• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.107-107
• /
• 2000

최근 반도체 소자의 고집적화 및 대용량화의 경향에 다라 MOSFET 소자 제작에 이동되는 게이트 산화막의 두께가 수 nm 정도까지 점점 얇아지는 추세이고 Giga-DRAM급 차세대 UNSI소자를 제작하기 위해 5nm이하의 게이트 절연막이 요구된다. 이런 절연막의 두께감소는 게이트 정전용량을 증가시켜 트랜지스터의 속도를 빠르게 하며, 동시에 저전압동작을 가능하게 하기 때문에 게이트 산화막의 두께는 MOS공정세대가 진행되어감에 따라 계속 감소할 것이다. 따라서 절연막 두께는 소자의 동작 특성을 결정하는 중요한 요소이므로 이에 대한 정확한 평가 방법의 확보는 공정 control 측면에서 필수적이다. 그러나, 절연막의 두께가 작아지면서 게이트 산화막과 crystalline siliconrksm이 계면효과가 박막의 두께에 심각한 영향을 주기 때문에 정확한 두께 계측이 어렵고 계측방법에 따라서 두께 계측의 차이가 난다. 따라서 차세대 반도체 소자의 개발 및 양산 체계를 확립하기 위해서는 산화막의 두께가 10nm보다 작은 1nm-5nm 수준의 박막 시료에 대한 두께 계측 방법이 확립이 되어야 한다. 따라서, 본 연구에서는 습식 산화 공정으로 제작된 3nm-7nm 의 게이트 절연막을 현재까지 알려진 다양한 두께 평가방법을 비교 연구하였다. 절연막을 MEIS (Medim Energy Ion Scattering), 0.015nm의 고감도를 가지는 SE (Spectroscopic Ellipsometry), XPS, 고분해능 전자현미경 (TEM)을 이용하여 측정 비교하였다. 또한 polysilicon gate를 가지는 MOS capacitor를 제작하여 소자의 Capacitance-Voltage 및 Current-Voltage를 측정하여 절연막 두께를 계산하여 가장 좋은 두께 계측 방법을 찾고자 한다.다. 마이크로스트립 링 공진기는 링의 원주길이가 전자기파 파장길이의 정수배가 되면 공진이 일어나는 구조이다. Fused quartz를 기판으로 하여 증착압력을 변수로 하여 TiO2 박막을 증착하였다. 그리고 그 위에 은 (silver)을 사용하여 링 패턴을 형성하였다. 이와 같이 공진기를 제작하여 network analyzer (HP 8510C)로 마이크로파 대역에서의 공진특서을 측정하였다. 공진특성으로부터 전체 품질계수와 유효유전율, 그리고 TiO2 박막의 품질계수를 얻어내었다. 측정결과 rutile에서 anatase로 박막의 상이 변할수록 유전율은 감소하고 유전손실은 증가하는 결과를 나타내었다.의 성장률이 둔화됨을 볼 수 있다. 또한 Silane 가스량이 적어지는 영역에서는 가스량의 감소에 의해 성장속도가 둔화됨을 볼 수 있다. 또한 Silane 가스량이 적어지는 영역에서는 가스량의 감소에 의해 성장속도가 줄어들어 성장률이 Silane가스량에 의해 지배됨을 볼 수 있다. UV-VIS spectrophotometer에 의한 비정질 SiC 박막의 투과도와 파장과의 관계에 있어 유리를 기판으로 사용했으므로 유리의투과도를 감안했으며, 유리에 대한 상대적인 비율 관계로 투과도를 나타냈었다. 또한 비저질 SiC 박막의 흡수계수는 Ellipsometry에 의해 측정된 Δ과 Ψ값을 이용하여 시뮬레이션한 결과로 비정질 SiC 박막의 두께를 이용하여 구하였다. 또한 Tauc Plot을 통해 박막의 optical band gap을 2.6~3.7eV로 조절할 수 있었다. 20$0^{\circ}C$이상으로 증가시켜도 광투과율은 큰 변화를 나타내지 않았다.부터 전분-지질복합제의 형성 촉진이 시사되었다.이것으로 인하여 호화억제에 의한 노화 방지효과가 기대되었지만 실제로 빵의 노화는 현저히 진행되었다

