• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3383-3386
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• 2012

SnS thin films were deposited on glasses through metal organic chemical vapor deposition (MOCVD) method at relatively mild conditions, using bis(3-mercapto-1-propanethiolato) tin(II) precursor without toxic $H_2S$ gas. The MOCVD process was carried out in the temperature range of $300-400^{\circ}C$ and the average grain size in fabricated SnS films was about 500 nm. The optical band gap of the SnS film was about 1.3 eV which is in optimal range for harvesting solar radiation energy. The precursor and SnS films were characterized through infrared spectroscopy, nuclear magnetic resonance spectroscopy, DIP-EI mass spectroscopy, elemental analyses, thermal analysis, X-ray diffraction, and field emission scanning electron microscopic analyses.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.4
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• pp.27-39
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• 2015

This study addressed the process to construct, operate, verify the test beds, which had been equipped with a variety of core technologies such as WAVE, Road-Radar, Smart Tolling developed by Smart Highway Project. We have met our research goals, but there were limitations to secure the performance and user feedback because of small scale and short operating time. So, we will enhance user safety, convenience and comfort by accumulating and analyzing big data then improving testbeds and related technologies through subsequent research projects for a long time.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.348-351
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• 1995

A modified silicon direct bonding method has been developed alloying an intimate contact between grooved and smooth mirror-polished oxide-free silicon wafers. A regular set of grooves was formed during preparation of heavily doped $p^+$-type grid network by oxide-masking und boron diffusion. Void-free bonded interfaces with filing of the grooves were observed by x-ray diffraction topography, infrared, optical. and scanning electron microscope techniques. The presence of regularly formed grooves in bending plane results in the substantial decrease of dislocation over large areas near the interface. Moreover two strongly misoriented waters could be successfully bonded by new technique. Diodes with bonded a pn-junction yielded a value of the ideality factor n about 1.5 and the uniform distribution of series resistance over the whole area of horded pn-structure. The suitability of the modified technique was confirmed by I - V characteristics of power diodes and reversly switched-on dynistor(RSD) with a working area about $12cm^2$. Both devices demonstrated breakdown voltages close to the calculation values.

• Journal of the Korean institute of surface engineering
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• v.41 no.4
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• pp.129-133
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• 2008

Nitrogen and aluminum codoped ZnO(NAZO) thin films were grown on glass substrates with changing the nitrogen flow ratio by radio-frequency magnetron sputtering. The structural, optical, and electrical properties of the NAZO films were investigated. The surface morphologies and the structural properties of the thin films were analyzed by using the X-ray diffraction and scanning electron microscopy. The NAZO thin film, deposited at nitrogen flow ratio of 0%, showed a strongly c-axis preferred orientation and the lowest resistivity of $3.2{\times}10^{-3}{\Omega}cm$. The intensity of ZnO(002) diffraction peak was decreased gradually with increasing the nitrogen flow ratio. The optical properties of the films were measured by UV-VIS spectrophotometer and the optical transmittances for all the samples were found to be an average 90% in the visible range. Based on the transmittance value, the optical bandgap energy for the NAZO thin film deposited at nitrogen flow ratio of 0% was determined to be 3.46 eV. As for the electrical properties, the carrier concentration and the hall mobility were decreased, but the electrical resistivity was increased as the nitrogen flow ratio was increased.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.118-122
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• 2009

Organic thin film transistors with a pentacene active layer and various polymer gate insulators were fabricated and their performances were investigated. Characteristics of pentacene thin film transistors on different polymer substrates were investigated using an atomic force microscope (AFM) and x-ray diffraction (XRD). The pentacene thin films were deposited by thermal evaporation on the gate insulators of various polymers. Hexamethyldisilazane (HMDS), polyvinyl acetate (PVA) and polymethyl methacrylate (PMMA) were fabricated as the gate insulator where a pentacene layer was deposited at 40, 55, 70, 85, 100 oC. Pentacene thin films on PMMA showed the largest grain size and least trap concentration. In addition, pentacene TFTs of top-contact geometry are compared with PMMA and $SiO_2$ as gate insulators, respectively. We also fabricated pentacene TFT with Poly (3, 4-ethylenedioxythiophene)-Polysturene Sulfonate (PEDOT:PSS) electrode by inkjet printing method. The physical and electrical characteristics of each gate insulator were tested and analyzed by AFM and I-V measurement. It was found that the performance of TFT was mainly determined by morphology of pentacene rather than the physical or chemical structure of the polymer gate insulator

• Journal of Powder Materials
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• v.17 no.1
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• pp.7-12
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• 2010

In this work, effect of various process-control agents (PCAs) on the mechanical alloying of amorphous alloy of $Al_{85}Y_8Ni_5Co_2$ has been investigated. The dependence of the particle shape, size and crystallization behavior of the amorphous alloy powders on the type of PCAs and their concentrations was investigated by using X-ray diffraction, field-emission scanning electron microscopy and differential scanning calorimetry. It was found that the additive of toluene could affect positively the amorphization and thermally induced crystallization processes, as well as the size refinement, morphology and particle-size distribution of as-milled powders in comparison with alloy obtained without PCA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.6
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• pp.480-485
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• 2011

