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Spectroscopic Characterization of 400℃ Annealed ZnxCd1-xS Thin Films (400℃ 열처리한 삼원화합물 ZnxCd1-xS 박막의 분광학적 특성 연구)

  • Kang, Kwang-Yong;Lee, Seung-Hwan;Lee, Nam-Kwon;Lee, Jeong-Ju;Yu, Yun-Sik
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.26 no.1
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    • pp.101-112
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    • 2015
  • II~VI compound semiconductors, $Zn_xCd_{1-x}S$ thin films have been synthesized onto indium-tin-oxide(ITO) coated glass substrates using thermal evaporation technique. The composition ratio x($0{\leq}x{\leq}1$) was varied to fabricate different kinds of $Zn_xCd_{1-x}S$ thin films including CdS(x=0) and ZnS(x=1) thin films. Then, the deposited thin films were thermally annealed at $400^{\circ}C$ to enhance their crystallinity. The chemical composition and electronic structure of films were investigated by using X-ray photoelectron spectroscopy(XPS). The optical energy gaps of the samples were determined by ultra violet-visible-near infrared(UV-Vis-NIR) spectroscopy and were found to vary in the range of 2.44 to 3.98 eV when x changes from 0 to 1. Finally, we measured the THz characteristics of the $Zn_xCd_{1-x}S$ thin films using THz-TDS(time domain spectroscopy) system to identify the capability for electronic and optical devices in THz region.

Optical Characteristics of Near-monolayer InAs Quantum Dots

  • Kim, Yeong-Ho;Kim, Seong-Jun;No, Sam-Gyu;Park, Dong-U;Kim, Jin-Su;Im, In-Sik;Kim, Jong-Su
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.293-294
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    • 2011
  • It is known that semiconductor quantum-dot (QD) heterostructures have superior zero-dimensional quantum confinement, and they have been successfully applied to semiconductor laser diodes (QDLDs) for optical communication and infrared photodetectors (QDIPs) for thermal images [1]. The self-assembled QDs are normally formed at Stranski-Krastanov (S-K) growth mode utilizing the accumulated strain due to lattice-mismatch existing at heterointerfaces between QDs and cap layers. In order to increase the areal density and the number of stacks of QDs, recently, sub-monolayer (SML)-thick QDs (SQDs) with reduced strain were tried by equivalent thicknesses thinner than a wetting layer (WL) existing in conventional QDs (CQDs) by S-K mode. Despite that it is very different from CQDs with a well-defined WL, the SQD structure has been successfully applied to QDIP[2]. In this study, optical characteristics are investigated by using photoluminescence (PL) spectra taken from self-assembled InAs/GaAs QDs whose coverage are changing from submonolayer to a few monolayers. The QD structures were grown by using molecular beam epitaxy (MBE) on semi-insulating GaAs (100) substrates, and formed at a substrate temperature of 480$^{\circ}C$ followed by covering GaAs cap layer at 590$^{\circ}C$. We prepared six 10-period-stacked QD samples with different InAs coverages and thicknesses of GaAs spacer layers. In the QD coverage below WL thickness (~1.7 ML), the majority of SQDs with no WL coexisted with a small amount of CQDs with a WL, and multi-peak spectra changed to a single peak profile. A transition from SQDs to CQDs was found before and after a WL formation, and the sublevel of SQDs peaking at (1.32${\pm}$0.1) eV was much closer to the GaAs bandedge than that of CQDs (~1.2 eV). These revealed that QDs with no WL could be formed by near-ML coverage in InAs/GaAs system, and single-mode SQDs could be achieved by 1.5 ML just below WL that a strain field was entirely uniform.

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Current Status of the Synchrotron Small-Angle X-ray Scattering Station BL4C1 at the Pohang Accelerator Laboratory