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.155.2-155.2
• /
• 2013

Strain-relaxed SiGe layer on Si substrate has numerous potential applications for electronic and opto- electronic devices. SiGe layer must have a high degree of strain relaxation and a low dislocation density. Conventionally, strain-relaxed SiGe on Si has been manufactured using compositionally graded buffers, in which very thick SiGe buffers of several micrometers are grown on a Si substrate with Ge composition increasing from the Si substrate to the surface. In this study, a new plasma process, i.e., the combination of PIII&D and HiPIMS, was adopted to implant Ge ions into Si wafer for direct formation of SiGe layer on Si substrate. Due to the high peak power density applied the Ge sputtering target during HiPIMS operation, a large fraction of sputtered Ge atoms is ionized. If the negative high voltage pulse applied to the sample stage in PIII&D system is synchronized with the pulsed Ge plasma, the ion implantation of Ge ions can be successfully accomplished. The PIII&D system for Ge ion implantation on Si (100) substrate was equipped with 3'-magnetron sputtering guns with Ge and Si target, which were operated with a HiPIMS pulsed-DC power supply. The sample stage with Si substrate was pulse-biased using a separate hard-tube pulser. During the implantation operation, HiPIMS pulse and substrate's negative bias pulse were synchronized at the same frequency of 50 Hz. The pulse voltage applied to the Ge sputtering target was -1200 V and the pulse width was 80 usec. While operating the Ge sputtering gun in HiPIMS mode, a pulse bias of -50 kV was applied to the Si substrate. The pulse width was 50 usec with a 30 usec delay time with respect to the HiPIMS pulse. Ge ion implantation process was performed for 30 min. to achieve approximately 20 % of Ge concentration in Si substrate. Right after Ge ion implantation, ~50 nm thick Si capping layer was deposited to prevent oxidation during subsequent RTA process at $1000^{\circ}C$ in N2 environment. The Ge-implanted Si samples were analyzed using Auger electron spectroscopy, High-resolution X-ray diffractometer, Raman spectroscopy, and Transmission electron microscopy to investigate the depth distribution, the degree of strain relaxation, and the crystalline structure, respectively. The analysis results showed that a strain-relaxed SiGe layer of ~100 nm thickness could be effectively formed on Si substrate by direct Ge ion implantation using the newly-developed PIII&D process for non-gaseous elements.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.249-249
• /
• 2013

Surface-enhanced Raman spectroscopy (SERS) is a sensitive approach to detect and to identify a variety of molecules. To enhance the Raman signal, optimization of the gap between nanostructures is quite important. One-dimensional materials such as nanowires, nanotubes, and nanograsses have great potential to be used in SERS due to their unique sizes and shape dependent characteristics. In this study we investigate a simple way to fabricate SERS substrates based on randomly grown copper oxide (CuO) nanowires. CuO nanograss is fabricated on pre-cleaned Cu foils. Cu oxidized in an ammonium ambient solution of 2.5 M NaOH and 0.1 M $(NH_4)_2S_2O_8$ at $4^{\circ}C$ for 10, 30, and 60 minutes. Then, Cu(OH)2 nanostructures are formed and dried at $180^{\circ}C$ for 2 h. With the drying process, the Cu(OH)2 nanostructure is transformed to CuO nanograss by dehydration reaction. CuO nanograss are grown randomly on Cu foil with the average length of 10 ${\mu}m$ and the average diameter of a 100 nm. CuO nanograsses are covered by Ag with various thicknesses from 10 to 30 nm using a thermal evaporator. Then, we immerse uncoated and Ag coated CuO nanowire samples of various oxidation times in a 0.001M methanol-based 4-mercaptopyridine (4-Mpy) in order to evaluate SERS enhancement. Raman shift and SERS enhancement are measured using a Raman spectrometer (Horiba, LabRAM ARAMIS Spectrometer) with the laser wavelength of 532 nm. Raman scattering is believed to be enhanced by the interaction between CuO nanograss and Ag island film. The gaps between Ag covered CuO nanograsses are diverse from <10 nm at the bottom to ~200 nm at the top of nanograsses. SERS signal are improved where the gaps are minimized to near 10s of nanometers. There are many spots that provide sufficiently narrow gap between the structures on randomly grown CuO nanograss surface. Then we may find optimal enhancement of Raman signal using the mapping data of average results. Fabrication of CuO nanograss based on a solution method is relatively simple and fast so this result can potentially provide a path toward cost effective fabrication of SERS substrate for sensing applications.