ZnO is an n-type semiconductor with a wide band gap near 3.37 eV. It was known that ZnO films with a resistivity of the order of $10^{-4}\;{\Omega}cm$ is not easy to obtain. 1, 3, and 5wt% Si element were added into ZnO in ordre to improve the electrical and optical characteristics. The Si-doped ZnO (SZO) was grown on a glass substrate by radio frequency (RF) magnetron sputtering at the temperature range from 100 to $500^{\circ}C$. X-ray diffraction (XRD) patterns of SZO film showed preferable crystal orientation of (002) plane. It was confirmed that the lowest resistivity of the SZO films was $2.44{\times}10^{-3}{\Omega}cm$ and SZO films were significantly influenced by the working temperature. The average transmittance of the films was over 80% in the visible ranges.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.42.1-42.1
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• 2017

We present the results from an extensive spectroscopic survey of the central region of the nearby galaxy cluster Abell 2199 (A2199) at z=0.03. By combining 775 new redshifts from the MMT/Hectospec observations with the data in the literature, we construct a large sample of 1624 galaxies with measured redshifts at R<30', which redsults in high spectroscopic completeness at $r_{petro,0}$<20.5 (77%). We use these data to study the kinematics and clustering of galaxies, focusing on the comparison with those of the intracluster medium (ICM) from Suzaku X-ray observations. We identify 406 member galaxies of A2199 at R<30' using the caustic technique. The velocity dispersion profile of cluster members appears smoothly connected to the stellar velocity dispersion profile of the cD galaxy. The luminosity function is well fitted with a Schechter function at $M_r$<-15. The radial velocities of cluster galaxies generally agree well with those of the ICM, but there are some regions where the velocity difference between the two is about a few hundred kilometers per second. The cluster galaxies show a hint of global rotation at R<5' with $v_{rot}=300-600kms^{-1}$, but the ICM in the same region does not show such rotation. We apply a friends-of-friends algorithm to the cluster galaxy sample at R<60' and identify 32 group candidates, and examine the spatial correlation between the galaxy groups and X-ray emission. This extensive survey in the central region of A2199 provides an important basis for future studies of interplay among the galaxies, the ICM, and the dark matter in the cluster.

• BMB Reports
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• v.38 no.5
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• pp.624-631
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• 2005

Tuberculosis, caused by Mycobacterium tuberculosis, continues to be one of the main diseases to mankind. It is urgent to discover novel drug targets for appropriate antimicrobial agents against this human pathogen. The shikimate pathway is onsidered as an attractive target for the discovery of novel antibiotics for its essentiality in bacteria and absence in mammalian cells. The Mycobacterium tuberculosis aroE-encoded shikimate dehydrogenase was cloned, expressed and purified. Sequence alignment analysis shows that shikimate dehydrogenase of Mycobacterium tuberculosis exhibit the pattern of G-X-(N/S)-V-(T/S)-X-PX-K, which is highly conserved within the shikimate dehydrogenase family. The recombinant shikimate dehydrogenase spectrum determined by CD spectroscopy showed that the percentages for $\alpha$-helix, $\beta$-sheet, $\beta$-turn, and random coil were 29.2%, 9.3%, 32.7%, and 28.8%, respectively. The enzymatic characterization demonstrates that it appears to be fully active at pH from 9.0 to 12, and temperature $63^{\circ}C$. The apparent Michaelis constant for shikimic acid and $NADP^+$ were calculated to be about $29.5\;{\mu}M$ and $63\;{\mu}M$. The recombinant shikimate dehydrogenase catalyzes the substrate in the presence of $NADP^+$ with an enzyme turnover number of $399\;s^{-1}$. Zymological studies suggest that the cloned shikimate dehydrogenase from M. tuberculosis has a pretty activity, and the work should help in the discovery of enzyme inhibitors and further of possible antimicrobial agents against Mycobacterium tuberculosis.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2503-2508
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• 2010

ZnO thin films were grown on Si or $SiO_2$/Si substrates, at growth temperatures ranging from 150 to $400^{\circ}C$, by atomic layer deposition (ALD) using diethylzinc and water. Despite the large band gap of 3.3 eV, the ALD ZnO films show high n-type conductivity, i.e. low resistivity in the order of $10^{-3}\;{\Omega}cm$. In order to understand the high conductivity of ALD ZnO films, the films were characterized with X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, elastic recoil detection, Rutherford backscattering, Photoluminescence, and Raman spectroscopy. In addition, the various analytical data of the ZnO films were compared with those of ZnO single crystal. According to our analytical data, metallic zinc plays an important role for the high conductivity in ALD ZnO films. Therefore when the metallic zinc was additionally oxidized with ozone by a modified ALD sequence, the resistivity of ZnO films could be adjusted in a range of $3.8{\times}10^{-3}\;{\sim}\;19.0\;{\Omega}cm$ depending on the exposure time of ozone.