  • Jorg Bolze;Kim, Jehan;Huang, Jung-Yun;Seungyu Rah;Youn, Hwa-Shik;Lee, Byeongdu;Shin, Tae-Joo;Moonhor Ree
    • Macromolecular Research
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    • v.10 no.1
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    • pp.2-12
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    • 2002
  • The small-angle X-ray scattering (SAXS) beamline BL4C1 at the 2.5 GeV storage ring of the Pohang Accelerator Laboratory (PAL) has been in its first you of operation since August 2000. During this first stage it could meet the basic requirements of the rapidly growing domestic SAXS user community, which has been carrying out measurements mainly on various polymer systems. The X-ray source is a bending magnet which produces white radiation with a critical energy of 5.5 keV. A synthetic double multilayer monochromator selects quasi-monochromatic radiation with a bandwidth of ca. 1.5%. This relatively low degree of monochromatization is sufficient for most SAXS measurements and allows a considerably higher flux at the sample as compared to monochromators using single crystals. Higher harmonics from the monochromator are rejected by reflection from a flat mirror, and a slit system is installed for collimation. A charge-coupled device (CCD) system, two one-dimensional photodiode arrays (PDA) and imaging plates (IP) are available its detectors. The overall performance of the beamline optics and of the detector systems has been checked using various standard samples. While the CCD and PDA detectors are well-suited for diffraction measurements, they give unsatisfactory data from weakly scattering samples, due to their high intrinsic noise. By using the IP system smooth scattering curves could be obtained in a wide dynamic range. In the second stage, stating from August 2001, the beamline will be upgraded with additional slits, focusing optics and gas-filled proportional detectors.

Vascular Plants Distributed in Baekdudaegan Mountains (Gitdaebaegibong~Mt. Cheonghwasan) (백두대간(깃대배기봉~청화산)에 분포하는 관속식물상)

  • Oh, Hyun-Kyung;You, Ju-Han
    • Korean Journal of Environment and Ecology
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    • v.32 no.1
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    • pp.1-22
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    • 2018
  • The purpose of this study is to provide the baseline data for conservation and management of Korean forest ecosystem by surveying and analyzing the vascular plants distributed from Gitdaebaegibong to Cheonghwasan in Baekdudaegan Mountains. The results are as follows. The numbers of vascular plants in the whole survey section were summarized as 771 taxa including 103 families, 379 genera, 623 species, 4 subspecies, 121 varieties and 23 forms. There were 377 taxa in A-section, 395 taxa in B-section, 278 taxa in C-section, 325 taxa in D-section, 534 taxa in E-section, and 406 taxa in F-section. The rare plants were 32 taxa including Megaleranthis saniculifolia, Rodgersia podophylla, Iris ensata var. spontanea, and Gastrodia elata. In IUCN Red List categories, there were 1 taxon of CR, EN, and DD each, 11 taxa of the VU, and 18 taxa of the LC. The Korean endemic plants were 26 taxa including Asarum versicolor, Clematis fusca var. coreana, Vicia chosenensis, Stewartia pseudocamellia, Carex okamotoi, and Luzula sudetica var. nipponica. The specific plants by floristic region were 143 taxa including 3 taxa of grade V, 12 taxa of grade IV, 41 taxa of grade III, 42 taxa of grade II, and 45 taxa of grade I. The naturalized plants were 41 taxa including Rumex crispus, Ailanthus altissima, Erechtites hieracifolia, Erigeron annuus, and Poa pratensis. The invasive alien plants were 4 taxa including Rumex acetocella, Sicyos angulatus, Ambrosia artemisiifolia, and Aster pilosus. The plants adaptable to climate change were 43 taxa including 14 taxa of endemic plants, 2 taxa of southern plants, and 27 taxa of northern plants.

AC impedance study on the interface between organic electrolyte and amorphous $WO_3$ thin film relating to the electrochemical intercalation of lithium (비정질 $WO_3$ 박막과 전해질 계면에서의 리튬 층간 반응의 교류 임피던스 해석)

  • Kim Byoung-Chul;Ju Jeh-Beck;Sohn Tae-Won
    • Journal of the Korean Electrochemical Society
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    • v.1 no.1
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    • pp.33-39
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    • 1998
  • To AC impedance study was performed in this study on the interfacial reaction between organic electrolyte and amorphous tungsten oxides thin film, cathodically coloring oxide, prepared by e-beam evaporation method in the 1 M $LiClO_4/PC$ organic solution. The electrochemical reactions at the interface were analyzed by the transient method and the complex impedance spectroscopy. The impedance spectrums showed that the electro-chemical intercalation of lithium cations was consisted of the following three steps; the first step, the charge transfer reaction of lithium cation at the interface between amorphous tungsten oxides thin film and the organic electrolyte, the second step, the adsorption of lithium atom on the surface of amorphous tungsten oxides thin film, and then the third step, the absorption and the diffusion of lithium atom into amorphous tungsten oxides thin layer. The bleaching and the coloring characteristics of amorphous tungsten oxides thin film were explained in terms of thermodynamic and kinetic variables, the simulated $R_{ct},\;C_{dl},\;D$ and $\sigma_{Li}$ by CNLS fitting method. Especially it was found that the limiting values of electrochromic reaction were the molar ratio of lithium, y=0.167 and the electrode potential, E=2.245 V (vs. Li).

