• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.81-81
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• 1999

고에너지 이온 주입에 의해 형성되는 결함의 거동을 DLTS(deep level transient spectroscopy)를 통해 조사하였다. 이온 주입에 이용된 기판들은 서로 다른 산소 농도를 가지고 있었으며, B 이온의 주입 농도는 각각 5X10E13 ~ 4X10E14으로 주입 에너지는 1.5MeV였다. 이온 주입에 의해 형성된 buried layer 내의 boron의 농도는 SIMS(secondary ion mass spectroscopy)를 이용하여 측정하였으며, 열처리에 따른 이차 결함의 생성은 TEM(transmission electron microscopy) 및 BMD(bulk micro defect)를 조사함으로써 알 수 있었다. 이온 주입에 의해 형성된 일차 결함의 제거 및 silicon 내부에서의 금속 gettering을 위하여 furnace 및 RTA (rapid thermal annealing)를 이용한 열처리를 행하였다. 이온주입 초기 상태 및 산소의 농도 또는 이온주입의 농도에 따른 결함을 살펴보기 위하여 DLTS를 이용하였으며, 또한 열처리에 따른 이러한 초기 결함들의 거동을 조사하여 TEM 및 BMD 결과와 비교, 분석하였다.

• Journal of the Korean Chemical Society
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• v.13 no.3
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• pp.195-198
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• 1969

Determination of partial molal volumes of anilinium chloride isopropanol-water mixtures at 30.00$^{\circ}$showed a distinct minimum at 0.20 mole fraction isopropanol. This was interpreted as maximum in electrostriction effect and minimum in water structure. The depth in $\bar{V}^{\circ}$for alcohol-water mixtures was in the order MeOH > i-PrOH > EtOH, which indicated the importance of microscopic structure around ions.

• Bulletin of the Korean Chemical Society
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• v.18 no.4
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• pp.406-409
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• 1997

The various cobalt(Ⅱ) complexes were synthesized and characterized using tris-(2-benzimidazolylmethyl)amine (ntb) as a ligand where the ntb plays as a tripodal tetradentate ligand to form complexes with a trigonal pyramidal geometry. The complexes have 5 and 6 coordinate cobalt(Ⅱ) ions depending on the additional ligand used. In each complex the additional ligand, chloride anion, or acetate anion occupies the "open" site trans to the apical tertiary nitrogen atom of ntb ligand. Complex 1, [Co(Ⅱ)(ntb)Cl]Cl has a trigonal bipyramidal geometry. This geometry was easily constructed using ntb as a tetradentate ligand and chloride as a monodentate ligand. The complex is isostructural to the corresponding manganese(Ⅱ) complex. Crystal data are as follows: [Co(Ⅱ)(ntb)Cl]Cl·MeOH, 1. triclinic space group P1; a=13.524(2) Å, b=14.037(2) Å, c=17.275(1) Å; α=78.798(9), β=84.159(8)°, γ=65.504(9)°; V=2929.6(6) Å3; Z=4; R1=0.0715, wR2=0.1461 for reflections of I > 2σ(I). Six coordinate complex 2 [Co(ntb)(OAc)](OAc) was synthesized using ntb as a tetradentate ligand and acetate as a bidentate chelating ligand.

• The Korean Journal of Pesticide Science
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• v.16 no.4
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• pp.267-272
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• 2012

Vitex trifolia L. is a full grown fruit of Vitex rotundifolia L. (Verbenaceae). It has been used for treating headache, dizziness, toothache and removal of fever as a traditional medicine in Korea. V. trifolia (500 g) were extracted three times with 80% aqueous MeOH at room temperature. The MeOH extract (38 g) was successively partitioned with n-hexane, EtOAc, n-BuOH and $H_2O$. Both n-hexane and EtOAc fractions showed more than 80% antifungal activity in vivo against several plant pathogens at 2000 ppm. Successive repeated silica gel, Sephadex LH-20, preparative TLC, and preparative HPLC of these fractions led to isolation of three compounds. Using mainly mass spectroscopy and nuclear magnatic resonance (NMR) spectroscopy, their chemical structures were determined as agnuside(1), chrysosplenol B(2), and artemetin(3). Compound 2 was isolated for the first time from V. trifolia. Study on in vitro and in vivo antifungal activities of the isolated compounds is in progress.

• Journal of Korean Society of Forest Science
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• v.95 no.4
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• pp.429-434
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• 2006

The dried needles (1.5 kg) of Picea abies Karsten were ground, extracted with acetone-$H_2O$ (7:3, v/v), concentrated, and fractionated with a series of n-hexane, methylene chloride, ethyl acetate and water on a separatory funnel. Each fraction was freeze dried, then a portion of ethyl acetate soluble powder was chromatographed on a Sephadex LH-20 column using a series of aqueous methanol and ethanol-n-hexane mixture as eluents. The isolated compounds were identified by cellulose TLC, $^1H$-, $^{13}C$-NMR, FAB and EI-MS. (+)-catechin (compound I), (-)-epicatechin (compound II), kaempferol-3-O-${\beta}$-D-glucopyranoside (compound III), 4-hydroxyacetophenone (compound IV) were isolated from the ethyl acetate soluble fraction and (+)-catechin (compound I), protocatechuic acid (compound V) were isolated from the $H_2O$ soluble fraction of P. abies needle. The antioxidative activities of each fraction and the isolated compounds were tested by DPPH radical scavenging method, and EtOAc soluble fraction, (+)-catechin and (-)-epicatechin showed similar values to ${\alpha}$-tocopherol and BHT as controls.

