• Journal of the Korean Ceramic Society
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• v.56 no.6
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• pp.589-595
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• 2019

The top-seeded solution growth (TSSG) method is an effective approach for the growth of high-quality SiC single crystals. In this method, the temperature gradient in the melt is the key factor determining the crystal growth rate and crystal quality. In this study, the effects of the aperture at the top of the hot-zone on the growth of the SiC single crystal obtained using the TSSG method were evaluated using multiphysics simulations. The temperature distribution and C concentration profile in the Si melt were taken into consideration. The simulation results showed that the adjustment of the aperture at the top of the hot-zone and the temperature gradient in the melt could be finely controlled. The surface morphology, crystal quality, and polytype stability of the grown SiC crystals were investigated using optical microscopy, high-resolution X-ray diffraction, and micro-Raman spectroscopy, respectively. The simulation and experimental results suggested that a small temperature gradient at the crystal-melt interface is suitable for growing high-quality SiC single crystals via the TSSG method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.113-114
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• 2009

Silicon carbide is one of the most attractive and promising wide band-gap semiconductor material with excellent physical properties and huge potential for electronic applications. Up to now, the most successful method for growth of large SiC crystals with high quality is the physical vapor transport (PVT) method [1, 2]. Since further reduction of defect densities in larger crystal are needed for the true implementation of SiC devices, many researchers are focusing to improve the quality of SiC single crystal through the process modifications for SiC bulk growth or new material implementations [3, 4]. It is well known that for getting high quality SiC crystal, source materials with high purity must be used in PVT method. Among various source materials in PVT method, a SiC powder is considered to take an important role because it would influence on crystal quality of SiC crystal as well as optimum temperature of single crystal growth, the growth rate and doping characteristics. In reality, the effect of powder on SiC crystal could definitely exhibit the complicated correlation. Therefore, the present research was focused to investigate the quality difference of SiC crystal grown by conventional PVT method with using various SiC powders. As shown in Fig. 1, we used three SiC powders with different particles size. The 6H-SiC crystals were grown by conventional PVT process and the SiC seeds and the high purity SiC source materials are placed on opposite side in a sealed graphite crucible which is surrounded by graphite insulation[5, 6]. The bulk SiC crystal was grown at $2300^{\circ}C$ of the growth temperature and 50mbar of an argon pressure. The axial thermal gradient across the SiC crystal during the growth is estimated in the range of $15\sim20^{\circ}C/cm$. The chemical etch in molten KOH maintained at $450^{\circ}C$ for 10 min was used for defect observation with a polarizing microscope in Nomarski mode. Electrical properties of bulk SiC materials were measured by Hall effect using van der Pauw geometry and a UV/VIS spectrophotometer. Fig. 2 shows optical photographs of SiC crystal ingot grown by PVT method and Table 1 shows electrical properties of SiC crystals. The electrical properties as well as crystal quality of SiC crystals were systematically investigated.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.161-164
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• 1998

Erbium doped garnet crystals were grown by Czochralski method. Relationshipes between crystal quality and crystal growth factors such as pulling rate, rotation rate and concentration of active ions and sensitizers were investigated. Optimum pulling and rotation rate for high quality Er:YAG crystal were 1 mm/hr and 20 rpm and for Er,Cr:YSGG crystal 2-4 mm/hr and 10 rpm respectively. The size of the crystals grown was up to 20-30 mm in diameters and 95-135 mm in length. Er:YAG crystal grown under the nitrogen atmosphere was pink and transparent and Er,Cr:YSGG under the 98% {{{{ { N}_{ 2} }}}} and 2% {{{{ { O}_{2 } }}}} was dark green and transparent. Under the polarizing microscopic observations with crossed polar, striations and {211} core facets were detected. Spectroscopic properties for Er,Cr:YSGG laser rods with <111> axis, 80 mm in length and 6.3 mm in diameter for medical laser applications of 2.79 ${\mu}$m wavelength were manufactured and then laser oscillation was achieved.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.97-102
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• 1998

