• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.232-232
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• 2006

SiC single crystal Ingots were prepared onto different seed material using sublimation PVT techniques and then their crystal quality was systematically compared. In this study, the conventional SiC seed material and the new SiC seed material with an inserted SiC epitaxial layer on a seed surface were used as a seed for SiC bulk growth. The inserted epitaxial layer was grown by a sublimation epitaxy method called the CST with a low growth rate of $2{\mu}m/h$ N-type 2"-SIC single crystals exhibiting the polytype of 6H-SiC were successfully fabricated and carrier concentration levels of below $10^{17}/cm^3$ were determined from the absorption spectrum and Hall measurements. The slightly higher growth rate and carrier concentration were obtained in SiC single crystal Ingot grown on new SiC Seed materials with the inserted epitaxial layer on the seed surface, maintaining the high quality.

• 한국전기전자재료학회논문지
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• 제24권10호
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• pp.799-802
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• 2011

In this study, SiC single-crystal ingots were prepared on two seed crystals with different doping level by using the physical vapor transport (PVT) technique; then, SiC crystal wafers sliced from the grown SiC ingot were systematically investigated to find the effect of seed doping level on the doping concentration and crystal quality of the SiC. To exclude extra effects induced by adjustment of the process parameters, we simultaneously grew the SiC crystals on two seed crystals with different level, which were fabricated from previous two SiC crystal ingots.

• 소성∙가공
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• 제14권6호
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• pp.502-508
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• 2005

Hypereutectic Al-Si alloys have been regarded attractive for automotive and aerospace application, due to high specific strength, good wear resistance, high thermal stability, low thermal expansion coefficient and good creep resistance. Spray casting of hypereutectic Al-Si alloy has been reported to provide distinct advantages over ingot metallurgy (IM) or rapid solidification/powder metallurgy (RS/PM) process in terms of microstructure refinement. In this study, hypereutectic Al-25Si-2.0Cu-1.0Mg alloy was prepared by OSPREY spray casting process. The change of strain rate sensitivity and Creep transition were analyzed by using the load relaxation test and constant creep test. High temperature deformation behavior of the hypereutectic Al-Si alloy has been investigated by applying the internal variable theory proposed by Chang et al. Especially, the creep resistance of spray casted hypereutectic Al-Si alloy can be enhanced considerably by the accumulation of prestrain.

• 한국결정성장학회지
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• 제24권2호
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• pp.47-53
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• 2014

태양전지용 규소에는 단결정, 다결정, mono-like의 세 가지 재료가 사용 중에 있다. 첫 번째로, 단결정은 수율향상의 과제에 집중되고 있으며, 이것은 고액 계면의 형상이 주요 요인으로 알려지고 있다. 이에 대한 연구가 전산모사 등으로 집중되고 있다. 또한 결정과 도가니의 회전 속도가 고액 계면의 형상에 영향을 미치는 것이 확인 되었다. 다결정의 경우에는 결정립계의 역할이 매우 중요하므로 이에 대한 연구가 진행되는데, 이들을 특히 전기적으로 비활성적인 쌍정 입계로 전환하는 연구가 진행되고 있다. 성장 조건을 변경시켜 쌍정 입계로 바꾸어서 재료의 전기적 성질을 향상시키는 결과를 확인하였다. 또한 성장 공정에서 발생될 수 있는 오염을 줄이기 위한 노력은 상부의 Ar 가스의 흐름을 상향 조절하여 불순물의 용입을 줄임이 확인되었다. 다음으로 mono-like인 경우에는 측면으로부터 성장 되어 들어오는 다결정이 단결정의 분율을 저하 시키는 주요 요인이 되고 있다. 이에 대한 해결책으로 하부의 냉각 속도를 높이고 상부와 측면에 단열재를 보강하는 방안이 제시되고 있고, 하부에 놓는 seed의 orientation을 조절하여 측면으로부터 성장 되어 들어오는 다결정을 억제하는 방안이 효과가 있음이 확인 되고 있다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.111.1-111.1
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• 2011

The solar energy is dramatically increasing as the alternative energy source and the silicon(Si) solar cell are used the most. In this study, the improved process and equipment for the metallurgical refinement of multicrystalline Si were evaluated for the inexpensive solar cell. The planar plane and columnar dendrite aheadof the liquid-solid interface position caused the superior segregation of impurities from the Si. The solidification rate and thermal gradient determined the shape of dendrite in solidified Si matrix solidified by the directional solidification(DS) method. To simulate this equipment, the commercial software, PROCAST, was used to solve the solidification rate and thermal gradient. Si was vertically solidified by the DS system with Stober process and up-graded metallurgical grade or metallurgical grade Si was used as the feedstock. The inductively coupled plasma mass spectrometry (ICP) was used to measure the concentration of impurities in the refined Si ingot. According to the result of ICP and simulation, the high thermal gradient between the two phases wasable to increase the solidification rate under the identical level of refinement. Also, the separating heating zone equipped with the melting and solidification zone was effective to maintain the high thermal gradient during the solidification.

