• Korean Journal of Materials Research
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• v.10 no.12
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• pp.807-811
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• 2000

CeO$_2$ and SrBi$_2$Ta$_2$O$_{9}$ (SBT) thin films for MFISFET (Metal-ferroelectric-insulator-semiconductor-field effect transistor) were deposited by r.f. sputtering and pulsed laser ablation method, respectively. The effects of sputtering gas ratio(Ar:O$_2$) during deposition for CeO$_2$ films were investigated. The CeO$_2$ thin films deposited on Si(100) substrate at $600^{\circ}C$ exhibited (200) preferred orientation. The preferred orientation, Brain size and surface roughness of films decreased with increasing oxygen to argon gas ratio. The films deposited under the condition of Ar:O$_2$= 1 : 1 showed the best C- V characteristics. The leakage current of films showed the order of 10$^{-7}$ ~10$^{-8}$ A at 100kV/cm. The SBT thin films on CeO$_2$/Si substrate showed dense microstructure of polycrystalline phase. From the C-V characteristics of MFIS structure with SBT film annealed at 80$0^{\circ}C$, the memory window width was 0.9V at 5V The leakage current density of Pt/SBT/CeO$_2$/Si structure annealed at 80$0^{\circ}C$ was 4$\times$10$^{-7}$ /$\textrm{cm}^2$ at 5V.

• Environmental Mutagens and Carcinogens
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• v.22 no.2
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• pp.106-111
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• 2002

AG6O, the complex of acriflavine and guanosine, has been shown to possess the synergistic antitumorigenic activity in the previous paper (J. Pharm. Pharmacol. 1997, 49:216). In this study, we have investigated the genotoxic properties of AG60 using in vitro and in vivo system such as Ames bacterial reversion test, chromosomal aberration assay and micronucleus assay. In Ames reverse mutation test, AG60 treatment at the dose range up to 250 $\mu\textrm{g}$/plate caused the dose-independent random induction of the mutagenic colony formation in S. typhimurium TA98, TA100, TA1537, and E. coli WP2uvrA, while any mutagenic effect of AG60 wasn't observed in S. typhimurium TA1535. Any significant chromosomal aberration wasn't observed in chinese hamster lung (CHL) fibroblast cells incubated with PBS or AG60 at the concentrations of 2.5, 5, 10 $\mu\textrm{g}$/$m\ell$ for 24 hours without but even with 59 metabolic activation system for 6 hours. In vivo ICR mice, the intramuscular injection of AG60 at the doses of 7.15, 14.3, and 28.6 mg/kg did not induce the frequency of micronucleus formation. However, mitomycin C, as one of the positive controls at the dose of 2 mg/kg caused the 8.4% induction in the frequency of micronucleus and 24% increase in the chromosomal aberration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.772-775
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• 2004

본 논문에서는 $B_2O_3$ 첨가가 Ba$(Mg_{1/3}Ta_{2/3})O_3$ (BMT)의 유전특성 및 미세구조의 변화에 미치는 영향에 대해 연구하였다 $B_2O_3$가 소량 첨가되었을 때는 결정립의 성장을 야기하여 치밀한 미세구조를 보였지만, 다량이 첨가된 경우 비정상 결정립 성장을 야기하여 치밀화가 떨어지는 미세구조를 보임과 동시에 $Ba_3Ta_5O_{15}$의 2차상을 형성했다. 이는 소량의 $B_2O_3$ 첨가가 유전특성의 향상을 가져왔지만, 다량의 첨가는 오히려 특성의 악화를 가져온 결과의 원인이라 생각된다. 0.5mol%의 $B_2O_3$를 첨가하여 $1500^{\circ}C$에서 6시간 소결한 경우 ${{\varepsilon}_r}=24$, $Q{\times}f=210,000GHz$의 유전 특성 값과 $4.74ppm/^{\circ}C$의 $T_{cf}$ 값을 얻었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.2
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• pp.143-150
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• 2000

Ferroelectric SrxBi2+yTa2O9+$\alpha$ thin films with various compositions(x=0.7, 0.8, 1, y=0.3, 0.4) were prepared by sol-gel method. The film with moled ratio of 0.8:2.3:2.0 in Sr/Bi/Ta, which was deposited on Pt/SiO2/Si (100), showed better ferroelectric properties than other films. To investigate substrate effects, the same compositions were spin coated on Pt/Ti/SiO2/Si (100) substrates. At an applied voltage of 5V, the dielectric constant($\varepsilon$r), remanent polarization (2Pr) and coercive field (Ec) of the Sr0.8Bi2.3Ta2O9+$\alpha$ thin film prepared on Pt/Ti/SiO2/Si (100) were about 296, 24$\mu$C/$\textrm{cm}^2$ and Ec of 49kV/cm respectively. Both SBT films firred at 80$0^{\circ}C$ revealed no fatigue up to 1010 cycles. Retention characteristics of these capacitors showed no degradation up to 104 sec.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2003.05a
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• pp.67-67
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• 2003

