• Korean Journal of Materials Research
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• v.13 no.6
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• pp.347-351
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• 2003

II-Ⅵ ZnO compound semiconductor thin films were grown on $\alpha$-Al$_2$O$_3$(0001) single crystal substrate by radical beam assisted molecular beam epitaxy and the optical properties were investigated. Zn(6N) was evaporated using Knudsen cell and O radical was assisted at the partial pressure of 1$\times$10$^{4}$ Torr and radical beam source of 250-450 W RF power. In $\theta$-2$\theta$ x-ray diffraction analysis, ZnO thin film with 500 nm thickness showed only ZnO(0002)and ZnO(0004) peaks is believed to be well grown along c-axis orientation. Photoluminescence (PL) measurement using He-Cd ($\lambda$=325 nm) laser is obtained in the temperature range of 9 K-300 K. At 9 K and 300 K, only near band edge (NBE) is observed and the FWHM's of PL peak of the ZnO deposited at 450 RF power are 45 meV and 145 meV respectively. From no observation of any weak deep level peak even at room temperature PL, the ZnO grains are regarded to contain very low defect density and impurity to cause the deep-level defects. The peak position of free exciton showed slightly red-shift as temperature was increased, and from this result the binding energy of free exciton can be experimentally determined as much as $58\pm$0.5 meV, which is very closed to that of ZnO bulk. By van der Pauw 4-point probe measurement, the grown ZnO is proved to be n-type with the electron concentration($n_{e}$ ) $1.69$\times$10^{18}$$cm^3$, mobility($\mu$) $-12.3\textrm{cm}^2$/Vㆍs, and resistivity($\rho$) 0.30 $\Omega$$\cdot$cm.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.977-981
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• 1998

Controlling the wafer temperatures from 200 to$500^{\circ}C$, low resistive tungsten thin films used for VLSI metallization are deposited by PECVD method. Resistivities of plasma deposited tungsten thin films are very sensitive to the $H_2/WF_6 $ partial pressure ratios. Residual stress behaviors of the films as a function of plasma power density were also studied. At the power density under the $0.7W/\textrm{cm}^2$, residual stress of W film is about $2.4\times10^9dyne/\textrm{cm}^2$. When the power density is. however, increased from 1.8 to $2.7W/\textrm{cm}^2$, residual stress is suddenly increased from $8.1\times10^9$ to $1.24\times10^{10}dyne/\textrm{cm}^2$ ue to the ion or radical bombardment at high power density.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.405-412
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• 2006

In order to realize a stably propagating flame in a narrow channel, flame instabilities resulting from flame-wall interaction should be avoided. In particular flame quenching is a significant issue in micro combustion devices; quenching is caused either by excessive heat loss or by active radical adsorptions at the wall. In this paper, the relative significance of thermal and chemical effects on flame quenching is examined by means of quenching distance measurement. Emphasis is placed on the effects of surface defect density on flame quenching. To investigate chemical quenching phenomenon, thermally grown silicon oxide plates with well-defined defect distribution were prepared. ion implantation technique was used to control defect density, i.e. the number of oxygen vacancies. It has been found that when the surface temperature is under $300^{\circ}C$, the quenching distance is decreased on account of reduced heat loss; as the surface temperature is increased over $300^{\circ}C$, however, quenching distance is increased despite reduced heat loss effect. Such abberant behavior is caused by heterogeneous surface reactions between active radicals and surface defects. The higher defect density, the larger quenching distance. This result means that chemical quenching is governed by radical adsorption that can be parameterized by oxygen vacancy density on the surface.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2008.05a
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• pp.23-29
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• 2008

- High Density Plasma Source-CCP-Dual/Triple, RF Frequency Control - Radical/Flux Analysis - Low Pressure Process - Chamber Design (Process gap/Wall gap) - Chamber Temp. Control. - ESC Dielectric Materials - Uniform Gas Injection

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.316-319
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• 2000

In the case of immobilizing of glucose oxidase into polypyrrole (PPy) using electrosynthesis, the glucose oxidase (GOx) forms a coordinate bond with the polymer's backbone. However, because of intrinsic insulation and net-chain of the enzyme, the charge transfer and mass transport are obstructed during the film growth. Therefore, the film growth is dull. We synthesized the enzyme electrode by electropolymerization added some organic solvent, A formative seeds of film growth is delayed by adding the solvent. The delay is induced by radical transfer between the solvent and pyrrole monomer. In the case of adding ethanol, the radical transfer shares the contribution of dopant between electrolyte anion and GOx polyanion. This may lead to increase amount of immobilized the enzyme in ppy. However, adding tetrahydrofuran (THF), the radical transfer is more brisk, resulting in short chained polymer. Therefore, the doping level is lowered and then amount of immobilized of enzyme is decreased. For the UV absorption spectra of synthetic solution before synthesis and after, in the case of ethanol added, the optical density was slightly decreased for the GOx peaks. It suggests amount of GOx in the solution was decreased and amount of GOx in the film was increased. We established qualitatively that amount of immobilization can be improved by adding a little ethanol in the synthetic solution. It is due to radical transfer reaction. The radical transfer shares the contribution of dopant between small and fast electrolyte anion and big and slow GOx polyanion.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.26-32
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• 2014