• Korean Journal of Medicinal Crop Science
• /
• v.21 no.5
• /
• pp.361-371
• /
• 2013

This study was performed to determine the antimelanogenic effect and tyrosinase inhibitory activities of anthocyanin rich fraction (AN-SLP) from Liriope platyphylla Wang et Tang seeds. Anthocyanins isolated from L. platyphylla seeds revealed the presence of four major anthocyanin components, which were tentatively identified as delphinidin-3-Oglucoside, delphinidin-3-O-rutinoside, petunidin-3-O-rutinoside, and malvidin-3-O-rutinoside using semipreparative HPLC, $^1H$-NMR, $^{13}C$ NMR, FAB-MS and LC/ES-MS. The inhibitory effect of AN-SLP on tyrosinase activity was studied using in vitro (against mushroom tyrosinase) and ex vivo (against B16 melanoma cell tyrosinase) models. Cellular tyrosinase activity was decreased by AN-SLP treatment in B 16 melanoma cells through dose dependent manner, but AN-SLP did not inhibit mushroom tyrosinase and L-DOPA oxidation directly. AN-SLP showed melanin inhibition by 53.2% at 50 ${\mu}g/m{\ell}$ which was 0.7 times more efficient than the antimelanogenic effect of commercial arbutin and kojic acid (36.5%) also did not show cell toxicity. Additionally, AN-SLP inhibited the activity of ${\alpha}$-glucosidase and the glycosylation of tyrosinase in melanoma cell. The resulting unsaturated glycosylation of tyrosinase makes it unstable and disturb correct transportation. From theses results, we conclude that AN-SLP could be used as anti-melanogenic agent for skin whitening.

• Korean Journal of Microbiology
• /
• v.9 no.3
• /
• pp.103-120
• /
• 1971

We have been studied on brewing sweet starch. We obtained the results as follows ; 1) 5 strains, T-T-2, T-T-4, T-K-2, T-T-18, T-T-1, were the most available in view of fermentative power by capacity of $CO_2$. 2) 5 strains, T-T-4, T-T-2, T-T-1, T-T-3, T-K-2, produced capacity of alcohol more than 5.78%. 3) 6 strains, T-T-2, T-K-2, T-T-4, T-S-2, T-I-3, T-I-1, are available not only taste and flavour, but productive power of alcohol in sweet potato starch. 4) The form of 6 strains are long oval and round and most of them are similar to the other yeast in size. 5) In giant colony the color was cream color and cream buff, and T-K-2 was formed by $15{\times}12mm$ on diameter and by 3.5mm on high. 6) Optimum temperature of most of all strains is 25~ $300^{\circ}C$but T-K-4 is 28-30.deg.C. 7) Optimum pH is 3.4-4.6. 8) T-S-2 was died off at 65.deg.C, the other strains died $60^{\circ}C$. 9( Making Bun-kok with non-heated wheat bran .alpha.-amylase was more increased by 4.5-13.5 mg of glucose in reaction solution and .betha.-amylase more 1.6-3.4ml of N/10-$KMnO_4$ Solution than Bun-kok with heated wheat bran. 10) It seems that mycellium grows better than original in substance containing 0.4 ~ 1.2% of HCl. 11) Making Bun-kok to add 0.8% HCl, .alpha.-amylase was increased 9.93-20.7mg of glucose and .betha.-amylase ws increased 2.6~4.3ml of N/10-$KMnO_4$ solution to reaction solution. 12) 1.2%-HCl, or higher concentration, acts as inhibitor, in the meanwhile the concentration between 0.4~0.8% of HCl acts as activator. 13) We must make Bun-kok for 42 hours, at 28~$30^{\circ}C$) After we made Bun-kok using S-O-II and R-J-I one by one, Bun-kok which mix each other in equal quantity is increased more than original on enzyme acrivity. 15) Oxidation is the best way of refining sweet potato starch in N/10-phosphate buffer solution (pH 7.5). 16) When we prepared sweet potato starch, first pH was 3.0.