The chemical compositions and textural relationships of the Nb-Zr oxide minerals including pyrochlore [ideally (Ca,Na)$_2$Nb$_2$O$\sub$6/(OH,F), with up to 24% UO$_2$ and 16% Ta$_2$O$\sub$5/] and baddeleyite [ideally ZrO$_2$, with up to 6% Nb$_2$O$\sub$5/] in the Sokli carbonatite complex, Kola Peninsula, Arctic are described. These two minerals in carbonatites are the major hosts for the HFSEs such as U, Th, Ta, Nb, Zr and Hf and thus are interest both economically and petrologically. The Sokli carbonatite complex (360-370 Ma) in Northern Finland, which forms a part of the Paleozoic Kola Alkaline Province (KAP), is mainly composed of multi-stages of carbonatite and phoscorite associations (P1-C1 P2-C2, P3-C3, D4 and D5) surrounded by altered ultramafic rocks (olivinite and pyroxenite) and cut by numerous small dikes of ultramafic lamprophyre. The Sokli complex contains the highest concentration in niobium and probably in tantalum, which are economically very important to modern steel technology, among the ultramafic-alkaline complexes of the KAP. Pyrochlore and baddeleyite mostly concentrate in the phoscorites. Pyrochlores in the Sokli complex are generally rounded octahedra and cubes in shape, red brown to grey yellow in color, and 0.2 to 5 mm in size. They are found in all calcite carbonatites, phoscorites and dolomite carbonatites, except P1-C1 rocks. These pyrochlores display remarkable zonations which depend on host rock compositions, and have significant compositional variations with evolution of the Sokli complex. The common variation scheme is that (1) early pyrochlore is highly enriched in U and Ta; (2) these elements decrease abruptly in the intermediate stage, while Th and Ce increase, and (3) late stage pyrochlore is low in U, Ta, Th, and Ce, and correspondingly high in Nb. Baddeleyites in the Sokli complex occur in the early P1-C1 and P2-C2 rocks and rarely in P3. They crystallized earlier than pyrochlores, and occasionally show post-magmatic corrosion and replacement. The FeO and TiO$_2$ contents of baddeleyites are much lower than those of the other terrestrial and lunar baddeleyites, whereas Nb$_2$O$\sub$5/ and Ta$_2$O$\sub$5/ contents are the highest among the reported compositions. Ta/Nb and Zr/Nb ratios of pyrochlores and baddeleyites decrease towards later stage facies, which is in accordance with the whole rock compositions. The variation of Ta/Nb and Zr/Nb ratios of pyrochlores and baddeleyites is considered to be a good indicator to trace an evolution of the carbonatite complexes.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.36-38
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• 2005

This study is about how to lower the driving voltage that enables to move the micro droplet by the EWOD (Electro Wetting On Dielectric) mechanism. EWOD is well known that it is used ${\mu}-TAS$ digital micro fluidics system. As the device which is fabricated with dielectric layer between electrode and micro droplet is applied voltage, the hydrophobic surface is changed into the hydrophilic surface by electrical property. Therefore, EWOD induces the movement of micro droplet with reducing contact angle of micro droplet. The driving voltage was depended on the dielectric constant of dielectric layer, thus it can be reduced by increase of dielectric constant. Typically, very high voltage ($100V{\sim}$) is used to move the micro droplet. In previous study, we used $Ta_{2}O_{5}$ as the dielectric layer and driving voltage was 23V that reduced 24 percent compared with $SiO_2$. In this study, we used $BZN(Bi_{2}O_{3}ZnO-Nb_{2}O_{5})$ layer which had high dielectric constant. It was operated the just 12V. And micro droplet was moved within Is on 15V. It was reduced the voltage until 35 percents compare with $Ta_{2}O_{5}$ and 50 percents compare with $SiO_2$. The movement of micro droplet within 1s was achieved with BZN (ferroelectrics)just on 15V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.167-170
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• 2000

The structural changes and the dielectric properties of $(Ba_{1-x}Ca_x)(Mg_{1/3}Ta_{2/3})O_3$ (x=0, 0.2, 0.4, 0.6, 0.8, 1) were investigated. The densities of samples were gradually decreased with increasing x, (BMT=7.69, CMT=5.25 $g/cm^3$). The crystal structure of BMT was a untiltied perovskite structure, however BCMT showed antiphase tilting and antiphase-inphase tilting structure. The dielectric constant($\varepsilon_r$) of the highest value was 33 at x=0.2 (BMT=24, CMT=17). The maximum quality factor was 27,500GHz in BMT. The quality factor· of BCMT was decreased to x<0.2 (5,000GHz), and was gradually increased to x>0.2. The temperature coefficients of dielectric constant was positive at x<0.8, and negative in CMT.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.24.1-24.1
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• 2009

