• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.148-148
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• 2011

Recently, there have been many research activities to develop the large-area plasma source, which is able to generate the high-density plasma with relatively good uniformity, for the plasma processing in the thin-film solar cell and display panel industries. The large-area CCP sources have been applied to the PECVD process as well as the etching. Especially, the PECVD processes for the depositions of various films such as a-Si:H, ${\mu}c$-Si:H, Si3N4, and SiO2 take a significant portion of processes. In order to achieve higher deposition rate (DR), good uniformity in large-area reactor, and good film quality (low defect density, high film strength, etc.), the application of VHF (>40 MHz) CCP is indispensible. However, the electromagnetic wave effect in the VHF CCP becomes an issue to resolve for the achievement of good uniformity of plasma and film. Here, we propose a new electrode as part of a method to resolve the standing wave effect in the large-area VHF CCP. The electrode is split up a series of strip-type electrodes and the strip-type electrodes and the ground ones are arranged by turns. The standing wave effect in the longitudinal direction of the strip-type electrode is reduced by using the multi-feeding method of VHF power and the uniformity in the transverse direction of the electrodes is achieved by controlling the gas flow and the gap length between the powered electrodes and the substrate. Also, we provide the process results for the growths of the a-Si:H and the ${\mu}c$-Si:H films. The high DR (2.4 nm/s for a-Si:H film and 1.5 nm/s for the ${\mu}c$-Si:H film), the controllable crystallinity (~70%) for the ${\mu}c$-Si:H film, and the relatively good uniformity (1% for a-Si:H film and 7% for the ${\mu}c$-Si:H film) can be obtained at the high frequency of 40 MHz in the large-area discharge (280 mm${\times}$540 mm). Finally, we will discuss the issues in expanding the multi-electrode to the 8G class large-area plasma processing (2.2 m${\times}$2.4 m) and in improving the process efficiency.

• 대한기계학회논문집
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• 제19권1호
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• pp.122-131
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• 1995

The research trends for metal matrix composites have been on basic mechanical properties, fatigue behavior after aging and fractographic observations. In this study, the fatigue crack initiation as well as the fatigue crack growth behavior and the fracture mechanism were investigated through observations of the fracture surface on silicon carbide particles reinforced aluminum metal matrix composites(SiCp/Al). Based on the fractographic study done by scanning electron microscope and replica, crack growth path model and fracture mechanism are presented. The mechanical properties, such as the tensile strength, yield strength and elongation of SiCp/Al composites are improved in a longitudinal direction, however, the fatigue life is shorter than the basic Al6061 alloys. From fractographic observations, it is found that the failure mode is ductile in basic Ai6061 alloys. And because some SiC particles were pulled out from the matrix and a few SiC particles could be seen on the fracture surface of SiCp/Al, crack growth paths are believed to follow the interface of the matrix and its particles.

• 한국진공학회지
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• 제8권3B호
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• pp.322-326
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• 1999

We have investigated the growing process of a silicon film on the $CeO_2/Si$ surface. The silicon was deposited by using electron beam deposition method. The $CeO_2$(111) film was grown on a (111)-oriented silicon substrate at $700^{\circ}C$ at oxygen [partial pressure of $5\times10^{-5}$ Torr. To investigate the condition of epitaxial growth of si films on the $CeO_2/Si$ substrate, we deposited Si at various temperature니 The overlayer silicon was characterized by using x-ray diffraction(XRD). double crystal x-ray diffraction (DCXRD), and transmission electron microscopy (TEM). At temperature higher than $690^{\circ}C$, $CeO_2$ layer was observed at the $CeO_2/Si$ interface, which was formed by chemical reaction with silicon and oxygen dissociated from $CeO_2$. When silicon was deposited on the $CeO_2/Si$ at $620^{\circ}C$, silicon grew epitaxially along the (111)-direction.

