• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.413-416
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• 2004

In this study, zinc oxide(ZnO) having large misfit(18.2%) with sapphire was tried to be grown on very thin nitride buffer layers. For the creation of various kinds of nitride buffer layer, sapphire surface was modified by an irradiation of nitrogen ion beam with low energy generated from stationary plasma thruster(SPT) at room temperature. After the irradiation of ion beam, Al-N and Al-O-N bonding was identified to be formed as nitride buffet layers. Surface morphology was measured by AFM and then ZnO growth was followed by pulsed laser deposition(PLD). Their properties are analyzed by XRD, AFM, TEM, and PL. We observed that surface morphology was improved and deep level emission related to defects was almost vanished in PL spectra from the ZnO grown on nitride buffer layer.

• 한국진공학회지
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• 제14권4호
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• pp.201-206
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• 2005

본 연구에서는 HVPE (Hydride Vapor Phase Epitaxy) 방법으로 Si 위에 GaN/AIN/Al/Si 구조를 제작하고, AlN 버퍼층의 두께에 따른 광학적 특성을 조사함으로써 효과적인 eaN 성장을 위한HVPE에서의 공정 방법을 개선하고자 하였다. 이를 위해 Al을 증착한 Si 기판과 그렇지 않은 경우를 PL측정을 통해 그 효과를 관찰하였고, $5{\AA}$ 두께의 Al 대해 AlN 버퍼층의 두께를 변화시켜가면서 GaN를 성장시켜 그 특성을 조사하였다. Al을 증착한 경우가 증착하지 않은 경우에 비해 광학적 특성이 우수한 것으로 나타났으며, AlN의 두께 변화에 대해서는 양질의 GaN를 얻기 위한 최적의 두께는 약 $260{\AA}$ 인 것으로 나타났다. 이 경우 SEM을 이용한 표면사진에서 GaN의 초기성장이 hexagonal형태로 성장되고 있음을 관찰할 수 있었다. 또한 XRD의 회절 패턴은 GaN가 {0001} 방향으로 우선 배향성을 가지고 성장되고 있음을 보여주고 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.50-53
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• 1994

In this study. we report the properties of optically pumped stimulated emission at room temperature (RT) from column-III nitride semiconductors of GaN, GaInN, AlGaN/GaN double hetero-structure (DH) and AlGaN/GaInN DH which grown by low pressure metal-organic vapor phase epitaxy on sapphire substrate using an AIN buffer-layer. The peak wavelength of the stimulated emission at RT from AlGaN/GaN DH is 370nm and the threshold of excitation pumping power density (P$\_$th/) is about 89㎾/$\textrm{cm}^2$, and they from AlGaN/GaInN DH are 403nm and 130㎾/$\textrm{cm}^2$, respectively. The P$\_$th/ of AlGaN/GaN and AlGaN/GaInN DHs are lower than the bulk materials due to optical confinement within the active layers of GaN and GaInN. The optical gain and the polarization of stimulated emission characteristics are presented in this article.

• Journal of Nutrition and Health
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• 제36권4호
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• pp.335-343
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• 2003

This study was designed to investigate the hypoglycemic effects of Benincasa hispida (Wax gourd) in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in the male rats by intravenous injection of STZ at a dose of 45 mg/kg dissolved in citrate buffer. The diabetic animals then had plasma glucose concentration of above 300mg/dl. The experimental groups were divided into five groups; normal, STZ-control and three Wax gourd groups (5%, 10% and 20% intake groups). Normal and STZ-control groups were fed on a AIN-93 diet and experimental groups were fed a AIN-93 diet with the Wax gourd powder (5%, 10% and 20%/kg diet) for 4 weeks. The body weight, diet intake and feed efficiency ratio (FER) were monitored. The blood glucose and cholesterol levels were determined everyweek. After 4 weeks, the rats were sacrificed and the levels of glucose, insulin, cholesterol, HDL-cholesterol, triglyceride and free fatty acids in plasma and levels of glycogen in liver and muscle were analyzed. Diabetic rats showed the lower weight gain compared to the normal rats. The weight gain and feed efficiency ratios in 15 and 20% Wax gourd groups were higher than in STZ-control group. The plasma glucose levels were significantly lower in all Wax gourd groups than in STZ-control group. The plasma insulin levels in diabetic groups were not significantly different compared to the normal group, but the level of 20% Wax gourd group was higher than other diabetic groups. The experimental diabetic groups showed the higher levels of muscle glycogen compared to STZ-control group. The lower levels of plasma cholesterol were noticed in 20% Wax gourd group throughout the experimental period. The plasma level of triglyceride was elevated in STZ-diabetic control and the levels were slightly decreased in Wax gourd groups. Rats of 10% Wax gourd group showed the lower levels of plasma free fatty acids. It is suggested, from the results, that the possibility of therapeutic or preventive use of wax gourd to the diabetes mellitus.