In this study, DC (Direct current) type steam plasma igniter is developed for effective ignition of high-energy density metal aluminum and gas temperature is measured by emission spectrum of OH radical. Because of the ultra-high gas temperature, the DC plasma jet is measured by Boltzmann plot method which is the non-contact optical technique and spectrum comparison-analysis. And both methods were applied to experiment after accurate verification. As a result, we could identify that plasma jet temperature is 2900 K ~ 5800 K in the 30 mm range from the nozzle tip.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.40-44
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• 2000

In this paper, since the research on the etching of SrBi$_2$Ta$_2$O$_{9}$ (SBT) thin film was few (specially Cl$_2$-base ), we had studied the surface reaction of SBT thin films using the OES in high density plasma etching as a function of rf power, dc bias voltage, and Cl$_2$/(C1$_2$+Ar) gas mixing ratio. It had been found that the etch rate of SBT thin films appeared to be more affected by the physical sputtering between Ar ions and surface of the SBT compared to the chemical reaction in our previous papers$^{1.2}$ . The change of Cl radical density that is measured by the OES as a function of gas combination showed the change of the etch rate of SBT thin films. Therefore, the chemical reactions between Cl radical in plasma and components of the SBT enhance to increase the etch rates of SBT thin films and these results were confirmed by XPS analysis.

• Journal of the East Asian Society of Dietary Life
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• v.23 no.5
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• pp.597-604
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• 2013

This study was conducted to investigate the effect of mulberry leaf powder on the antioxidant activity and the quality characteristics of maejakgwa (a Korean traditional cookie). Maejakgwa was prepared with different amounts of mulberry leaf powder (in ratios of 0, 3, 6, 9 and 12% to the flour quantity). The antioxidant activity was estimated by DPPH free radical scavenging activity and the total phenol content in mulberry leaf powder and maejakgwa. For analyzing the quality characteristics, bulk density and the pH of the dough, moisture contents, color, texture profile analysis and sensory evaluations were measured. The total phenol contents, DPPH free radical scavenging activity, bulk density of the batter and the a values of maejakgwa significantly increased with increasing mulberry leaf powder, whereas the pH of the batter, L values and b values of the maejakgwa significantly decreased with increasing mulberry leaf powder content. Finally, the results of the acceptance test indicated that maejakgwa containing 6% mulberry leaf powder had the highest scores. From these results, we suggest that mulberry leaf is a good ingredient for increasing consumer acceptability as well as the functionality of maejakgwa.

• Biomedical Science Letters
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• v.12 no.4
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• pp.355-359
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• 2006

This investigation was performed to study the antioxidant activities of Cornus officinalis Sieb extracts and the effect of Cornus officinalis Sieb extracts on glucose, lipid metabolism in diabetic rats. DPPH free radical scavanging activity and superoxide anion radical scavenging of Cornus officinalis Sieb extracts were 94.7% and 92.1%, respectively. Streptozotocin (45 mg/kg body weight, i.p.) induced diabetic rats showed a significant increases of plasma glucose, triglyceride and total cholesterol, concomitantly significant decrease of plasma high density lipoprotein. Glutathione level were decrease in cytosol of liver, lung and brain tissue of rats. Lipid peroxide were increase in microsome of liver cells. Group 1 and 2 were treated with Cornus officinalis Sieb extracts 200 mg/kg body weight and 100 mg/kg body weight for 24 days, individually. Group 1 and 2 rats showed decreased plasma glucose, triglyceride, total cholesterol and lipid peroxide in microsome of liver, and increased plasma high density lipoprotein and glutathione in cytosol of liver, lung and brain. The result suggest that Cornus officinalis Sieb extracts may normalize the Impaired antioxiants status in streptozotocin induced diabetic rats. Cornus officinalis Sieb extracts were used to improve the imbalance between free radicals and antioxidant system due to the diabetes.

• The Korean Journal of Food And Nutrition
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• v.26 no.4
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• pp.646-654
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• 2013

This study was conducted to investigate the effect of pine needle powder on antioxidant activity and the quality characteristics of Majakgwa (Korean traditional cookie). Majakgwa was prepared with different amounts of pine needle powder (in ratios of 0, 3, 6, 9 and 12% to the flour quantity). The antioxidant activity was estimated by DPPH free radical scavenging activity and by the total phenol content in pine needle powder and Majakgwa. For analyzing the quality characteristics, bulk density and pH of the dough, moisture content, volume, color, texture profile analysis and sensory evaluations were measured. The bulk density, volume, total phenol contents and DPPH free radical scavenging activity of Majakgwa significantly increased with increasing pine needle powder (p<0.001), whereas the pH of the dough, L values and b values of the Majakgwa significantly decreased with increasing pine needle powder content (p<0.001). The consumer acceptability score for the 6% pine needle Majakgwa ranked significantly higher (p<0.001) than those of the other groups in overall preference, flavor, taste, crispiness and color. Acid value and peroxide value was lower in Majakgwa with pine needle powder than control. From these results;we suggest that pine needle powder is a good ingredient for increasing consumer acceptability and functionality of Majakgwa.