• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.377-382
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• 2012

CdS thin films have been widely used as a buffer layer of CIGS semiconductor solar cells to reduce the lattice mismatch between transparent electrode and absorber layer. In order to prepare the CdS films with high transparency and low resistivity, they were deposited by varying Cd concentration with the constant S concentration in the solution using chemical bath deposition method. They were analyzed in terms of structural, optical and electrical properties of CdS films according to the $[S^{2-}]/[Cd^{2+}]$ ratio. In the case of Cd concentration higher than S concectration, CdS thin films were formed mainly by cluster- by-cluster formation due to the homogeneous reaction between Cd and S in the solution. Therefore the grain size increased and the transmittance decreased. On the other hand, in the case of Cd concentration lower than S concentration, CdS films were formed by heterogeneous reaction on the substrate rather than in the solution. The CdS films have the grains with the uniform circular shape of a few hundreds ${\AA}$. As the Cd concentration increased in the solution, the $[S^{2-}]/[Cd^{2+}]$ ratio decreased and the resistivity decreased by the increase in the carrier concentration due to the formation S vacancy by the excess Cd.

• Journal of Biomedical Engineering Research
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• v.24 no.3
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• pp.203-208
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• 2003

The effect of indium on the microstructure and hardness of a Au-Pt-Cu ternary alloy was investigated using optical microscopy, differential scanning calorimeter, scanning electron microscopy x-ray diffractometry, electron probe microanalizer and vickers hardness tester. A hardness of the solution floated Au-Pt-Cu-0.5In quarternary alloy with 0.5 wt.% was reached a maximum value (162 Hv) in 30 min at 550$^{\circ}C$ in the range of 150 to 950$^{\circ}C$ but that of the alloy was rapidly increased until 30 min with increasing aging time at 550$^{\circ}C$ and after that was remained almost constant value. Also, the microhardness of the matrix Au-Pt-Cu ternary alloy aged at 550$^{\circ}C$ for 30 min was continuously increased with indium contents and the grain size of Au-Pt-Cu ternary alloy decreased as increased indium contents. Analyses of EPMA and XRD revealed that the matrix Au-Pt-Cu-In quarternary alloy is composed of fcc structure and intermetallic InPt$_3$ precipitate with Ll$_2$ structure. Based on this investigation, it can be concluded that an increase in microhardness of Au-Pt-Cu-In quarternary alloy is due to precipitation hardening InPt$_3$ and grain size refinement.

• Korean Journal of Optics and Photonics
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• v.28 no.1
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• pp.9-15
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• 2017

We precisely measured and analyzed the dynamics of peptide-antibody interactions, using an ellipsometric biosensor based on a silicon substrate. To reduce the signal error due to the imperfect flatness of the substrate for extremely low concentrations of peptide, we fabricated the biosensor with a silicon substrate coated with Dextran SAM, instead of a glass prism coated with a thin metallic thin film. At an injection speed of $100{\mu}l/min$ of buffer liquid, we detected the dynamics of antibody-Dextran SAM or peptide-antibody fixed on biosensor, respectively. We detected the dynamics of antibody-Dextran SAM interactions down to a low concentration of 5 ng per liter, and we precisely measured the dynamics of association and dissociation of peptide and antibody down to 100 nM of peptide. We obtained the rate constants for association and dissociation from fitting the data by using deduced dynamical equation. As a result, we obtained an equilibrium constant for dissociation of 97 nM of peptide-antibody complex, which belongs to Class I.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.93-100
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• 2013

Many researches have been carried out to reduce and/or to capture the major global warming gases. Especially, the hydrate formation mechanisms were intensively investigated for carbon dioxide sequestration and storage process applications. In this study, the characteristics of film-type crystal growth mechanism of carbon dioxide hydrate were comprehensively examined. Carbon dioxide hydrate crystal was formed in semi-batch type stir reactor at various pressure conditions while the temperature was fixed to be constant to reduce and minimize the guest gas solubility effects. A supply gas composition was 99.999 % of Carbon dioxide, the observation data was collected by optical microscope adopted CCD camera (Nikon DS-5M/Fi1/2M-U2). This study revealed that the guest gas pressure changes significantly altered the crystal growth mechanism and film growth rate of carbon dioxide hydrate crystal. The critical pressure of the carbon dioxide hydrate of crystal growth mechanism change was found to be 2.0 MPa. The capillary force and gas concentration gradient also significantly changed the film-type crystal growth mechanism of carbon dioxide hydrate crystal.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.477-477
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• 2008

