• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.2
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• pp.49-55
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• 2001

ZnO films were fabricated on p-type Si(100) wafer ITO glass and quartz glass by the sol-gel process using zinc acetate dihydrate as starting material. A homogeneous and stable solution was prepared by dissolving the zinc acetate dihydrate in a solution of 2-methoxyethanol and monoethanolamine (MEA). ZnO films were deposited by spin-coating at 2800 rpm for 25 s and were dried on a hot plate at $250^{\circ}C$ for 10 min. Crystallization of the films was carried out at $400^{\circ}C$~$800^{\circ}C$ for 1 h in air. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), UV-vis transmittance spectroscopy, FTIR transmittance spectroscopy and Photoluminescence (PL) spectroscopy measurements have been used to study the structural and optical properties of the films. ZnO films highly oriented along the (002)plane were obtained. In all cases the films were found to be transparent (above 70%) in visible range with a sharp absorption edge at wavelengths of about 380nm, which is very close to the intrinsic band-gap of ZnO(3.2 eV). The low temperature band-edge photoluminescence revealed a complicated multi-line structure in terms of bound exciton complexes and the phonon replicas.

• Korean Journal of Materials Research
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• v.20 no.6
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• pp.289-293
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• 2010

Silicon quantum dots (Si QDs) in a superlattice for high efficiency tandem solar cells were fabricated by magnetron rf sputtering and their characteristics were investigated. SiC/$Si_{1-x}C_x$ superlattices were deposited by co-sputtering of Si and C targets and annealed at $1000^{\circ}C$ for 20 minutes in a nitrogen atmosphere. The Si QDs in Si-rich layers were verified by transmission electron microscopy (TEM) and X-ray diffraction. The size of the QDs was observed to be 3-6 nm through high resolution TEM. Some crystal Si and -SiC peaks were clearly observed in the grazing incident X-ray diffractogram. Raman spectroscopy in the annealed sample showed a sharp peak at $516\;cm^{-1}$ which is an indication of Si QDs. Based on the Raman shift the size of the QD was estimated to be 4-6 nm. The volume fraction of Si crystals was calculated to be about 33%. The change of the FT-IR absorption spectrum from a Gaussian shape to a Lorentzian shape also confirmed the phase transition from an amorphous phase before annealing to a crystalline phase after annealing. The optical absorption coefficient also decreased, but the optical band gap increased from 1.5 eV to 2.1 eV after annealing. Therefore, it is expected that the optical energy gap of the QDs can be controlled with growth and annealing conditions.

• Journal of the Korean earth science society
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• v.22 no.3
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• pp.208-222
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• 2001

Geochemical investigations on suspended amorphous iron oxide material from the Kwangyang gold mine and its surrounding area, Cheonnam, Korea have been carried out. The sediments samples were collected from 11 location along Kwangyang mine area and were air dried and sieved to -80 mesh. These samples consist mainly of iron, silicon and alumina. The Fe$_2$O$_3$ contents ranges from 17.9 wt.% to 72.3 wt.%. The content of Fe$_2$O$_3$ increase with decreasing Si, Al, Mg, Na, K, Mn, and Ti, whereas the contents of Te, Au, Ga, Bi, Cd, Hg, Sb, and Se increase in the amorphous stream sediments. Amorphous stream sediments have been severely enriched for As (up to 54.9 ppm), Bi (up to 3.77 ppm), Cd (up to 3.65 ppm), Hg (up to 64 ppm), Sb (up to 10.1 ppm), Cu (up to 37.1 ppm), Mo (up to 8.86 ppm), Pb (up to 9.45 ppm) and Zn (up to 29.7 ppm). At the upstream site, the Au content (up to 4.4 ppm) in the amorphous stream sediments are relatively high but those contents decrease with distance of mine location. The content of Ag (up to 0.24 ppm) were low in upstream site but those contents increase significantly in the downstream sites. The X-ray diffraction patterns of the samples have virtually no sharp and discrete peaks, indicating that some samples are amorphous or poorly-ordered. The quartz, goethite, kaolinite and illite were associated in amorphous stream sediments. The infrared spectra for amorphous stream sediments show major absorption bands due to OH stretching, adsorbed molecular water, sulfate and Fe-O stretching, respectively.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.55-56
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• 1998

