• Journal of radiological science and technology
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• v.33 no.3
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• pp.179-184
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• 2010

A hard X-ray microscope system for obtaining images of nano-spatial resolution has been widely studied and requires monochromatic X-ray. A multilayer mirror of 84% reflectivity was designed to acquire tungsten characteristic X-ray of 8.4 keV from the white beam generated from an X-ray tube, and the C/W multilayer mirror of $50{\times}50\;mm$ size and 5.65 nm d-spacing was fabricated by the ion-beam sputtering system. The C/W multilayer had a uniformity of 99.5%, and the structure of the multilayer mirror was verified by a TEM image. The obtainable x-ray reflectivity for the C/W multilayer mirror at 8.4 keV was estimated from measuring the X-ray reflectivity using the copper characteristic X-ray of 8.05 keV. Monochromatic X-ray of 8.4 keV was generated by combining a X-ray tube, and the reflectivity and monochromaticity were 77.1% and 0.21 keV, respectively. Monochromatic X-ray generated from the combination of an X-ray tube and an C/W multilayer mirror has enough potential to use X-ray source for hard X-ray microscope system of laboratory size. If the C/W multilayer mirror of d-spacing of a few nanometers can be fabricated, monochromatic X-ray corresponded to 17.5 keV, molybdenum characteristic X-ray, can be obtained and applied to mammography in the medical application.

• 한국해양학회지
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• v.27 no.2
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• pp.91-100
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• 1992

For the study on the structure and characteristics of the primary production system in the southern waters of the East Sea, chlorophyll, phytoplankton standing stocks. nutrients and hydrographic properties were investigated and analyzed in conjunction with measurement of C-14 based primary productivity. The primary productivity was relatively high in comparison with the previous studies, ranging from 284 to 4,574 mgC$.$m/SUP -2/$.$day /SUP -1/ and averaged to be 2,000 mgC$.$m/SUP 02/$.$day/SUP -1/. The standing stocks within the euphotic zone were fairly high, but ambient inorganic nitrogenous nutrient concentrations were too low to support the high production. This implied that there might be active recycling of nitrogenous nutrients by heterotrophic processes and the upward flux of nutrients by vertical mixing. Subsurface chlorophyll maxima were continuously observed in the lower parts of the euphotic layer and the depth coincided with the nutricline rather than isopycnal surfaces, supporting the view that chlorophyll distributions and primary production were primarily influenced by nutrient supply. Despite low nutrient concentrations, phytoplankton standing stocks and production were fairly high and the fraction of autotrophic nano- and picoplankton production was significant.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.199-204
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• 2000

In this study, the ZnS nanosized thin films that could be used for fabrication of blue light-emitting diodes, electro-optic modulators, and n-window layers of solar cells were grown by the solution growth technique (SGT), and their structural and optical properties were examined. Based on these results, the quantum size effects of ZnS were systematically investigated. Governing factors related to the growth condition were the concentration of precursor solution, growth temperature, concentration of aq. ammonia, and growth duration. X-ray diffraction patterns showed that the ZnS thin film obtained in this study had the cubic structure ($\beta$-ZnS). When the growth temperature was $75^{\circ}C$, the surface morphology and the grain size uniformity were the best. The energy band gaps of samples were determined from the optical transmittance valued, and were shown to vary from 3.69 eV to 3.91 eV. These values were substantially higher than 3.65 eV of bulk ZnS, demonstrating that the quantum size effect of SGT grown ZnS is remarkable. Photoluminescence (PL) peaks were observed at the positions corresponding to the lower energy than that to energy band gap, illustrating that the surface states were induced by the ultra-fineness of grains in ZnS films. Particularly, for the first time, it is reported for the SGT grown ZnS that the PL peaks were shifted depending on the grain size.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.479-485
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• 2006

The double gate(DG) MOSFET is a promising candidate to further extend the CMOS scaling and provide better control of short channel effect(SCE). DGMOSFETs, having ultra thin undoped Si channel for SCEs control, ale being validated for sub-20nm scaling. A novel analytical transport model for the subthreshold mode of DGMOSFETs is proposed in this paper. The model enables analysis of short channel effect such as the subthreshold swing(SS), the threshold voltage roil-off$({\Delta}V_{th})$ and the drain induced barrier lowering(DIBL). The proposed model includes the effects of thermionic emission and quantum tunneling of carriers through the source-drain barrier. An approximative solution of the 2D Poisson equation is used for the distribution of electric potential, and Wentzel-Kramers-Brillouin approximation is used for the tunneling probability. The new model is used to investigate the subthreshold characteristics of a double gate MOSFET having the gate length in the nanometer range $(5-20{\sim}nm)$ with ultra thin gate oxide and channel thickness. The model is verified by comparing the subthreshold swing and the threshold voltage roll-off with 2D numerical simulations. The proposed model is used to design contours for gate length, channel thickness, and gate oxide thickness.