For more than three decades, the gate dielectrics in CMOS devices are $SiO_2$ because of its blocking properties of current in insulated gate FET channels. As the dimensions of feature size have been scaled down (width and the thickness is reduced down to 50 urn and 2 urn or less), gate leakage current is increased and reliability of $SiO_2$ is reduced. Many metal oxides such as $TiO_2$, $Ta_2O_4$, $SrTiO_3$, $Al_2O_3$, $HfO_2$ and $ZrO_2$ have been challenged for memory devices. These materials posses relatively high dielectric constant, but $HfO_2$ and $Al_2O_3$ did not provide sufficient advantages over $SiO_2$ or $Si_3N_4$ because of reaction with Si substrate. Recently, $HfO_2$ have been attracted attention because Hf forms the most stable oxide with the highest heat of formation. In addition, Hf can reduce the native oxide layer by creating $HfO_2$. However, new gate oxide candidates must satisfy a standard CMOS process. In order to fabricate high density memories with small feature size, the plasma etch process should be developed by well understanding and optimizing plasma behaviors. Therefore, it is necessary that the etch behavior of $HfO_2$ and plasma parameters are systematically investigated as functions of process parameters including gas mixing ratio, rf power, pressure and temperature to determine the mechanism of plasma induced damage. However, there is few studies on the the etch mechanism and the surface reactions in $BCl_3$ based plasma to etch $HfO_2$ thin films. In this work, the samples of $HfO_2$ were prepared on Si wafer with using atomic layer deposition. In our previous work, the maximum etch rate of $BCl_3$/Ar were obtained 20% $BCl_3$/ 80% Ar. Over 20% $BCl_3$ addition, the etch rate of $HfO_2$ decreased. The etching rate of $HfO_2$ and selectivity of $HfO_2$ to Si were investigated with using in inductively coupled plasma etching system (ICP) and $BCl_3/Cl_2$/Ar plasma. The change of volume densities of radical and atoms were monitored with using optical emission spectroscopy analysis (OES). The variations of components of etched surfaces for $HfO_2$ was investigated with using x-ray photo electron spectroscopy (XPS). In order to investigate the accumulation of etch by products during etch process, the exposed surface of $HfO_2$ in $BCl_3/Cl_2$/Ar plasma was compared with surface of as-doped $HfO_2$ and all the surfaces of samples were examined with field emission scanning electron microscopy and atomic force microscope (AFM).

• 전기의세계
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• v.28 no.4
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• pp.53-63
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• 1979

Interface recombination velocity in $Al_{x}$G $a_{1-x}$ As-GaAs and $Al_{0.85}$, G $a_{0.15}$ As-GaA $s_{1-y}$S $b_{y}$ heterojunction systems is studied as a function of lattice mismatch. The results are applied to the design of highly efficient III-V heterojunction solar cells. A horizontal liquid-phase epitaxial growth system was used to prepare p-p-p and p-p-n $Al_{x}$G $a_{1-x}$ As-GaA $s_{1-y}$S $b_{y}$-A $l_{x}$G $a_{1-x}$ As double heterojunction test samples with specified values of x and y. Samples were grown at each composition, with different GaAs and GaAs Sb layer thicknesses. A method was developed to obtain the lattice mismatch and lattice constants in mixed single crystals grown on (100) and (111)B oriented GaAs substrates. In the AlGaAs system, elastic lattice deformation with effective Poisson ratios .mu.$_{eff}$ (100=0.312 and .mu.$_{eff}$ (111B) =0.190 was observed. The lattice constant $a_{0}$ (A $l_{x}$G $a_{1-x}$ As)=5.6532+0.0084x.angs. was obtained at 300K which is in good Agreement with Vegard's law. In the GaAsSb system, although elastic lattice deformation was observed in (111) B-oriented crystals, misfit dislocations reduced the Poisson ratio to zero in (100)-oriented samples. When $a_{0}$ (GaSb)=6.0959 .angs. was assumed at 300K, both (100) and (111)B oriented GaAsSb layers deviated only slightly from Vegard's law. Both (100) and (111)B zero-mismatch $Al_{0.85}$ G $a_{0.15}$As-GaA $s_{1-y}$S $b_{y}$ layers were grown from melts with a weight ratio of $W_{sb}$ / $W_{Ga}$ =0.13 and a growth temperature of 840 to 820 .deg.C. The corresponding Sb compositions were y=0.015 and 0.024 on (100) and (111)B orientations, respectively. This occurs because of a fortuitous in the Sb distribution coefficient with orientation. Interface recombination velocity was estimated from the dependence of the effective minority carrier lifetime on double-heterojunction spacing, using either optical phase-shift or electroluminescence timedecay techniques. The recombination velocity at a (100) interface was reduced from (2 to 3)*10$^{4}$ for y=0 to (6 to 7)*10$^{3}$ cm/sec for lattice-matched $Al_{0.85}$G $a_{0.15}$As-GaA $s_{0.985}$S $b_{0.015}$ Although this reduction is slightly less than that expected from the exponential relationship between interface recombination velocity and lattice mismatch as found in the AlGaAs-GaAs system, solar cells constructed from such a combination of materials should have an excellent spectral response to photons with energies over the full range from 1.4 to 2.6 eV. Similar measurements on a (111) B oriented lattice-matched heterojunction produced some-what larger interface recombination velocities.ities.ities.s.