Tantalum carbo-nitride($T_aC_xN_y$) films were deposited with chemical vapor deposition(CVD) using tert-butylimido tris-diethylamido tantalum (TBTDET, $^tBu-N=Ta-(NEt_2)_3$, $Et=C_2H_5$, $^tBu=C(CH_3)_3$) between $350^{\circ}C$ and $600^{\circ}C$ with argon as a carrier gas. Fourier transform infrared (FT-IR)spectroscopy was used to study the thermal decomposition behavior of TBTDET in the gas phase. When the temperature was increased, C-H and C-N bonding of TBTDET disappeared and the peaks of ethylene appeared above $450^{\circ}C$ in the gas phase. The growth rate and film density of $T_aC_xN_y$ film were in the range of 0.1nm/min to 1.30nm/min and of $8.92g/cm^3$ to $10.6g/cm^3$ depending on the deposition temperature. $T_aC_xN_y$ films deposited below $400^{\circ}C$ were amorphous and became polycrystal line above $500^{\circ}C$. It was confirmed that the $T_aC_xN_y$ film was a mixture of TaC, graphite, $Ta_3N_5$, TaN, and $Ta_2O_5$ phases and the oxide phase was formed from the post deposition oxygen uptake. With the increase of the deposition temperature, the TaN phase was increased over TaC and $Ta_3N_5$ and crystallinity, work function, conductivity and density of the film were increased. Also the oxygen uptake was decreased due to the increase of the film density. With the increase of the TaC phase in $T_aC_xN_y$ film, the work function was decreased to 4.25eV and with the increase of the TaN phase in $T_aC_xN_y$ film,it was increased to 4.48eV.

• Korean journal of food and cookery science
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• v.27 no.4
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• pp.17-26
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• 2011

This study was performed to analyze the antibacterial activity against food hazardous microorganisms and antimutagenic effects of Sanguisorba officinalis L. ethanol extracts on Salmonella Typhimurium TA100. The antibacterial activity was evaluated by paper disc diffusion assay, minimum inhibition concentration (MIC), and optical density of the culture with the ethanol extract for 24 hr. Antibacterial activity was tested with seven microorganisms including Escherichia coli, Escherichia coli O157:H7, Pseudomonas aeruginosa, Salmonella Typhimurium, Listeria monocytogenes, Bacillus cereus, and Staphylococcus aureus. The paper disc diffusion assay showed distinct clear inhibition zones around the discs treated with the extract for five microorganisms, except Escherichia coli and Escherichia coli O157:H7. MIC values were 0.625-2.5 mg/mL for these five strains that showed clear zones. The time-kill assay was consistent with the results from the paper disc diffusion assay and MIC test. Additionally, antimutagenicity of the extract was determined using the Ames test. The ethanol extract at 5 mg/plate inhibited 72.42% and 89.85% of mutagenicity induced by 4-nitroquinoline 1-oxide and sodium azide, respectively. These results demonstrate that the ethanol extract from S. officinalis L. has remarkable antibacterial activity and antimutagenicity.

• Nuclear Engineering and Technology
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• v.28 no.5
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• pp.458-466
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• 1996

The effects of dopants on the modification of microstructure of UO$_2$ and UO$_2$-4wt%CeO$_2$ sintered pellets have been studied in hydrogen and $CO_2$/CO mixture atmospheres by using $Ta_2O_5$, TiO$_2$ and $Nb_2O_5$ as sintering additives. The dopant were added as oxide powders and homogenized by attrition milling. The mixed powders were pressed, and then sintered in hydrogen at 1$700^{\circ}C$ , or in oxidizing atmosphere using Controlled $CO_2$/CO mixtures at 125$0^{\circ}C$. Both density and microstructure of UO$_2$ are modified by the addition of dopants in reducing atmosphere. The sintered density is increased with $Ta_2O_5$ addition up to 0.33wt% and subsequently decreased with higher content of the additive. The effect on the densification and the gain growth are apparent with the addition of 0.24wt% $Nb_2O_5$. With 0.lwt% titania and 0.6wt% $Ta_2O_5$, the sintered density is decreased, but the grain size is increased. In oxidizing atmosphere, the grain sizes for UO$_2$ doped with the above additives are smaller than that for pure UO$_2$. The grain size of Ta or Nb-doped UO$_2$ is decreased with increasing $CO_2$/CO ratio, but that of pure UO$_2$or T-doped UO$_2$ is increased. A large portion of second phases is observed in UO$_2$ doped with 0.lwt% TiO$_2$ sintered in hydrogen atmosphere, while, in $CO_2$/CO atmospheres, the second phases or dopant agglomerates are not observed. For UO$_2$-4wt%CeO$_2$ mixed oxide, the effect of additives on the gain growth is not so much as that for the pure UO$_2$. This is attributed to the formation of clusters by dopant cations and Ce ions, so that the additives contribute to a lesser exent to the grain growth for the mixed oxide.