The 3-D Fast Gradient Echo (Turbo FLASH, Turbo Fast Low Angle Shot) sequence is optimized to achieve a good T1 contrast using variable excitation flip angles. In Turbo FLASH sequence, depending on the contrast preparation scheme, various types of image contrast can be established. While proton density contrast is obtained when using a short repetition time with a short echo time and small flip angles, T1 or T2 weighting can be obtained with proper contrast preparation sequences applied before the above proton density Turbo FLASH sequence. To maximize the contrast to noise ratio while retaining a sharp impulse response (smooth frequency domain response), the excitation flip-angle pattern is optimized through simulation and experiments. The TI (the delay after the preparation sequence which is a 180 degree inversion RF pulse in the IR T1 weighted imaging case), TD (the delay time between the Turbo FLASH sequence and the next preparation), and TR are also optimized fur the best image quality. The proposed 3-D Turbo FLASH provides $1mm\times1mm\times1.5mm$ high resolution images within a reasonable 5-8 minutes of imaging time. The proposed imaging sequence has been implemented in a Medison's Magnum 1.0T system and verified through simulations as well as human volunteer imaging. The experimental results show the utility of the proposed method.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.77-77
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• 2000

Titanium oxide (TiO2) thin films have valuable properties such as a high refractive index, excellent transmittance in the visible and near-IR frequency, and high chemical stability. Therefore it is extensively used in anti-reflection coating, sensor, and photocatalysis as electrical and optical applications. Specially, TiO2 have a high dielectric constant of 180 along the c axis and 90 along the a axis, so it is highlighted in fabricating dielectric capacitors in micro electronic devices. A variety of methods have been used to produce patterned self-assembled monolayers (SAMs), including microcontact printing ($\mu$CP), UV-photolithotgraphy, e-beam lithography, scanned-probe based micro-machining, and atom-lithography. Above all, thin film fabrication on $\mu$CP modified surface is a potentially low-cost, high-throughput method, because it does not require expensive photolithographic equipment, and it produce micrometer scale patterns in thin film materials. The patterned SAMs were used as thin resists, to transfer patterns onto thin films either by chemical etching or by selective deposition. In this study, we deposited TiO2 thin films on Si (1000 substrateds using titanium (IV) isopropoxide ([Ti(O(C3H7)4)] ; TIP as a single molecular precursor at deposition temperature in the range of 300-$700^{\circ}C$ without any carrier and bubbler gas. Crack-free, highly oriented TiO2 polycrystalline thin films with anatase phase and stoichimetric ratio of Ti and O were successfully deposited on Si(100) at temperature as low as 50$0^{\circ}C$. XRD and TED data showed that below 50$0^{\circ}C$, the TiO2 thin films were dominantly grown on Si(100) surfaces in the [211] direction, whereas with increasing the deposition temperature to $700^{\circ}C$, the main films growth direction was changed to be [200]. Two distinct growth behaviors were observed from the Arhenius plots. In addition to deposition of THe TiO2 thin films on Si(100) substrates, patterning of TiO2 thin films was also performed at grown temperature in the range of 300-50$0^{\circ}C$ by MOCVD onto the Si(100) substrates of which surface was modified by organic thin film template. The organic thin film of SAm is obtained by the $\mu$CP method. Alpha-step profile and optical microscope images showed that the boundaries between SAMs areas and selectively deposited TiO2 thin film areas are very definite and sharp. Capacitance - Voltage measurements made on TiO2 films gave a dielectric constant of 29, suggesting a possibility of electronic material applications.

• The Korean Journal of Nuclear Medicine Technology
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• v.28 no.1
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• pp.71-79
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• 2024

Purpose: This study aims to identify SUV, SNR, spatial resolution, and axial uniformity under the same reconstruction conditions and to find out the differences between equipment models. Materials and Methods: The equipment was GE's Discovery 600, 710, IQ, MI(GE Healthcare, USA), and the Phantom used ACR(American College of Radiology) Flangeless Esser Phantom and PET/SPECT Performance Phantom. The PET/SPECT Performance Phantom injected 18F-FDG at a concentration of 3.8 kBq/mL, and the ACR Flangeless Esser Phantom made the conditions for Hot Spot and Background activity for 4 : 1. Image evaluation was compared and evaluated for SUV, SNR, spatial resolution, and axial uniformity with the same reconstruction that added SharpIR of VPHD. Results: The SUV_max showed a difference up to 4.6% with an average of 2.71, 2.35, 1.89, and 1.43 from Hot Spot 1 to 4, and the SUV_mean showed a difference up to 4.7% with 2.06, 1.75, 1.49, and 1.27. There was a difference up to 5% between equipment, and there was no significant difference between both SUV_max and SUV_mean. SNR showed a difference up to 0.04 with an average of 0.37, 0.26, 0.18, and 0.11. FWHM showed a difference up to 0.27. Lastly, COV of axial uniformity was up to 0.018. Conclusion: SUV showed differences within 5% between equipment and showed no significant difference. This is considered to be used as basic data that can be used for the development and replacement of equipment because it has the advantage of being able to observe with a large number of equipment.