• 한국세라믹학회지
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• 제50권6호
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• pp.378-383
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• 2013

Continuous fiber-reinforced ceramic matrix composites (CFCCs) have a complex distribution of porosity, consisting of interfiber micro pores and interbundle/interply macro pores. Owing to the complex geometry of the pores and fiber architecture, it is difficult to obtain representative microstructural features throughout the specimen volume with conventional, destructive ceramographic approaches. In this study, we introduce X-ray computed microtomography (X-ray ${\mu}CT$) to nondestructively analyze the microstructures of disk shaped and tubular $SiC_f$/SiC composites fabricated by the chemical vapor infiltration (CVI) method. The disk specimen made by stacking plain-woven SiC fabrics exhibited periodic, large fluctuation of porosity in the stacking direction but much less variation of porosity perpendicular to the fabric planes. The X-ray ${\mu}CT$ evaluation of the microstructure was also effectively utilized to improve the fabrication process of the triple-layered tubular SiC composite.

• 한국전기전자재료학회논문지
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• 제11권4호
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• pp.274-280
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• 1998

Polycrystalline $Sr_2Nb_2O_7$ ceramics with very high Curie temperature were sintered using the powder derived by the chemical coprecipitation method (CCP). The phase evolution and grain-orientation of sintered samples were examined by XRD, while sintering behavior, dielectric properties and polarization were studied by SEM and ferroelectric tester. Extremely high degree of grain-orientation was observed along the (0k0) direction, which resulted in anisotropic dielectric properties of the sintered samples, with the dielectric constant values approaching those for single crystal. Thin film fabrication of $Sr_2Nb_2O_7$ in the pyroniobate family was also attempted on $SiO_2$/Si(100), Pt/$SiO_2$/Si(100), Pt/Ti/$SiO_2$/Si(100) and Pt/$ZrO_2/SiO_2/Si_2(100)$ substrates, using metalorganic decomposition (MOD) process. Neodecanoate precursor solution was prepared by mixing strontium neodecanoate with niobium neodecanoate synthesized from niobium ethoxide. It was found that $Sr_2Nb_2O_7$ single phase appeared in XRD patterns the samples annealed above $950^{\circ}C$. The effect of substrate type on film microstructure and dielectric properties was observed.

• 한국재료학회지
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• 제13권10호
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• pp.677-682
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• 2003

SiC nanowires were synthesized by carbothermal reduction using metal catalysts. Synthesized nanowires had mean diameters of 30∼50 nm and several $\mu\textrm{m}$ length. The kind of catalysts affects form of SiC nanowire because of difference of growth mechanisms. These differences were made by catalyst's physical property and relative activities to the source gas. Ni acted a conventional catalyst of VLS growth mechanism. But, Case of Fe, SiC nanowire was grown by stable VLS growth mechanism without relation of growth conditions. SiC nanowire was grown by two step growth model using Cr catalyst. Conversion ratios to the SiC nanowire were increased with growth conditions. Case of Cr, conversion ratio was about 45% that was higher than other catalyst used. This high conversion ratio was obtained by the addition VS growth to radial direction on the as-grown nanowires.

• 한국결정성장학회지
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• 제12권6호
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• pp.283-287
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• 2002

초고집적 반도체 회로에서 Cu를 배선으로 쓰이기 위한 Cu 금속과 Si 기판사이의 확산방지막으로써 Zr(Si)N 박막을 연구하였다. Zr(Si)N 박막증착은 DC magnetron sputter으로 $Ar/N_2$의 혼합 gas를 사용한 reactive sputtering 방법을 이용하였다. 상온에서 ZrN 박막 증착시 Ar gas와 NE gas 비율이 48 : 2일 때 가장 낮은 비저항값을 가졌으며, 증착시 기판의 온도의 증가에 따라서 비저항값이 낮아졌다. 비저항값이 감소된 ZrN 박막일수록 (002)면의 방향성을 갖는 결정이 성장되었다. ZrN 박막의 Cu 확산방지 특성은 ZrN 박막에 Si을 첨가함으로써 개선될 수 있으며 지나치게 첨가될 경우에는 오히려 확산방지 특성이 감소되었다. 접착력 특성에서는 ZrN에 Si의 함유량이 증가함에 파라 개선되었다. 증착막의 특성은 XRD, 광학 현미경, scretch tester 그리고 $\alpha$-step 등을 사용하여 분석하였다.

