• Macromolecular Research
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• v.12 no.2
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• pp.189-194
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• 2004

When water is evaporated quickly from a water-based colloidal suspension, colloidal particles protrude from the water surface, distorting it and generating lateral capillary forces between the colloidal particles. The protruded colloidal particles are then assembled into ordered colloidal crystalline domains that float on the water surface on account of their having a lower effective density than water. These colloidal crystal domains then assemble together by lateral capillary force and convective flow; the generated colloidal crystal has grain boundaries. The single domain size of the colloidal crystal could be controlled, to some extent, by changing the rate of water evaporation, but it seems very difficult to fabricate a single crystal over a large area of the water's surface without reorienting each colloidal crystal domain. To reorient such colloidal crystal domains, a glass plate was dipped into the colloidal suspension at a tilted angle because the meniscus (airwaterglass plate interface) is pinned and thinned by further water evaporation. The thinning meniscus generated a shear force and reoriented the colloidal crystalline domains into a single domain.

• Journal of Korean Port Research
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• v.12 no.2
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• pp.323-328
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• 1998

A quartz crystal analyzer is utilized to monitor the corrosion process of an aluminum surface of a quartz crystal for marine sensor by sea water. A quartz crystal having 2000 $\AA$ of aluminum layer is installed in a specially designed cell and is in contact with sea water imitated electrolyte solution. While a constant potential is applied to the cell, the resonant frequency and resonant resistance are simultaneously measured using the quartz crystal analyzer. In addition, surface topographs are taken with an atomic force microscope(AFM) and the element analysis of the surface is conducted using an energy dispersive X-ray spectrometer(EDX). The simultaneous measurement of resonant frequency and resonant resistance during the corrosion process explains the change of surface structure caused by the corrosion. The variation of resonant frequency addresses the amount surface metal dissolution. As a conclusion, it is found that a simple measurement using the quartz crystal analyzer can replace the complex monitoring employing large equipments in the investigation of a corrosion process of sensor surface.

• Current Photovoltaic Research
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• v.5 no.2
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• pp.43-46
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• 2017

Large absorption band shift has been observed for the azo-dye (disperse red-13, DR-13) attached on the surface of silica spheres. Urethane linkage has been utilized to form covalent bond between azo-dye (-OH) and 3-isocyanatopropyltriethoxysilane (ICPTES, -N=C=O). The synthesized ICPTES-DR-13 (ICPDR) molecules were attached to the silica spheres by the hydrolysis and condensation reaction. Although the absorption peak of DR-13 in methanol is at 510 nm, the absorption peak of the ICPDR-silica spheres shifts to 788 nm. The large absorption peak shift is due to the formation of intramolecular charge-transfer band with large aggregated ICPDR.

• Current Photovoltaic Research
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• v.1 no.2
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• pp.103-108
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• 2013

Epitaxial growth of a high-quality thin Si film is essential for the application to low-cost thin-film Si solar cells. A polycrystalline Si film was grown on a $SiO_2$ substrate at $450^{\circ}C$ by a Al-assisted crystal growth process. For the purpose, a thin Al layer was deposited on the $SiO_2$ substrate for Al-assisted crystal growth. However, the epitaxial growth of Si film resulted in a rough surface with humps. Then, we introduced a thin amorphous Si seed layer on the Al film to minimize the initial roughness of Si film. With the help of the Si seed layer, the surface of the epitaxial Si film was smooth and the crystallinity of the Si film was much improved. The grain size of the $1.5-{\mu}m$-thick Si film was as large as 1 mm. The Al content in the Si film was 3.7% and the hole concentration was estimated to be $3{\times}10^{17}/cm^3$, which was one order of magnitude higher than desirable value for Si base layer. The results suggest that Al-doped Si layer could be use as a seed layer for additional epitaxial growth of intrinsic or boron-doped Si layer because the Al-doped Si layer has large grains.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.5-14
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• 2003

