• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.4
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• pp.170-174
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• 2018

AlN crystal is been developing in global site for many years and 1 inch diameter wafer was already developed but it is demanding the efforts for the better quality. On the other hand, also the 2-inch size is developing recently to reduce the unit cost for manufacturing and to use to fabrication of the UV LED chips. In this study, we tried to evaluate the possibility of bulk AlN crystals on his thin films by PVT method. The AlN thin film was grown on SiC single crystal 2" wafer by HVPE method. We successfully grew AlN bulk crystal of a thickness of 7 mm using its thin film of a thickness of $10{\mu}m$ as a seed crystal. The resultants of AlN crystals were identified by metallurgical microscope, optical stereographic microscope and DCXRD measurement.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.1-5
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• 1997

The $Bi_2Sr_2Ca_{n-1}Cu_nOy$(BSCCO) phase is well known to be a superconductor having a strong anisotropic behavior. It can be seen that it is difficult to control the growth direction. In this study, we try to grow a Bi-Sr-Ca-Cu-O phase crystal by the crystal pulling method with a seed crystal and crucibel rotation. Relatively large crystals of the order of $5{\times}5{\times}5{\textrm}{mm}^3$ dimensions can be obtained. We also discuss the possible crystallization field of the $BiO_{1.5}$-(Sr, Ca)O-CuO ternary phase diagram, and present some results of the characterization and magnetic measurements on the grown crystal.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.1-9
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• 1998

In this study, we have investigated the preparation conditions of 45$\times$45$\times$20(mm) square cross-section sapphire single crystal by the modified heat exchanger method using water as a coolant. Melting and solidification processes were optimized by the systematic change of the chamber pressure with the heater temperature. As a results, solidification temperature was between 1960 and $1970^{\circ}C$. The crucible was formed by handling. Therefore its shape should had the 'spiral type' ear at edge of its side. Heat exchanger affected to the temperature distribution and gradient of molten alumina. Heat flux and unmelted seed were controlled by volume of heat exchanger. Voids were controlled by the cooling rate of the heater below $0.2^{\circ}C$/min.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.242-245
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• 2009

AlN crystals were grown by a sublimation process without seed crystals and the growth morphology of them was characterized. The grown AlN crystals were a polycrystalline phase, which had a diameter of $60\sim200\;{\mu}m$ and were grown with a growth rate of $0.2\sim0.5\;{\mu}n/hr$. It was observed that the as-grown crystals had a hexagonal crystal structure and revealed that these crystals were grown with a morphology of columnar morphology in the initial stage of the growth before they were enlarged in a way of a lateral growth behavior in the final stage. On the surface, a lot of pinholes were observed on the surface of crystals grown. The evolution of a growth morphology was characterized by optical and scanning electron microscopic observation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.49-53
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• 1997

In this paper, YbBa$_{2}$Cu$_{3}$O$_{x}$ superconductor was sintered by means of conventional solid reaction and the textured YbBa$_{2}$Cu$_{3}$O$_{x}$ was prepared by the Melted-Condensed Process in which SmBa$_{2}$Cu$_{3}$O$_{x}$ crystal was used as seed crystal to introduce the YbBa$_{2}$Cu$_{3}$O$_{x}$ crystal growth. The texture of YbBa$_{2}$Cu$_{3}$O$_{x}$ was examined by X-ray diffraction, and the fracture of YbBa$_{2}$Cu$_{3}$O$_{x}$ sample was observed by SEM, which proved the sample was well oriented. After oxygen absorption of the textured YbBa$_{2}$Cu$_{3}$O$_{x}$ sample, it's critical temperature was measureed to be 86K.eed to be 86K.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.90-96
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• 1994

In this paper, an experiment about the fabrication method of superconductor was made in order to obtain crystal structure by making High T$\sub$C/, superconductor Y$_1$Ba$_2$Cu$_3$O$\sub$x/ to Y$_2$Ba$_1$Cu$_1$O$\sub$x/ of nonsuperconductor phase was added. 211 phase, which can approach crystal structure and growth-orientatoun, was used as seed in the 123 phase which shows the properties of superconductor. Therefore crystal growth effect was able to be attained. And the effect is expected to eleminate thin crack in the growth-process and to improve electrical properties by adding Ag to High T$\sub$c/ superconductor Y$_1$Ba$_2$Cu$_3$O$\sub$x/ combined with Y$_2$Ba$_1$Cu$_1$O$\sub$x/ .

• 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.

• Korean Chemical Engineering Research
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• v.58 no.3
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• pp.369-380
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• 2020

Most mono-crystalline silicon ingots are manufactured by the Czochralski (Cz) process. But If there are oxygen impurities, These Si-ingot tends to show low-efficiency when it is processed to be solar cell substrate. For making single-crystal Si- ingot, We need Czochralski (Cz) process which melts molten Si and then crystallizing it with seed of single-crystal Si. For melts poly Si-chunk and forming of single-crystalline Si-ingot, the heat transfer plays a main role in the structure of Cz-process. In this study to obtain high-quality Si ingot, the Cz-process was modified with the process design. The crystal growth simulation was employed with pulling rate and rotation speed optimization. Studies for modified Cz-process and the corresponding results have been discussed. The results revealed that using crystal growth simulation, we optimized the oxygen concentration of single crystal silicon by the optimal design of the pulling rate, rotation speed and melt charge level of Cz-process.

• Restorative Dentistry and Endodontics
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• v.37 no.1
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• pp.16-23
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• 2012

Objectives: Present study was undertaken to investigate the crystal growth onto synthetic hydroxyapatite (HA) seeds in pH 4.3 and pH 7.0 supersaturated solutions with different fluoride concentrations. Materials and Methods: 8 groups of pH 4.3 and 7.0 calcium phosphate supersaturated solutions were prepared with different fluoride concentrations (0, 1, 2 and 4 ppm). Calcium phosphate precipitates yield crystal growth onto the HA seed surface while solutions flow. For evaluation of crystallizing process, the changes of $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ concentrations of the inlet and outlet solutions were determined. The recovered solid samples were weighed to assess the amount of minerals precipitated, and finally determined their composition to deduce characteristics of crystals. Results: During the seeded crystal growth, there were significantly more consumption of $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ in pH 4.3 solutions than pH 7.0 (p < 0.05). As fluoride concentration increased in pH 4.3 solution, $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ consumption in experimental solutions, weight increment of HA seed, and fluoride ratio in crystallized samples were increased. There were significant differences among the groups (p < 0.05). But in pH 7.0 solution, these phenomena were not significant. In pH 7.0 solutions, analyses of crystallized samples showed higher Ca/P ratio in higher fluoride concentration. There were significant differences among the groups (p < 0.05). But in pH 4.3 solution, there were not significant differences in Ca/P ratio. Conclusions: Crystal growth in pH 4.3 solutions was superior to that in pH 7.0 solutions. In pH 4.3 solutions, crystal growth increased with showed in higher fluoride concentration up to 4 ppm.

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.438-442
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• 1997

In this study we report the effect of melt instability on the Liquid Phase Epitaxy. We made a new graphite boat of the structure relieving the instability of melt. It did not improve the uniformity of each layers but also reduced the thickness of growth layers and the deviation of the thickness over 1/2, 1/3 respectively. Moreover, we could get the growth layer of about 80$\AA$. With the point of melt stability in view we investigated the effect of InP seed used in two phase solution method. It is concluded that the quality of layers grown by the single crystal is superior to that by the poly crystal in two phase solution method.