• 한국주조공학회지
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• 제28권4호
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• pp.179-183
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• 2008

Mechanical properties of the spray-cast Al 6061 alloy with variation of Mg/Si addition were investigated. After spray-cast, hot extrusion was performed at $460^{\circ}C$ then followed ageing treatment to the T6 condition. SEM, EDX, and XRD were used to characterize a ${\beta}(Mg_{2}Si)$ precipitate. The amount of ${\beta}$ precipitate was calculated from the XRD measurements. Hardness, ultimate tensile strength and elongation were tested then compared with those of the Al 6061 alloys made by ingot metallurgy (I/M) and powder metallurgy (P/M). The ultimate tensile strength and elongation of the spray-cast Al 6061 alloy were 318MPa and 16.5%, respectively. These properties were improved in the 2.2 wt%Mg and 1.3wt%Si addition up to 349MPa of UTS and 12.5% of elongation, mainly due to increased amount of a fine supersaturated ${\beta}(Mg_{2}Si)$ precipitate.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.299.2-299.2
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• 2013

We investigated the potassium remaining on a crystalline silicon solar cell after potassium hydroxide (KOH) etching and its effect on the lifetime of the solar cell. KOH etching is generally used to remove the saw damage caused by cutting a Si ingot; it can also be used to etch the rear side of a textured crystalline silicon solar cell before atomic layer-deposited Al2O3 growth. However, the potassium remaining after KOH etching is known to be detrimental to the efficiency of Si solar cells. In this study, we etched a crystalline silicon solar cell in three ways in order to determine the effect of the potassium remnant on the efficiency of Si solar cells. After KOH etching, KOH and tetramethylammonium hydroxide (TMAH) were used to etch the rear side of a crystalline silicon solar cell. To passivate the rear side, an Al2O3 layer was deposited by atomic layer deposition (ALD). After ALD Al2O3 growth on the KOH-etched Si surface, we measured the lifetime of the solar cell by quasi steady-state photoconductance (QSSPC, Sinton WCT-120) to analyze how effectively the Al2O3 layer passivated the interface of the Al2O3 layer and the Si surface. Secondary ion mass spectroscopy (SIMS) was also used to measure how much potassium remained on the surface of the Si wafer and at the interface of the Al2O3 layer and the Si surface after KOH etching and wet cleaning.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 춘계학술발표회논문집(2)
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• pp.609-615
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• 1995

Chip machining에 의한 U$_3$Si 분말제조시 절삭가공조건이 분말 입도 분포에 미치는 영향을 조사하기 위하여 U$_3$Si ingot를 선반에서 초경공구를 사용하여 절삭속도 및 이송속도를 변화시키면서 chip을 가공하였고, 가공된 chip의 형상을 광학현미경으로 관찰하고 칩의 크기를 측정하였다. 모든 절삭조건에서 톱니모양의 칩(saw toothed chip)이 형성되었으며, 일정한 절삭속도에서 공구의 이송속도를 변화시켰을 때 이송속도가 증가함에 따라 칩 두께의 증가와 함께 chip segment의 폭도 증가하여 chip segment 의 크기가 뚜렷이 증가함을 보였다. 또한 chip segment의 크기는 절삭속도 보다는 공구의 이송속도에 크게 영향을 받는 것을 알 수 있었고 분말의 입도 분포에도 크게 영향을 미치는 것으로 나타났다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 춘계학술발표회논문집(2)
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• pp.603-608
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• 1995

핵연료 성능과 uranium loading 향상을 위하여 제조한 $U_3$Si ribbon은 초정 $U_3$S $i_2$와 uranium solid solution으로 이루어져 있으며, 잘 발달된 dendrite 조직을 이루고 있다. 또한 grain size는 종전 ingot 제조방법에 비하여 약 1/20 정도로 미세하다. $700^{\circ}C$와 80$0^{\circ}C$에서 열처리한 $U_3$Si grain 내 twinning 현상은 이 온도구간에서 ordering 변태가 일어나는 것을 나타내며, TEM electron diffraction pattern 분석결과 twin은 {011}$_{fct}$ twin Plane을 따라 일어나는 것을 확인하였다.다.

• 한국결정성장학회지
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• 제25권1호
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• pp.13-19
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• 2015

Among the various possible factors affecting the Minority Carrier Life Time (MCLT) of the mc-Si crystal, dislocations formed during the cooling period after solidification were found to be a major element. It was confirmed that other defects such as grain boundary or twin boundary were not determinative defects affecting the MCLT because most of these defects seemed to be formed during the solidification period. With a measurement of total thickness variation (TTV) and bow of the silicon wafers, it was found that residual stress remaining in the mc-Si crystal might be another major factor affecting the MCLT. Thus, it is expected that better quality of mc-Si can be grown when the cooling process right after solidification is carried out as slow as possible.