Principles of a novel pulse growing method are described. The method realized in the crystal growing on a seed from melts under raw melt feeding provided a more reliable control of the crystallization process when producing large alkali halide crystals. The slow natural convection of the melt in the crucible at a constant melt level is intensified by rotating the crucible, while the crystal rotation favors a more symmetrical distribution of thermal stresses over the crystal cross-section. Optimum rotation parameters for the crucible and crystal have been determined. The spatial position oi the solid/liquid phase interface relatively to the melt surface, heaters and the crucible elements are considered. Basing on that consideration, a novel criterion is stated, that is, the immersion extent of the crystallization front (CF) convex toward the melt. When the crystal grows at a <> CF immersion, the raised CF may tear off from the melt partially or completely due to its weight. This results in avoid formation in the crystal. Experimental data on the radial crystal growth speed are discussed. This speed defines the formation of a gas phase layer at the crystal surface. The layer thickness il a function of time a temperature at specific values of pressure in the furnace and the free melt surface dimensions in the gap between the crystal and crucible wall. Analytical expressions have been derived for the impurity component mass transfer at the steady-state growth stage describing two independent processes, the impurity mass transfer along the <> path and its transit along the <> one. The heater (and thus the melt) temperature variation is inherent in any control system. It has been shown that when random temperature changes occur causing its lowering at a rate exceeding $0.5^{\circ}C/min$, a kind of the CF decoration by foreign impurities or by gas bubbles takes place. Short-term temperature changes at one heater or both result in local (i.e., at the front) redistribution of the preset axial growth speed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.74-81
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• 1991

The temperature profile of Czochralski single crystal growth system was simulated considering the fluid flow and surface radiation heat transfer. View factors of surface elements were calculated for radiation heat transfer. Two phases(solid and liquid) were treated as a continuous phase by assigning artificial large viscosity to the solid phase and latent heat was accounted by iterative heat revolution method. The solidification model was applied to solid front of the pure Ga during the melting to verify the model. The whole simulation model of CZ system was applied to the growth Al single crystal.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.4
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• pp.141-144
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• 2005

[ $(Y_{0.5}Sm_{0.25}Nd_{0.25})Ba_2Cu_3O_y$ ] [(YSN)-123] high $T_c$ composite superconductors with $CeO_2$ addition were systematically investigated by top seeded melt growth (TSMG) process in air atmosphere. A melt textured $NdBa_2Cu_3O_y$ (Nd-123) single crystal was used as a seed for achieving the c-axis alignment large grains perpendicular to the surface of (YSN)-123 composite oxides. The size of $(Y_{0.5}Sm_{0.25}Nd_{0.25})_2BaCuO_5$ [(YSN)211] nonsuperconducting inclusions of the melt textured (YSN)-123 samples with $CeO_2$ addition were remarkably reduced and uniformly distributed within the (YSN)123 superconducting matrix except in the region very close to the Nd-123 seed crystal. The sample showed a sharp superconducting transition of 91 K.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.3
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• pp.140-142
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• 2019

AlN (Aluminum Nitride) crystal which could be used to substrates for UV LEDs was grown by PVT ((Physical Vapor Transport) method. 3 inch AlN single crystal with a thickenss of 4 mm was grown using Polycrystalline seed for 120 hours. In this report, a result of 3 inch polycrystalline bulk AlN growth behavior using large size crucible and growth condition were reported.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.768-773
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• 2005

We present an overview of our new method of liquid crystal (LC) alignment based on the anisotropic etching of the alignment layers with a directed plasma flux. The method is realized by the use of anode layer source of "race track" geometry generating two "sheets" of accelerated plasma. These sheets are directed obliquely to the treated substrates. The static and dynamic irradiation regimes have been explored. The optimized processing conditions and materials are discussed. The technique yields an excellent uniformity of liquid crystal alignment of planar, tilted and vertical types. It is shown that the new method can be easily adapted for the alignment treatment of large area substrates used in the modern LCD manufacturing process.

• Korean Journal of Crystallography
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• v.1 no.1
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• pp.8-13
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• 1990

Synthetic citrines were grown by hydrothermal method. For the establishment of grown conditions of large citrine, various types and/or amount of nutrients, seed orientations, mineralizers, colorants and temperature gradients were studied. For the evaluation of the quality of as grown citrine, color tone, crystal form, macro-and micro-defects were observed and crystal structure and absorption spectrums were analyzed. As a result, large sized citrines of 205mm L x 58mm W x 35mm T with excellent color tone and minium defects were grown.