• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2006년도 춘계학술발표논문집
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• pp.298-301
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• 2006

DC-Motor is needed more and more sophisticated control to follow the highest precision of industrial automation and used in a number of control equipment or industrial fields. It is also useful to control single crystal($Al_2O_3$) growth. It is possible to procure a quality crystal utilizing a DC-Motor, if you mix Hydrogen and Oxygen gas properly and keep proper temperature in accordance with time process. In this paper, we will study about electrical valve positioning system for the gas mixture to improve the quality of single crystal($Al_2O_3$) growth and we will design about realtime monitoring systems of the automatic gas contol DC- Motor for single crystal($Al_2O_3$) growth

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.251-254
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• 1999

A new multi-seeding process for the growth of YBa$_2$Cu$_3$Oxx single crystals was developed. This process introduces an additional heating step to peritectic temperature and a subsequent slow cooling step to the growth temperature following the point when the crystals contacted. The crystal growth was resumed thereafter. The results obtained with this new process were compared with those of the conventional growth process, in which materials were only kept at the growth temperature. It was observed that the liquid phase between crystals were almost completely eliminated, but that Y2ll grains were grown during this new process. There was no significant improvement in trapped magnetic field over the conventional process, which is believed to be due to the cracks generated during the oxygen heat treatment or to the growth of YBa$_2$Cu$_3$Ox grains.

• 대한기계학회논문집
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• 제19권5호
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• pp.1308-1318
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• 1995

The influence of varying rotation speed of both crystal and crucible was numerically investigated for the Czochralski silicon-crystal growth. Based on a simplified model assuming flatness of free surfrae, the Navier-Stokes Boussinesq equations were employed to identify the flow pattern, temperature distribution as well as the shape of the melt/crystal interface. The present results showed that the interface shape was relatively convex with respect to the melt at lower pulling rate and tended to be concave as the pulling rate increased. In particular, the experimentally observed gull-winged shape of the interface was qualitatively in agreement with the predicted shape. The rotation of crystal alone little affected the growth system. When the rotation speed of the crucible was increased, there occurred inversion of the interface shape from convex to concave pattern. At rapid rotation of the crucible, an interesting channel formation was predictied primarily due to the assumption of laminar flow.

• 한국결정성장학회지
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• 제15권4호
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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.

• 한국결정성장학회지
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• 제11권4호
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• pp.180-183
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• 2001

Developed Edge-defined film-fed growth (EFG)법으로 $YVO_{4}$ 및 Nd:$YVO_{4}$ 단결정을 성장하였으며 성장된 결정의 광학적 특성을 측정하였다. $YVO_{4}$ 및 Nd:$YVO_{4}$ 단결정 모두 투명하였으며, 결정성장 동안 융액 표면 온도의 균질 및 meniscus의 안정화로 고품질의 결정을 얻을 수 있었다. 투과 및 흡수 스펙트럼 측정 결과에서 $YVO_{4}$ 단결정은 340 nm에서 1000 nm까지 대체로 넓은 영역에서 높은 투과율이 나타났지만, Nd:$YVO_{4}$ 단결정은 532, 593, 753, 807, 888 nm의 특정한 영역에서 흡수 peak들이 나타남을 획인할 수 있었다. 또한 Photoluminescence (PL) 스펙트럼을 측정한 결과, 800~900 nm의 영역에서 에너지 방출을 관찰할 수 있었다.

• 한국결정성장학회지
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• 제34권1호
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• pp.36-39
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• 2024

최근 전력반도체에 대한 관심이 확대되고 있는 가운데, SiC와 GaN 등의 광에너지갭 소재에 의한 소자화 및 응용에 대한 연구가 수행되고 있다. AlN 단결정은 이들 보다 더 큰 에너지갭을 갖기 때문에 대전력 소자화에 대한 연구도 진행중에 있으나, 상용화된 웨이퍼는 아직 보고되고 있지 않아 이에 대한 연구가 필요하다. 본 연구에서는 AlN 단결정을 제조하기 위하여 HVPE(Hydride vapor phase epitaxy) 법을 적용하였고, 자체 제작 설비를 이용하여, 벌크 단결정을 얻어내고자 하였으며, 이를 위해 단결정의 성장 조건을 확보하고자 한 결과를 보고하고자 하며, 온도의 변화에 따라 성장된 결정의 형상의 변화에 대하여 보고하고자 한다.