• 한국진공학회지
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• 제11권1호
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• pp.50-58
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• 2002

Si 기판 위에 GaN의 성장은 Si이 사파이어보다 값이 저렴하고, 기존의 Si의 직접회로 공정에 GaN를 쉽게 접목시킬 수 있는 측면에서 다양한 장점이 있다. 그러나, Si은 GaN와의 격자상수와 열팽창계수의 차이가 사파이어보다 크며, 이로 인해 격자부정합에 의한 여러 결함을 발생시킨다. 따라서, Si 기판 위에 고품질의 GaN를 얻기 위해서는 AlN과 같은 완충층을 사용하여 격자부정합에 의한 결함을 줄여야 한다. 본 연구에서는 Si (111) 기판 위에 MOCVD, 스퍼터링과 MOMBE의 3가지 방법으로 결정성이 다른 3가지 유형의 AlN 완충층을 얻은 후, MOCVD법으로 GaN를 증착시켜 각각의 성장특성을 비교하였다. AlN 완충층과 GaN의 격자결합, 완충층의 표면 거칠기가 격자결함에 미치는 영향, 결정성, 성장방향, 결함(공공, 적층결함, 전위) 등을 TEM, XRD를 이용해 비교 분석하였다. AlN완충층의 결정성은 GaN의 성장에 있어 매우 큰 영향을 미치는 것을 확인할 수 있었다. 초기 성장과정에서 MOCVD과 MOMBE 법으로 성장시킨 AlN 완충층은 GaN 초기 성장에서 out-of-plane의 성장방향이 틀어지는 것을 감소시켜 주었다.

• E2M - 전기 전자와 첨단 소재
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• 제8권3호
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• pp.272-277
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• 1995

We report the properties of optically pumped stimulated emission at room temperature (RT) from column-III nitride semiconductors of GaN, AlGaN/GaN double heterostructure (DH) and AlGaN/GaInN DH which prepared on a sapphire substrate using an AIN buffer-layer by the nietalorganic vapor phase epitaxy (MOVPE) method. The peak wavelength of the stimulated emission at RT from AIGaN/GaN DH is 369nm and the threshold of excitation pumping power density (P$\_$th/) is about 84kW/cm$\^$2/, and they from AlGaN/GaInN DH are 402nm and 130kW/cm$\^$2/ at the pumping power density of 200kW/cm$\^$2/, respectively. The P$\_$th/ of AIGaN/GaN and AlGaN/GaInN DHs are lower than the single layers of GaN and GaInN due to optical confinement within the active layers of GaN and GaInN, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.13-16
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• 2009

In this study, AlN thin films were deposited on a polycrystalline (poly) 3C-SiC buffer layer for surface acoustic wave (SAW) applications using a pulsed reactive magnetron sputtering system. AFM, XRD and FT-IR were used to analyze structural properties and preferred orientation of the AlN/3C-SiC thin film. Suitability of the film in SAW applications was investigated by comparing the SAW characteristics of an interdigital transducer (IDT)/AlN/3C-SiC structure with the IDT/AIN/Si structure at 160 MHz in the temperature range $30-150^{\circ}C$. These experimental results showed that AlN films on the poly 3C-SiC layer were highly (002) oriented. Furthermore, the film showed improved temperature stability for the SAW device, $TCF\;=\;-18\;ppm//^{\circ}C$. The change in resonance frequency according to temperature was nearly linear. The insertion loss decrease was about $0.033dB/^{\circ}C$. However, some defects existed in the film, which caused a slight reduction in SAW velocity.