• Journal of Sericultural and Entomological Science
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• v.16 no.1
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• pp.21-48
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• 1974

The studies were carried out to disclose the physical and chemical properties of sericin fraction obtained from silk cocoon shells and its characteristics of swelling and solubility. The following results were obtained. 1. The physical and chemical properties of sericin fraction. 1) In contrast to the easy water soluble sericin, the hard soluble sericin contains fewer amino acids include of polar side radical while the hard soluble amino acid sach as alanine and leucine were detected. 2) The easy soluble amino acids were found mainly on the outer part of the fibroin, but the hard soluble amino acids were located in the near parts to the fibroin. 3) The swelling and solubility of the sericin could be hardly assayed by the analysis of the amino acid composition, and could be considered to tee closely related to the compound of the sericin crystal and secondary structure. 4) The X-ray patterns of the cocoon filament were ring shape, but they disappeared by the degumming treatment. 5) The sericin of tussah silkworm (A. pernyi), showed stronger circular patterns in the meridian than the regular silkworm (Bombyx mori). 6) There was no pattern difference between Fraction A and B. 7) X-ray diffraction patterns of the Sericin 1, ll and 111 were similar except interference of 8.85A (side chain spacing). 8) The amino acids above 150 in molecular weight such as Cys. Tyr. Phe. His. and Arg. were not found quantitatively by the 60 minutes-hydrolysis (6N-HCI). 9) The X-ray Pattern of 4.6A had a tendency to disappear with hot-water, ether, and alcohol treatment. 10) The partial hydrolysis of sericin showed a cirucular interference (2A) on the meridian. 11) The sericin pellet after hydrolysis was considered to be peptides composed with specific amino acids. 12) The decomposing temperature of Sericin 111 was higher than that of Sericin I and II. 13) Thermogram of the inner portioned sericin of the cocoon shell had double endothermic peaks at 165$^{\circ}C$, and 245$^{\circ}C$, and its decomposing temperature was higher than that of other portioned sericin. 14) The infrared spectroscopic properties among sericin I, II, III and sericin extracted from each layer portion of the cocoon shell were similar. II. The characteristics of seriein swelling and solubility related with silk processing. 1) Fifteen minutes was required to dehydrate the free moisture of cocoon shells with centrifugal force controlled at 13${\times}$10$^4$ dyne/g at 3,000 R.P.M. B) It took 30 minutes for the sericin to show positive reaction with the Folin-Ciocaltue reagent at room temperature. 3) The measurable wave length of the visible radiation was 500-750m${\mu}$, and the highest absorbance was observed at the wave length of 650m${\mu}$. 4) The colorimetric analysis should be conducted at 650mu for low concentration (10$\mu\textrm{g}$/$m\ell$), and at 500m${\mu}$ for the higher concentration to obtain an exact analysis. 5) The absorbing curves of sericin and egg albumin at different wave lengths were similar, but the absorbance of the former was slightly higher than that of the latter. 6) The quantity of the sericin measured by the colorimetric analysis, turned out to be less than by the Kjeldahl method. 7) Both temperature and duration in the cocoon cooking process has much effect on the swelling and solubility of the cocoon shells, but the temperature was more influential than the duration of the treatment. 8) The factorial relation between the temperature and the duration of treatment of the cocoon cooking to check for siricin swelling and solubility showed that the treatment duration should be gradually increased to reach optimum swelling and solubility of sericin with low temperature(70$^{\circ}C$) . High temperature, however, showed more sharp increase. 9) The more increased temperature in the drying of fresh cocoons, the less the sericin swelling and solubility were obtained. 10) In a specific cooking duration, the heavier the cocoon shell is, the less the swelling and solubility were obtained. 11) It was considered that there are differences in swelling or solubility between the filaments of each cocoon layer. 12) Sericin swelling or solubility in the cocoon filament was decreased by the wax extraction.. 13) The ionic surface active agent accelerated the swelling and solubility of the sericin at the range of pH 6-7. 14) In the same conditions as above, the cation agent was absorbed into the sericin. 15) In case of the increase of Ca ang Mg in the reeling water, its pH value drifted toward the acidity. 16) A buffering action was observed between the sericin and the water hardness constituents in the reeling water. 17) The effect of calcium on the swelling and solubility of the sericin was more moderate than that of magnecium. 18) The solute of the water hardness constituents increased the electric conductivity in the reeling water.