• 한국결정성장학회지
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• 제4권3호
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• pp.325-335
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• 1994

Floating zone법으로 Spinel$(MgO.Al_2O_3)$을 성장시켰다. $MgO.Al_20_3$ spinel의 용융점은 $2135^{\circ}C$ 정도이고, 용융액으로부터 단결정을 성장시키는 방법에 있어서 매우 중용한 사항이다. Verneuil법과 RF-유도가열법을 이용한 czochralski법으로 성장시킨 경우가 보고된 바 있으나, 본 공법으로는 처음이라 사료된다. 본 연구에서는 halogen적외선 lamp를 이용한 image fur-nace에서 용융하여 아래쪽으로 하강함으로 인해 단결정을 육성시키는 floating zone법을 사용하여, $MgAl_2O_4$ spinel 단결정을 성장하였다. 또한 전이금속 이온을 doping하여 용융점의 하강 효과와 함께 적색, 녹색을 띈 단결정을 성장시켰다. 결론으로 성장계면과 용융대의 안전성에 주목하여 spinel 단결정 성장 기구를 규명하려 하였으며 성장계면이 오목함(결정쪽으로)에서 비롯되는 성장시의 양상에 대해 고찰하였다.

• 한국결정성장학회지
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• 제6권1호
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• pp.44-55
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• 1996

천연 베릴을 이용하여 $V_20_5$, $Mo0_3$, $Li_2O$계 융제 및 첨가제 조성, 베렬의 용해도 그 리고 결정성장 온도와 같은 결정성창 조건을 제어하여 에메랄드 단결정을 성장시켰다. Flux와 첨가제를 조정하여 저온($1100^{\circ}C$ 이하)에셔 용해성이 높은 과포화 용융체를 만들고 온도 구배 (${\Delta}t 100^{\circ}C$), 열진동 효과 등을 정멀 제어 조정하므로써 고품질의 대형 emerald 단결정을 성장 시킬 수 있었다. 성장된 에메랄드 단결정의 특성은 굴절률 : 1.56 - 1.57, 비중 : 2.65 - 2.67인 6각 주상($c^*m$ : 1000, 1010)의 취록색 투명 단결정이였다.

• 한국전기전자재료학회논문지
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• 제21권9호
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• pp.795-800
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• 2008

A sublimation method using the SiC seed crystal and SiC powder as the source material is commonly adopted to grow SiC bulk single crystal. However, it has proved to be difficult to achieve the high quality crystal and the process reliability because SiC single crystal should be grown at very high temperature in closed system. The present research was focused to improve SiC crystal quality grown by PVT method through using the new inner guide tube. The new inner guide tube was designed to prevent the enlargement of polycrystalline region into single crystalline region and to enlarge the diameter of SiC single crystal. The 6H-SiC crystals were grown by conventional PVT process. The seed adhered on seed holder and the high purity SiC source materials are placed on opposite side in sealed graphite crucible surrounded by graphite insulation. The SiC bulk growth was conducted around 2300 $^{\circ}C$ of growth temperature and 50 mbar in an argon atmosphere of growth pressure. The axial thermal gradient across the SiC crystal during the growth was estimated in the range of 15${\sim}$20 $^{\circ}C$/cm.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.112-113
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• 2006

A stoichiometric mixture for $Cdln_2Te_4$ single crystal was prepared from horizontal electric furnace. The $Cdln_2Te_4$ single crystal was grown in the three-stage vertical electric furnace by using Bridgman method. The quality of the grown crystal has been investigated by the x-ray diffraction and the photoluminescence measurements. The (001) growth plane of oriented $Cdln_2Te_4$ single crystal was confirmed from back-reflection Laue patterns. The carrier density and mobility of $Cdln_2Te_4$ single crystal measured with Hall effect by van der Pauw method are $8.61{\times}10^{16}\;cm^{-3}$ and $242\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $Cdln_2Te_4$ single crystal obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;1.4750\;eV\;-\;(7.69{\times}\;10^{-3}\;eV)T^2/(T+2147)$.