as seeds in the CNFs, which seeds are directly related to the high performance of DSSCs. The octahedral $Co_3O_4$/CNFs composites exhibit high photocurrent density ($12.73mA/m^2$), superb fill factor (62.1 %), and excellent power conversion efficiency (5.61 %) compared to those characteristics of commercial $Co_3O_4$, conventional CNFs, and metallic Co-seed/CNFs. These results can be described as stemmnig from the synergistic effect of the porous and graphitized matrix formed by catalytic graphitization using the metal cobalt catalyst on CNFs, which leads to an increase in the catalytic activity for the reduction of triiodide ions. Therefore, octahedral $Co_3O_4$/CNFs composites can be used as a counter electrode for Pt-free dye-sensitized solar cells.

• Korean Journal of Materials Research
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• v.21 no.2
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• pp.120-124
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• 2011

Silicon heterojunction solar cells have been studied by many research groups. In this work, silicon heterojunction solar cells having a simple structure of Ag/ZnO:Al/n type a-Si:H/p type c-Si/Al were fabricated. Samples were fabricated to investigate the effect of transparent conductive oxide growth conditions on the interface between ZnO:Al layer and a-Si:H layer. One sample was deposited by ZnO:Al at low working pressure. The other sample was deposited by ZnO:Al at alternating high working pressure and low working pressure. Electrical properties and chemical properties were investigated by light I-V characteristics and AES method, respectively. The light I-V characteristics showed better efficiency on sample deposited by ZnO:Al by alternating high working pressure and low working pressure. Atomic concentrations and relative oxidation states of Si, O, and Zn were analyzed by AES method. For poor efficiency samples, Si was diffused into ZnO:Al layer and O was diffused at the interface of ZnO:Al and Si. Differentiated O KLL spectra, Zn LMM spectra, and Si KLL spectra were used for interface reaction and oxidation state. According to AES spectra, sample deposited by high working pressure was effective at reducing the interface reaction and the Si diffusion. Consequently, the efficiency was improved by suppressing the SiOx formation at the interface.