• Korean Journal of Materials Research
• /
• v.6 no.8
• /
• pp.817-824
• /
• 1996

Removal of Cu impurities on Si substrates using remote H-plasma was investigated. Si substrates were intentionally contaminated by 1ppm ${CuCI}_{2}$, standard chemical solution. To determine the optimal process condition, remote H-plasma cleaning was conducted varying the parameters of rf power, cleaning time and remoteness(the distance between the center of plasma and the surface of Si substrate). After remote H-plasma cleaning was conducted, Si surfaces were analysed by TXRF(total x-ray reflection fluorescence) and AFM(atomic force microscope). The concentration of Cu impurity was reduced by more than a factor of 10 and its RMS roughness was improved by more than 30% after remote H-plasma cleaning. TXRF analysis results show that remote H-plasma cleaning is effective in eliminating Cu impurity on Si surface when it is performed under the optimal process condition. AFM analysis results also verifies that remote H-plasma cleaning makes no damage to the Si surface. The deposition mechanism of Cu impurity may be explained by the redox potential(oxidation-reduction reaction potential) theory. Based on the XPS analysis results we could draw a conclusion that Cu impurities on the Si substrate are removed together with the oxide by a "lift-off" mechanism when the chemical oxide( which forms when Cu ions are adsorbed on the Si surface) is etched off by reactive hydrogen atoms.gen atoms.

• Korean Journal of Materials Research
• /
• v.21 no.11
• /
• pp.587-591
• /
• 2011

The effect of the precipitator (NaOH, $NH_4OH$) and the amount of the precipitator (150, 200, 250, 300 ml) on the formation of $Fe_3(PO_4)_2$, which is the precursor used for cathode material $LiFePO_4$ in Li-ion rechargeable batteries was investigated by the co-precipitation method. A pure precursor of olivine $LiFePO_4$ was successfully prepared with coprecipitation from an aqueous solution containing trivalent iron ions. The acid solution was prepared by mixing 150 ml $FeSO_4$(1M) and 100 ml $H_3PO_4$(1M). The concentration of the NaOH and $NH_4OH$ solution was 1 M. The reaction temperature (25$^{\circ}C$) and reaction time (30 min) were fixed. Nitrogen gas (500 ml/min) was flowed during the reaction to prevent oxidation of $Fe^{2+}$. Single phase $Fe_3(PO_4)_2$ was formed when 150, 200, 250 and 300 ml NaOH solutions were added and 150, 200 ml $NH_4OH$ solutions were added. However, $Fe_3(PO_4)_2$ and $NH_4FePO_4$ were formed when 250 and 300 ml $NH_4OH$ was added. The morphology of the $Fe_3(PO_4)_2$ changed according to the pH. Plate-like lenticular shaped $Fe_3(PO_4)_2$ formed in the acidic solution below pH 5 and plate-like rhombus shaped $Fe_3(PO_4)_2$ formed around pH 9. For the $NH_4OH$, the pH value after 30 min reaction was higher with the same amount of additions of NaOH and $NH_4OH$. It is believed that the formation mechanism of $Fe_3(PO_4)_2$ is quite different between NaOH and $NH_4OH$. Further investigation on this mechanism is needed. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the pH value was measured by pH-Meter.