• Journal of Nutrition and Health
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• 제33권2호
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• pp.115-123
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• 2000

This study evaluates the effect of Dioscorea japonica Thunb subfractions on hyperglycemia and the composition of energy metabolites in diabetic rats. Diabetes emllitus was induced in male Sprague-Dawley rats by an injection of streptozotocin(STZ) dissolved in a citrate buffer into the tail vein at a dose of 45㎎/㎏ of body weight. Diabetic rats were assigned to 6 groups; STZ-control, subfraction A, B , C, D and E groups. All groups were fed an AIN-76 diet. The second butanol fraction of Dioscorea administered orally with carboxymethyl cellucose for 10 days after the STZ injection Body weight gain, diet intake and organ weights were monitored Levels of hematocrit, blood glucose, liver and muscle glycogen were measured. Levels of cholesterol, triglycerides and free fatty acids were also assayed. Body weight losses were observed by subfraction A group. Liver and kidney weights were not affected in any of the subgractioned groups. The decrease of blood glucose in daibetic rats which were fed Dioscorea japonica Thunb was significantly greater than the dicrease of blood glucose in the STZ-control group. cholesterol plasma level was not influenced in any subfraction of Dioscorea japonica Thunb. Liver triglyceride levels were significantly lowered in subfraction A compared with the STZ-control group. This study's results suggest that oral administration of subfraction C of Dioscorea japonica Thunb frction is capabl of reducing blood glucose, plasma triglyceride and free fatty acid levels, and therefore Dioscorea japonica Thunb may contain antihyperglycemic compounds.

• 한국재료학회지
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• 제12권5호
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• pp.387-390
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• 2002

A new approach of using double buffer layers of AlN and GaN for growth of GaN films on Si has been undertaken via molecular beam epitaxy using ammonia. The first buffers layer of AlN was grown using $N_2$plasma and the second of GaN was grown using ammonia. The surface roughness of the grown films was investigated by atomic force microscope and was compared with the normally grown films on sapphire. Double crystal x-ray rocking curve and low temperature photoluminescence techniques were employed for structural and optical properties examination. Donor bound exciton peak at 3.481 eV with full width half maximum of 41 meV was observed at 13K.

• Journal of Nutrition and Health
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• 제41권7호
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• pp.583-593
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• 2008

This study was designed to examine the effects of Salicornia herbacea L. (glasswort: GW) on hepatic antioxidative enzyme activities in diabetic rats. Diabetes mellitus was induced in male Sprague-Dawley rats weighing 200-220g by an injection of streptozotocin (STZ) dissolved in a citrate buffer into the tail vein at a dose of 45 mg/kg of body weight. Sprague-Dawley rats were fed an AIN-93 recommended diet and the experimental groups were fed a modified diet containing 10% and 20% of glasswort powder for 4 weeks. The experimental groups were divided into 6 groups which consisted of normal (N)-control group, N-GW 10% and N-GW 20% treated groups, STZ-control, STZ-GW 10% and STZ-GW 20% treated groups. The activities of Xanthine oxidase (XOD), glutathione- S-transferase (GST), glutathione peroxidase (GPX), glutathione reductase (GR), superoxide dismutase (SOD) and CAT (CAT) were measured in the homogenates of liver. The activity of CAT was lower in the supplementary group with glasswort compare to the STZcontrol group but it was not significantly different. The activity of SOD was not significant in all of experimental groups. The activity of GR was significantly increased in the normal supplementary group with glasswort, and GPX activity was significantly increased in STZ-GW 10% group compare to the STZ-control group. The activity of XOD was significantly decreased in the all of supplementary groups with glasswort. The activity of GST was significantly increased in the N-GW 20% group and it was significantly decreased in the STZ-GW 20% group. These results show that the supplementation of glasswort may have favorable influence on antioxidative status in diabetic rats and it may be useful for the diabetic complications as functional food.