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.639-643
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• 2011

Zinc oxide as an optoelectronic device material was studied to utilize its wide band gap of 3.37 eV and high exciton biding energy of 60 meV. Using anti-site nitrogen to generate p-type zinc oxide has shown a deep acceptor level and low solubility. To increase the nitrogen solubility in zinc oxide, group 13 elements (aluminum, gallium, and indium) was co-added to nitrogen. The effect of aluminum on nitrogen solubility in a $3{\times}3{\times}2$ zinc oxide super cell containing 72 atoms was investigated using density functional theory with hybrid functionals of Heyd, Scuseria, and Ernzerhof (HSE). Aluminum and nitrogen were substituted for zinc and oxygen sites in the super cell, respectively. The band gap of the undoped super cell was calculated to be 3.36 eV from the density of states, and was in good agreement with the experimentally obtained value. Formation energies of a nitrogen molecule and nitric oxide in the zinc oxide super cell in zinc-rich conditions were lower than those in oxygen-rich conditions. When the number of nitrogen molecules near the aluminum increased from one to four in the super cell, their formation energies decreased to approach the valence band maximum to some degree. However, the acceptor level of nitrogen in zinc oxide with the co-incorporation of aluminum was still deep.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.336-336
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• 2012

수명 측정법과 동시 계수 도플러 넓어짐 양전자 소멸 분광법으로 p형과 n형 실리콘 시료에 0, 3.98 MeV 에너지를 가진 $0.0{\sim}20.0{\times}10^{13}$ protons/$cm^2$ 양성자 빔 조사에 의한 결함을 측정하여 실리콘 결함 특성에 대하여 조사하였다. 양전자와 전자의 쌍소멸로 발생하는 감마선 스펙트럼의 전자 밀도 에너지를 수리적 해석 방법인 S-변수와 열린 부피 결함에 대한 측정법으로서 양전자 수명 ${\tau}1$과 ${\tau}2$, 이에 따른 밀도 I1과 I2를 사용하여, 시료의 구조 변화를 측정하였다. 본 연구에서 측정된 S-변수와 양전자 수명은 시료에 조사된 양성자의 빔 에너지에 따라 변화하기보다 양성자 조사량의 변화에 따라 결함이 증가하였으며, 양전자 수명 측정과 같은 경향을 보여준다. SRIM의 결과로써, 양성자 조사 에너지에 따른 Bragg 피크 때문에 양성자는 시료의 특정 깊이에 주로 결함을 형성하여 시료 전체에는 결함으로 잘 나타나지 않기 때문이다. 빔의 조사량에 따른 결함의 영향이 더 큰 것으로 나타났다.

• Progress in Superconductivity and Cryogenics
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• v.18 no.2
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• pp.8-13
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• 2016

Superconducting properties of thin film MgB2 superconductors irradiated with 45 MeV ${\alpha}$-particle beam were studied. After the irradiation, enhancement of the critical current density and pinning force was observed, scaling close to strong pinning formula. Double logarithmic plots of the maximum pinning force density with irreversible magnetic field show a power law behavior close to carbon-doped MgB2 film or polycrystals. Variation of normalized pinning force density in the reduced magnetic field suggests scaling formulas for strong pinning mechanism like planar defects. We also observed a rapid decay of critical current density as the vortex lattice constant decreases, due to the strong interaction between vortices and increasing magnetic field.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.165-169
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• 2018

An assessment for determining N-16 activity concentrations during the operation condition of Bangladesh Atomic Energy Commission TRIGA Research Reactor was performed employing several governing equations. The radionuclide N-16 is a high energy (6.13 MeV) gamma emitter which is predominately created by the fast neutron interaction with O-16 present in the reactor core water. During reactor operation at different power level, the concentration of N-16 at the reactor bay region may increase causing radiation risk to the reactor operating personnel or the general public. Concerning the safety of the research reactor, the present study deals with the estimation of N-16 activity concentrations in the regions of reactor core, reactor tank, and reactor bay at different reactor power levels under natural convection cooling mode. The estimated N-16 activity concentration values with 500 kW reactor power at the reactor core region was $7.40{\times}10^5Bq/cm^3$ and at the bay region was $3.39{\times}10^5Bq/cm^3$. At 3 MW reactor power with active forced convection cooling mode, the N-16 activity concentration in the decay tank exit water was also determined, and the value was $4.14{\times}10^{-1}Bq/cm^3$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.187-188
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• 2005

The characteristics of GaN epitaxial layers grown on silicon (111) substrates by metalorganic vapor phase epitaxy have been investigated. The only control of AlN thickness was found to decrease the stress sufficiently for avoiding crack formation in an overgrown thick ($2.6{\mu}m$) GaN layer. X-ray diffraction and photoluminescence measurements are used to determine the effect of AlN thickness on the strain in the subsequent GaN layers. Strong band edge photoluminescence of GaN on Si(111) was observed with a full width at half maximum of the bound exciton line as low as 17meV at 13K.