Transition metal Cr3+ and Fe3+ ion was diffused in white sapphire {0001}, {1010} crystal plane which were grown by the Verneuil method. It enhanced and changed the physical, electrical and optical properties of sapphires. After mixing the metallic oxide and metal powder, it were used for diffusion. Metallic oxide was synthesized by precipitation method and it's composition was mainly alumina which doped with chromium or ferric oxide. In case using metallic oxide, the dopping was slowly progressed and it needed the longer duration time and higher temperature, relatively. Metallic powder was vapoured under 1x10-4 torr of vacuum pressure at 1900(iron metal) and 2050(chromium)℃, first step. Diffusion condition were kept by 6atm of N2 accelerating pressure at 2050∼2150℃. Each surface density of sapphire crystal are 0.225(c) and 0.1199atom/Å2(a). The color of the Cr-doped sapphires was changed to red. Dopping reaction was come out more deep in th plane of {1010} than {0001}. It was speculated that the planar density was one of the factors to determine diffusion effect.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.91-95
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• 2000

The effects of argon gas flow on the axial temperature gradient near the interface, the oxygen concentration, and the radial oxygen uniformity was investigated for 8-inch CZ silicon growth. As argon flow rate was increased, the temperature gradient was increased in the crystal near the crystavmelt interface and the oxygen content in the crystal was decreased. But the radial oxygen uniformity was deteriorated. It was found that argon flow is one of the important growing parameters to affect the quality of crystals such as oxygen content and uniformity.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.29-33
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• 1998

Transport phenomena paly an inmportant role in bulk crystal growth processes. During crystal growth, the control of the growth front and the dopant concentration is crucial to crystal quality. The growth feasibility in thus determined by the heat transfer controlling the interface convexity and by the mass transfer controlling the constitutional supercooling. Through numerical modeling, a thorough understanding of the growth processes is possible, which in turn is a key to process improvenment. In this paper, we will summarize some work dine in my laboratory, both numerical and experimental, to illustrate the importance of understanding the transport phenomena during crystal growth processes.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.3
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• pp.119-123
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• 2013

Most of the world's solar cells in photovoltaic industry are currently fabricated using crystalline silicon. Czochralski-grown silicon crystals are more expensive than multicrystalline silicon crystals. The future of solar-grade Czochralski-grown silicon crystals crucially depends on whether it is usable for the mass-production of high-efficiency solar cells or not. It is generally believed that the main obstacle for making solar-grade Czochralski-grown silicon crystals a perfect high-efficiency solar cell material is presently light-induced degradation problem. In this work, the substitution of boron with gallium in p-type silicon single crystal is studied as an alternative to reduce the extent of lifetime degradation. The diamond-wire sawing technology is employed to slice the silicon ingot. In this paper, the quality of the diamond wire-sawn gallium-doped silicon wafers is studied from the chemical, electrical and structural points of view. It is found that the characteristic of gallium-doped silicon wafers including texturing behavior and surface metallic impurities are same as that of conventional boron-doped Czochralski crystals.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.305-320
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• 1999

It was grown Er2O3 doped LiNbO3 single crystal thin films with high crystal quality by liquid phase epitaxial (LPE) method. Er2O3 was doped with a concentration of 1, 3, and 5 mol% respectively. After the growth of single crystal thin film, we examined the crystallinity and the lattice mismatch along the c-axis between the film and the substrate with the variation of Er2O3 dopant using X-ray double crystal technique. There were no lattice mismatches along the c-axis for the undoped and the films doped with 1 and 3 mol% of Er2O3. For 5 mol% of Er2O3 doped film, there was a lattice mismatch of 7.86x10-4nm along the c-axis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.295-298
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• 1999

High quality of $Er_{2}O_{3}$ doped $LiNbO_{3}$ single crystal thin films were grown by the liquid phase epitaxial (LPE) method using $Er_{2}O_{3}$ doped at concentrations of 1,3, and 5 mol% respectively. After the growth of single crystal thin film, the crystallinity and the lattice mismatch along the c-axis between the film and the substrate was examined as a function of the variations of{{{{{Er}_{2}{O}_{3}}}}} dopant concentration using a X-ray double crystal technique. There was no lattice mismatch along the c-axis for the undoped film and those doped with 1 and 3 mol% of $Er_{2}O_{3}$. For 5 mol% of $Er_{2}O_{3}$ doped film, the lattice mismatch was $7.86{\times}10^{-4}$nm along the c-axis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.263-268
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• 1998

(100) ZnSe crystals with twin and grain free were grown by vapor transport method. The defect in (100) ZnSe crystals was investigated by FWHM of X-ray Rocking Curve. The growth rate and seed quality are the main parameters of the growth process to obtain the high quality ZnSe crystals. The geometric shape of the grown (100) ZnSe crystal is dependent on the shape of seed, isothermal line in furnace and the growth rate of each surface in crystal.