• Journal of the Mineralogical Society of Korea
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• v.19 no.2 s.48
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• pp.81-88
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• 2006

The Yttria Partially Stabilized Zirconia powder was prepared by spontaneous precipitation method using $ZrOCl_2{\cdot}8H_O-YCl_33{\cdot}6H_2O$ solution as a starting materials. The optimal experimental conditions such as concentration and pH of starting solutions, the amounts of stabilizer $Y_2O_3$ used, and sintered temperature were carefully studied. The best condition for synthesizing $ZrO_2$ was experimentally selected and applied throughout this study for the preparation of the 3 mole% $Y_2O_3$ partially stabilized zirconia, 3YSZ. The physical properties of 3YSZ was examined by XRD, Raman, DT A, and SEM. The structural transition from pure monoclinic high temperature $ZrO_2$ to tetragonal room temperature 3YSZ was made possible by the added amount of $Y_2O_3$ in the $ZrO_2+Y_2O_3$ system. All Raman Spectrum band appeared in the lower wave numbers rather than in higher wave numbers as structure changes from monoclinic to tetragonal.

• KSBB Journal
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• v.23 no.1
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• pp.44-47
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• 2008

Anthracycline antibiotics doxorubicin (DXR) is clinically important cancer therapeutic agent produced by Streptomyces peucetius. DXR result by further metabolism of rhodomycin D (RHOD) and require a deoxy-sugar component for their biological activity. In this study, production of TDP-L-daunosamine and its attachment to ${\varepsilon}$-rhodomycinone (RHO) to generate RHOD has been achieved by bioconversion in Streptomyces venezuelae that bears eleven genes. S. peucetius seven genes (dnmUTJVZQS) were transformed by plasmid and S. venezuelae two genes desIII, IV and two more S. peucetius drrA, B genes were integrated into chromosomal DNA. To generate the feeding substrate RHO, 6L S. peucetius grown on agar plate was harvested, extracted with organic solvent and then purified using preparative HPLC. Recombinant S. venezuelae grown on agar plate containing RHO was harvested and its n-butanol soluble components were extracted. The glycosylated product of aromatic polyketide RHO using heterologous host S. venezuelae presents the minimal information for TDP-L-daunosamine biosynthesis and its attachment onto aglycone. Moreover, the structure of auxiliary protein, DnrQ, was predicted by fold recognition and homology modeling in this study. This is a general approach to further expand of new glycosides of antitumor anthracycline antibiotics.

• Journal of the Korean Vacuum Society
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• v.22 no.1
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• pp.37-44
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• 2013

In order to investigate an influence of carrier trap by quantum dots (QDs) on the solar parameters, in this study, the $p^+-QD-n/n^+$ solar cells with InAs/GaAs QD active layers are fabricated, and their characteristics are investigated and compared with those of a GaAs matrix solar cell (MSC). Two different types of QD structures, the Stranski-Krastanow (SK) QD and the quasi-monolayer (QML) QD, have been introduced for the QD solar cells, and the parameters (open-circuit voltage ($V_{OC}$), short-cirucuit current ($I_{SC}$), fill factor (FF), conversion efficiency (CE)) are determined from the current-voltage characteristic curves under a standard solar illumination (AM1.5). In SK-QSC, while FF of 80.0% is similar to that of MSC (80.3%), $V_{OC}$ and $J_{SC}$ are reduced by 0.03 V and $2.6mA/cm^2$, respectively. CE is lowered by 2.6% as results of reduced $V_{OC}$ and $J_{SC}$, which is due to a carrier trap into QDs. Though another alternative structure of QML-QD to be expected to relieve the carrier trap have been firstly tried for QSC in this study, it shows negative results contrary to our expectations.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.433-439
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• 2012

In this study, a cationic surfactant BHMAS (N,N-bis-(3'-n-dodecyloxy-2'-hydroxypropyl)-N-methyl-2-hydroxyethylammonium methyl sulfate) having two lauryl and three hydroxyl groups was synthesized by the reaction of n-dodecyl glycidyl ether and 2-aminoethanol followed by the quarternization with dimethyl sulfate. The structure of the product was elucidated by $^{1}H-NMR$ and FT-IR. The CMC (critical micelle concentration) and surface tension of BHMAS at CMC condition were found to be $9.12\;{\times}\;10^{-4}$ mol/L and 28.71 mN/m respectively. Dynamic surface tension measurements using a maximum bubble pressure tensiometer indicated that a relatively long time was required to saturate the interface between air and aqueous surfactant solution. The interfacial tension measured between 1 wt% surfactant solution and n-decane reached an equilibrium value of 0.045 mN/m in 5 min. The adsorption capacity of the synthesized surfactant was observed to be excellent, which suggests that the surfactant can be used as a softening agent during a laundry process.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.134-134
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• 2011