• Journal of the Korean Chemical Society
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• v.55 no.2
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• pp.208-217
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• 2011

The effects of pH and temperature on the removal of two dyes (neutral red; NR and malachite green oxalates; MG) from aqueous effluents using Maghnia montmorillonite clay in a batch adsorption process were investigated. The results showed the stability of the optical properties of MG in aqueous solution and adsorbed onto clay under wide range of pH 3-9. However, the interaction of NR dye with clay is accompanied by a red shift of the main absorption bands of monomer cations under pH range of 3-5, whereas, those of neutral form remains nearly constant over the pH range of 8-12. The optimal pH for favorable adsorption of the dyes, i.e. ${\geq}$90% has been achieved in aqueous solutions at 6 and 7 for NR and VM respectively. The most suitable adsorption temperatures were 298 and 318 K with maximum adsorption capacities of 465.13mg/g for NR and 459.89 mg/g for MG. The adsorption equilibrium results for both dyes follow Langmuir, Freundlich isotherms. The numerical values of the mean free energy $E_a$ of 4.472-5.559 kj/mol and 2.000-2.886 kj/mol for NR and MG respectively indicated physical adsorption. Various thermodynamic parameters, such as ${\Delta}H^{\circ}$, ${\Delta}S^{\circ}$, ${\Delta}G^{\circ}$ and Ea have been calculated. The data showed that the adsorption process is spontaneous and endothermic. The sticking probability model was further used to assess the potential feasibility of the clay mineral as an alternative adsorbent for organic ion pollutants in aqueous solution.

• Food Science and Preservation
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• v.22 no.5
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• pp.636-643
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• 2015

This study investigated changes in quality and sensory characteristics of soy sauce (Kanjang) with added Astragalus membranaceus (AK) to develop a new soy sauce product with improved sensory characteristics. The pure salinity slowly increased, but AK 10% decreased. The pH was a constant in all samples. The soluble solid content (Brix) increased after 2 months, but AK 10% decreased. With increased addition of Astragalus membranaceus (AM), the optical density increased after 4 months. The amino nitrogen increased in soy sauce with AK 5%. The total free amino acid content gradually increased in soy sauce with AK 5% aged for 6 months. As the addition of AM increased, the crude protein level decreased, but there was no difference between AK 0% and 5%. The sensory tests of AK 5% after 6 months showed higher acceptance. According to the aging period, the acceptability of AK 5% was the best. The results showed that soy sauce with of AK 5% and aged for 6 months exhibits greatly enhanced quality and sensory characteristics. Therefore, it is expected to be used as a natural resources in seasoning area.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.374-379
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• 1998

$Mn_1-xCr_xPt_3$ alloy films have been prepared by depositing (Mn, Cr)/Pt multilayers using a rf magnetron sputterer followed by heat treatment. Small and wide angle x-ray diffractometry, magnetic hysteresis loops and Kerr rotation angle spectra of the films have been measured and used to investigate structural, magnetic and magneto-optic properties of the films. The films had a crystal structure of ordered AuCu$_3$ type and the strong preferred orientation of a (111)plane parallel to the film surface. The saturation magnetization of the films was decreased with Cr content reaching almost zero near x=0.58 and then increased for further increasement of Cr content up to x=0.77 over that stayed almost constant. This indicated that Cr atoms were antiferromagnetically coupled with Mn atoms. The magnetic easy axis of MnPt$_3$(x=0) film was parallel to the film surface but those of the films with x$\geq$0.58 increased as Cr content increased reaching about 4 kOe at x=1(CrPt$_3$). The dependence of the Kerr rotation angle on the Cr content was similar to that of the saturation magnetization on the Cr content. The films with x=0.77 and x=1 showed the larger Kerr rotation angle at the wavelengths of near infrared compared to the magneto-optic recording medium, TbFeCo, currently being used.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.2
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• pp.122-127
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• 2021

This paper produces CdS thin film using ITO glass as substrates. The MDS (Multiplex Deposition Sputter System) was used to produce devices by changing RF power and deposition time. The manufactured specimen was analyzed for its optical properties. The purpose of this paper is to find the fabrication conditions that can be applied to the photo-absorbing layer of solar cells. When RF power was 50W and deposition time was 10 minutes, the thickness was measured at 64Å. At 100W, the thickness was measured at 406Å and at 150 W, the thickness was measured at 889Å. Thin films were found to increase in thickness as RF power increased. As a result of the light transmittance measurement, 550-850nm was observed to have a transmittance of approximately 70% or more when the RF power was 50W, 100W, and 150W. Increasing RF power increased thickness and increased particle size, resulting in increased thin film density, resulting in reduced light transmittance. When RF power was 100W and deposition time was 15 minutes, the band gap was calculated at 3.998eV. When deposition time is 20 minutes, it is 3.987eV, 150W is 3.965eV at 15 minutes, and 3.831eV at 20 minutes. It was measured that the band gap decreased as the RF power increased. At XRD analysis, diffraction peaks at 2Θ=26.44 could be observed regardless of changes in RF power and deposition time. The FWHM was shown to decrease with increasing deposition time. And it was measured that the particle size increased as RF power was constant and deposition time was increased.