Stress Distribution in Microvascular Anastomotic Coupler (AnaFix®) Micropins with Respect to the Fillet Radius (필렛효과에 따른 미세혈관 문합커플러(AnaFix®) 마이크로핀의 응력분포)

  • Jee, Dae-Won;Kim, Cheol-Woong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.11
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    • pp.1139-1145
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    • 2011
  • An automated anastomotic ring-pin system consisting of both the anastomotic ring-pin system and the coupler device has eliminated the drawbacks of the suture method. High density polyethylene (HDPE), a material with outstanding biocompatibility and injection molding capability, was used in the ring. SUS316 stainless steel, Ti-6Al-4Nb, Ti-6Al-4V, and unalloyed titanium were used in FEM simulations of the micropin. The authors categorized the microvascular anastomotic ring micropins into short neck (SN) and long neck (LN) groups in order to evaluate the effect of the micropin's fillet radius and neck length on the von Mises stress. The micropins were further divided into those with and without fillet. On the basis of the fillet radius rate (FRR), which represents the rate of change in the von Mises stress with respect to the availability and shape of the fillet, and the neck length rate (NLR), which represents the rate of change in the von Mises stress with respect to changes in the length of the neck within the fillet shape, it can be concluded that the SN-3 neck design is the most stable.

Nano Capsulization of Ceramide and the Efficacy of Atopy Skin (나노세라마이드의 캡슐화와 아토피 피부의 치료)

  • Zhoh Choon-Koo;Kim In-Young;Lee Hee-Seob
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.30 no.3 s.47
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    • pp.419-426
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    • 2004
  • The nano-ceramide capsulation is a technique that capsulates ceramide III and tocopheryl linoleate at the mono-vesicle to act on the horny layer in skin. In this technique, $0.5{\~}5.0\;wt\%$ of hydrogenated lecithin and $0.01{\~}2.00\;wt\%$ of lysolecithin are used as the membrane-strengthen agents of the mono-vesicle and $5.0{\~}10.0\;wt\%$ of propylene glycol and $5.0{\~}10.0\;wt\%$ of ethyl alcohol are used as solvents. Active ingredients such ceramide III and tocopheryl linoleate are utilized to enhance the moisturizing efficacy and treat atopy skin. These materials do not contain synthetic emulsifiers. The optimal conditions or nano-ceramide capsulation are such that particles pass Microfludizdizer 3 times at 1,000 bar and $60{\~}70^{\circ}C$ and pH of nano capsules is $5.8{\pm}0.5.$ The average size of particles is $63.1{\pm}7.34\;nm$ showing lucid state like water by the laser light scattering. A zeta potential value is $-55.1\pm0.84\;mV.$ Through clinical tests, the moisturizing effect (in-vivo, n=8, p-value<0.05) showed $21.15\%$ of improvement comparison to comparison-samples and $36.31\%$ of improvement compared to the state before treatment. Moreover, the effectiveness of atopy skin showed positive reaction from 10 volunteers.

Effect of $Al^{3+}$ Dopant on the Electrochemical Characteristics Of Spinel-type $Li_{4}Ti_{5}O_{12}$ (스피넬형 $Li_{4}Ti_{5}O_{12}$ 음극물질의 $Al^{3+}$ 첨가에 의한 전기화학적 성능 변화)

  • Jeong, Choong-Hoon;Lee, Eui-Kyung;Bang, Jong-Min;Lee, Bong-Hee;Cho, Byung-Won;Na, Byung-Ki
    • Clean Technology
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    • v.14 no.3
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    • pp.171-175
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    • 2008
  • The effect of the addition of $Al^{3+}$ dopant on the electrochemical characteristics of $Li_{4}Ti_{5}O_{12}$ was investigated. $Li_{4}Ti_{5}O_{12}$ is known as a 2ero-strain material, and $Li_{3.95}Al_{0.15}Ti_{4.9}O_{12}$ has been manufactured by solid-state reaction with high energy ball milling (HEBM). The samples were heated at 800, 900 and $1000^{\circ}C$ in electric furnace. The structural and surface structures were measured by XRD (X-ray diffraction) and SEM (scanning electron microscopy). Cut-off voltage of charge/discharge cycles was $1.0{\sim}3.0 V$ to investigate reversible capacity, cycle stability and plateau voltage. The reversible capacity of $Li_{3.95}Al_{0.15}Ti_{4.9}O_{12}$ was 138 mAh/g.