• Journal of the Korean Wood Science and Technology
• /
• v.33 no.1 s.129
• /
• pp.48-57
• /
• 2005

Phthalate esters are known as plasticizers and some of them suspected as endocrine disrupting chemicals. In this study, in order to identify the mechanism of phthalate esters degradation by white rot fungus, phthalic acid, which is major metabolite in the biodegradation of phthalate esters, was used. Phthalic acid 50 ppm was treated in culture medium with Polyporus brumalis. The availability of ABTS oxidation was different from control and phthalic acid treated group after 4 days of incubation. The activity was gradually increased in control group, but not in phthalic acid treated group. Especially, esterase activity of control group was maximized at 10 days of incubation, and then decreased while the activity of phthalic acid treated group was increased. Glucose was used as a carbon source, and the difference of glucose consumption by control and phthalic acid treated group was not significant. However, after 6 days of incubation the residual glucose in culture medium was rapidly decreased. The consumption rate of phthalic acid treated group was lower than control. These results might indicate that the absorption of phthalic acid in culture medium was occurred by mycelium and metabolized through some pathways as that of glucose was. To clearify the chemical modification of phthalic acid in culture medium, phthalic acid was reacted under in vitro condition which mycelium was excluded. The metabolites were analyzed by GC/MS. The results showed that phthalic acid was converted to phthalic acid anhydride by the extracellular enzymes of P. brumalis.

• Korean Journal of Soil Science and Fertilizer
• /
• v.35 no.1
• /
• pp.59-67
• /
• 2002

A phosphate solubilizing bacterium. strain 60-2G, possessing a strong ability to solubilize insoluble phosphate was isolated from the rhizosphere of grass. On the basis of GC-FAME profile, carbon utilization pattern, and the DNA sequence of a conserved partial 16S rRNA gene, the 60-2G was identified as Enterobacter intermedium. The analysis by HPLC revealed that the strain 60-2G produced mainly gluconic and 2-ketogluconic acids with small amounts of lactic acid in broth culture medium containing hydroxyapatite. During the incubation period of the strain 60-2G in broth culture, pH of the medium decreased upto 3.8 while the soluble phosphate concentration increased. The reversed correlation between pH and soluble phosphate concentration indicated that the solubility of P was due to the produced organic acids. The sequence homology of the deduced amino acids suggested that E. intermedium 60-2G synthesized PQQ which is essential for the oxidation of glucose by glucose dehydrogenase.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.20 no.1
• /
• pp.93-97
• /
• 2006

To investigate whether GyeongshinhaeGihwan 1(GGT1), an anti-obesity herbal medicine widely used in oriental medicine, regulates the expression of obesity-related genes, we measured the changes in mRNA levels of these genes by GGT1 in human growth hormone transgenic (hGHTg) obese male rats, and these effects by GGT1 were compared with those of reductil (RD), an anti-obesity drug approved by FDA. Rats received once daily oral administrations of autoclaved water, RD, or GGT1 for 8 weeks. At the end of study, rats were sacrificed and tissues were harvested. Total RNA from adipose tissue, liver and kidney was prepared and the mRNA levels for LPL (lipoprotein lipase), PPAR $\gamma$ (peroxisome proliferator activated receptor-gamma), PPAR$\delta$ (peroxisome proliferator activated receptor-delta), leptin, TNF$\alpha$ (tumor necrosis factor-alpha), and internal standard G3PDH (glyceraldehyde-3- phosphate dehydrogenase) were analyzed by RT-PCR. PPAR$\gamma$ mRNA levels of liver and kidney were decreased in drug-treated groups compared with control group and the decrease of PPAR$\gamma$ expression was more prominent in GGT1 group than in RD group, suggesting that GGT1 is effective in the inhibition of adipogenesis and lipid storage by decreasing the PPAR$\gamma$ expression. In contrast, PPAR$\delta$ mRNA levels of adipose tissue and kidney were increased by RD and GGT1 , and the magnitudes of increase were higher in GGT1 group than in RD group, indicating that GGT1 stimulates fatty acid oxidation and energy metabolism by activating PPAR$\delta$ expression, Compared with control and RD groups, GGT1 group had higher concentrations of serum leptin, a well-known inhibitor of appetite. However, The mRNA levels of leptin, LPL, and TNF$\alpha$ were not changed by GGT1 and RD, compared with DW. These results demonstrate that GGT1 not only decreases PPAR$\gamma$ expression of liver and kidney, but also increases PPAR$\delta$ expression of adipose tissue and kidney, leading to the regulation of obesity and that these effects were more pronounced in GGT1 group compared with RD group. In addition, GGT1 seems to prevent obesity by increasing the serum leptin levels.