High-k dielectric materials such as $HfO_2$, $ZrO_2$ and $Al_2O_3$ increase gate capacitance and reduce gate leakage current in MOSFET structures. This behavior suggests that high-k materials will be promise candidates to substitute as a tunnel barrier. Furthermore, stack structure of low-k and high-k tunnel barrier named variable oxide thickness (VARIOT) is more efficient.[1] In this study, we fabricated the $WSi_2$ nanocrystals nonvolatile memory device with $SiO_2/HfO_2/Al_2O_3$ tunnel layer. The $WSi_2$ nano-floating gate capacitors were fabricated on p-type Si (100) wafers. After wafer cleaning, the phosphorus in-situ doped poly-Si layer with a thickness of 100 nm was deposited on isolated active region to confine source and drain. Then, on the gate region defined by using reactive ion etching, the barrier engineered multi-stack tunnel layers of $SiO_2/HfO_2/Al_2O_3$ (2 nm/1 nm/3 nm) were deposited the gate region on Si substrate by using atomic layer deposition. To fabricate $WSi_2$ nanocrystals, the ultrathin $WSi_2$ film with a thickness of 3-4 nm was deposited on the multi-stack tunnel layer by using direct current magnetron sputtering system [2]. Subsequently, the first post annealing process was carried out at $900^{\circ}C$ for 1 min by using rapid thermal annealing system in nitrogen gas ambient. The 15-nm-thick $SiO_2$ control layer was deposited by using ultra-high vacuum magnetron sputtering. For $SiO_2$ layer density, the second post annealing process was carried out at $900^{\circ}C$ for 30 seconds by using rapid thermal annealing system in nitrogen gas ambient. The aluminum gate electrodes of 200-nm thickness were formed by thermal evaporation. The electrical properties of devices were measured by using a HP 4156A precision semiconductor parameter analyzer with HP 41501A pulse generator, an Agillent 81104A 80MHz pulse/pattern generator and an Agillent E5250A low leakage switch mainframe. We will discuss the electrical properties for application next generation non-volatile memory device.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.288-289
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• 2011

Indium Tin Oxide (ITO) is a typical highly Transparent Conductive Oxide (TCO) currently used as a transparent electrode material. Most widely used deposition method is the sputtering process for ITO film deposition because it has a high deposition rate, allows accurate control of the film thickness and easy deposition process and high electrical/optical properties. However, to apply high quality ITO thin film in a flexible microelectronic device using a plastic substrate, conventional DC magnetron sputtering (DMS) processed ITO thin film is not suitable because it needs a high temperature thermal annealing process to obtain high optical transmittance and low resistivity, while the generally plastic substrates has low glass transition temperatures. In the room temperature sputtering process, the electrical property degradation of ITO thin film is caused by negative oxygen ions effect. This high energy negative oxygen ions(about over 100eV) can be critical physical bombardment damages against the formation of the ITO thin film, and this damage does not recover in the room temperature process that does not offer thermal annealing. Hence new ITO deposition process that can provide the high electrical/optical properties of the ITO film at room temperature is needed. To solve these limitations we develop the Magnetic Field Shielded Sputtering (MFSS) system. The MFSS is based on DMS and it has the plasma limiter, which compose the permanent magnet array (Fig.1). During the ITO thin film deposition in the MFSS process, the electrons in the plasma are trapped by the magnetic field at the plasma limiters. The plasma limiter, which has a negative potential in the MFSS process, prevents to the damage by negative oxygen ions bombardment, and increases the heat(-) up effect by the Ar ions in the bulk plasma. Fig. 2. shows the electrical properties of the MFSS ITO thin film and DMS ITO thin film at room temperature. With the increase of the sputtering pressure, the resistivity of DMS ITO increases. On the other hand, the resistivity of the MFSS ITO slightly increases and becomes lower than that of the DMS ITO at all sputtering pressures. The lowest resistivity of the DMS ITO is $1.0{\times}10-3{\Omega}{\cdot}cm$ and that of the MFSS ITO is $4.5{\times}10-4{\Omega}{\cdot}cm$. This resistivity difference is caused by the carrier mobility. The carrier mobility of the MFSS ITO is 40 $cm^2/V{\cdot}s$, which is significantly higher than that of the DMS ITO (10 $cm^2/V{\cdot}s$). The low resistivity and high carrier mobility of the MFSS ITO are due to the magnetic field shielded effect. In addition, although not shown in this paper, the roughness of the MFSS ITO thin film is lower than that of the DMS ITO thin film, and TEM, XRD and XPS analysis of the MFSS ITO show the nano-crystalline structure. As a result, the MFSS process can effectively prevent to the high energy negative oxygen ions bombardment and supply activation energies by accelerating Ar ions in the plasma; therefore, high quality ITO can be deposited at room temperature.