• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.413-416
• /
• 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.

• Journal of the Korean Vacuum Society
• /
• v.14 no.4
• /
• pp.201-206
• /
• 2005

In this work, we tried to improve the fabrication process in HVPE (Hydride Vapor Phase Epitaxy) system by using Si(111) substrate with pre-deposited Al layer. PL measurements was done for samples with and without pre-deposited Al on Si and it was also examined the dependence of the optical characteristic properties on AlN buffer thickness for GaN/AIN/Al/Si. A sample with thin Al nucleation layer on Si substrate reveals a better optical property than the other. And it suggests that the thickness for AlN buffer layer with thin Al nucleation layer on Si(111) substrate is most proper about $260{\AA}$ to grow GaN in HVPE system. The surface morphology of GaN clearly shows the hexagonal crystallization. The XRD pattern showed strong peak at GaN{0001} direction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1994.11a
• /
• pp.50-53
• /
• 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
• /
• v.36 no.4
• /
• pp.335-343
• /
• 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.

• Journal of the Korean Vacuum Society
• /
• v.11 no.1
• /
• pp.50-58
• /
• 2002

The growth of GaN films on Si substrate has many advantages in that Si is less expensive than sapphire substrate and that integration of GaN-based devices with Si substrate is easier The difference of lattice constant and thermal expansion coefficient between GaN and Si is larger than those between GaN and sapphire. However, which results in many defects into the grown GaN. In order to obtain high duality GaN films on Si substrate, we need to reduce defects using the buffer layer such as AlN. In this study, we prepared three types of AlN buffer layer with various crystallinity on Si (111) substrate using MOCVD, Sputtering and MOMBE methods. GaN was grown by MOCVD on three types of AlN/Si substrate. Using TEM and XRD, we carried out comparative investigation of growth and properties of GaN deposited on the various AlN buffers by characterizing lattice coherency, crystallinity, growth orientation and defects formed (voids, stacking faults, dislocations, etc). It is found that the crystallinity of AlN buffer layer has strong effects on growth of GaN. The AlN buffer layers grown by MOCVD and MOMBE showed the reduction of out-of-plane misorientation of GaN at the initial growth stage.

• Electrical & Electronic Materials
• /
• v.8 no.3
• /
• pp.272-277
• /
• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.04b
• /
• pp.13-16
• /
• 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
• /
• v.33 no.2
• /
• pp.115-123
• /
• 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.

• Korean Journal of Materials Research
• /
• v.12 no.5
• /
• pp.387-390
• /
• 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
• /
• v.41 no.7
• /
• pp.583-593
• /
• 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.