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Preparation of Zinc Oxide Thin Film by CFR Method and its Electrical Property for Detection of Sulfur Compounds (CFR 법에 의한 산화아연 박막의 제조 및 황 화합물 검출을 위한 전기적 특성)

  • Lee, Sun Yi;Park, No-Kuk;Yoon, Suk Hoon;Lee, Tae Jin
    • Korean Chemical Engineering Research
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    • v.48 no.2
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    • pp.218-223
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    • 2010
  • The zinc oxide thin film, which can be applied as the gas sensor of a semiconductor type, was grown on the silicon substrate by CFR(continuous flow reaction) method in this study. The growth property and the electrical property of the zinc oxide thin films synthesized by CFR method were also investigated. Zinc acetate solutions of 0.005~0.02 M were used as the precursor for the preparation of zinc oxide thin films. The size of ZnO particles consisted on the zinc oxide thin film increased not only with increasing concentration of precursor, but also the thickness of thin film increased. The growth rate of zinc oxide thin film by CFR method was proportionably depend on the concentration of precursor and the uniform ZnO thin film was prepared when zinc acetate of 0.01 M is used as the precursor. The charged currents on the zinc oxide thin films were obtained as its electrical property by I-V meter, and increased agree with increasing the thickness of zinc oxide thin film. Thus, it was concluded that the charged current on the zinc oxide thin film can be controlled with changing concentration of precursor solution in CFR method. The charged currents on the zinc oxide thin films also decreased when ZnO thin film is exposed under hydrogen sulfide of 500 ppmv at $300^{\circ}C$ for 5 min. From these results, it could be confirmed that the zinc oxide thin film prepared by CFR method can be used for the detection of sulfur compounds.

Termite Resistance of The Less Known Tropical Woods Species Grown in West Java, Indonesia

  • Febrianto, Fauzi;Pranata, Andi Zaim;Septiana, Dea;Arinana, Arinana;Gumilang, Adiyantara;Hidayat, Wahyu;Jang, Jae-Hyuk;Lee, Seung-Hwan;Hwang, Won-Joung;Kim, Nam-Hun
    • Journal of the Korean Wood Science and Technology
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    • v.43 no.2
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    • pp.248-257
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    • 2015
  • This research focused on the natural durability of twenty one lesser known tropical wood species planted in West Java, Indonesia against subterranean termite (Coptotermes curvignathus). It was observed that both heartwood and sapwood of Kiara payung (Filicium decipiens); heartwoods of Nangka (Arthocarpus heterophyllus), Mahoni (Swietenia macrophylla) and Simpur (Dillenia grandifolia); and sapwood of Bungur (Lagerstroemia speciosa) were rated as resistant (natural durability class II) according to Indonesian standard SNI 01.7207.2006 (BSN 2006). Both heartwood and sapwood of Salam (Syzigium polyanthum), Pasang (Lithocarpus sundaicus), Bisbul (Diospyros discolor), Rukam (Flacourtia rukam) and Trembesi (Samanea saman); heartwood of Puspa (Schima walichii), Bungur, Tanjung (Mimusops elangi) and Angsana (Pterocarpus indicus) were rated as moderately resistant (natural durability class III). Both heartwood and sapwood of Sungkai (Peronema canescens), Pine (Pinus merkusii), Mangium (Acacia mangium) and Afrika (Maesopsis eminii); sapwoods of Mahoni, Puspa and Tanjung were rated as poorly resistant (natural durability class IV). Both heartwood and sapwood of Agathis (Agathis dammara), Durian (Durio zibethinus), Ki sampang (Evodia latifolia) and Jabon (Anthocephalus cadamba); sapwoods of Nangka and Angsana were rated as very poorly resistant (natural durability class V). This reserach showed that woods with lower resistance against C. curvignathus attack (natural durability class IV and V) tend to have lower termite mortality values compared to woods with higher resistance against C. curvignathus attack (natural durability class II and III). Results of the study will provide some valuable information on termite resistance of twenty one lesser known tropical wood species planted in Indonesia.