• 한국결정성장학회지
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• 제10권1호
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• pp.5-12
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• 2000

Silicon carbide(SiC)는 뛰어난 전기적, 열적, 물리적 특성 때문에 내환경 전자소자용 반도체 재료로 널리 연구되고 있다. 본 연구에서는 화학기상증착법으로 단결정 6H-SiC 동종박막을 성장시키고 이의 성장 특성을 조사하였다. 특히, 몰리브덴 (Mo)-plate를 이용하여 SiC를 코팅하지 않은 graphite susceptor를 사용한 6H-SiC 동종박막 성장조건을 성공적으로 얻었다. 대기압 상태의 RF-유도가열식 챔버에서 CVD성장을 수행하였고, <1120> 방향으로 $3.5^{\circ}$off-axis된 기판을 사용하였다. 성장 박막의 결정성을 평가하기 위하여 Nomarski 관찰, 투과율 측정 , 라만 분광, XRD, 광발광(PL) 분광, 투과전자현미경(TEM) 측 정 등의 방법을 이용하였다. 이상과 같은 실험을 통하여, 본 연구에서는 성장온도 $1500^{\circ}C$, C/Si flow ratio ($C_3H_8$ 0.2 sccm, $SiH_4$ 0.3 sccm)인 성장조건에서 결정성이 가장 좋은 6H-SiC 동종박막을 얻을 수 있었다.

• 한국전기전자재료학회논문지
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• 제32권2호
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• pp.100-103
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• 2019

The change in vanadium amount according to the growth direction of vanadium-doped semi-insulated (SI) SiC single crystals using high-purity SiC powder was investigated. High-purity SiC powder and a porous graphite (PG) inner crucible were placed on opposite sides of SiC seed crystals. SI SiC crystals were grown on 2 inch 6H-SiC Si-face seeds at a temperature of $2,300^{\circ}C$ and growth pressure of 10~30 mbar of argon atmosphere, using the physical vapor transport (PVT) method. The sliced SiC single crystals were polished using diamond slurry. We analyzed the polytype and quality of the SiC crystals using high-resolution X-ray diffraction (XRD) and Raman spectroscopy. The resistivity of the SI SiC crystals was analyzed using contactless resistivity mapping (COREMA) measurements.

• 한국재료학회지
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• 제28권5호
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• pp.295-300
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• 2018

Effects of annealing temperature on the microstructure and mechanical properties through thickness of a Cu-3.0Ni-0.7Si alloy processed by differential speed rolling are investigated in detail. The copper alloy with a thickness of 3 mm is rolled to a 50 % reduction at ambient temperature without lubricant and subsequently annealed for 0.5 h at $200-900^{\circ}C$. The microstructure of the copper alloy after annealing is different in the thickness direction depending on the amount of the shear and compressive strain introduced by the rolling; the recrystallization occurs first in the upper roll side and center regions which are largely shear-deformed. The complete recrystallization occurs at an annealing temperature of $800^{\circ}C$. The grain size after the complete recrystallization is finer than that of the conventional rolling. The hardness distribution of the specimens annealed at $500-700^{\circ}C$ is not uniform in the thickness direction due to partial recrystallization. This ununiformity of hardness corresponds well to the amount of shear strain in the thickness direction. The average hardness and ultimate tensile strength has the maximum values of 250 Hv and 450 Mpa, respectively, in the specimen annealed at $400^{\circ}C$. It is considered that the complex mode of strain introduced by rolling directly affects the microstructure and the mechanical properties of the annealed specimens.