• Journal of Korea Water Resources Association
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• v.38 no.2
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• pp.133-142
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• 2005

The settling concentration of fine suspended solid particles(alumina(Al$_2$O$_3$) and quartz(SiO$_2$)) is investigated with the physico-chemical effects(initial concentration, pH and NaCl). Laboratory tests have confirmed the significant influence of increasing initial concentration and salinity which can lead to flocculation due to the intermolecular attraction. Furthermore, the influence of the pH value on the concentration-time corves of alumina has been on firmed. Besides a numerical model to predict the behaviour of cohesive deposit under still water is analyzed by solving the unsteady one-dimensional diffusion-advection equation with a explicit, implicit, Crank-Nicolson and finite difference scheme. The model predicts the existence of an equilibrium concentration. Application of the model with implicit centered difference to data from settling experiments shows a similar distribution.

• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.653-657
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• 2012

In this study, a molybdenum disilicide ($MoSi_2$) coating process was investigated by hydrogen reduction and Si-pack cementation. At first, the metallic Mo coating was carried out by hydrogen reduction of $MoO_3$ powder at $750^{\circ}C$ for various holding times (1, 2, 3 h) in hydrogen atmosphere. A $4.3{\mu}m$ thick metallic molybdenum thin film was formed at 3 h. $MoSi_2$ was obtained by Si-pack cementation on molybdenum thin film through hydrogen reduction processing. It was carried out using $Si:Al_2O_3:NH_4Cl=5:92:3$ (wt%) packs at $900^{\circ}C$ for various holding times (30, 60, 90 min) in Ar atmosphere. When the holding time was 90 min, a $MoSi_2$ layer was coated successfully and a $15.4{\mu}m$ thickness was observed.

• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05b
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• pp.26-27
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• 1992

The effect of activation and electroless nickel plating conditions on contact properties were investigated for selective electroless nickel plating of Si farers in order to obtain an optimum condition of contact hole filling. According to RCA prosess, p-type si 1 icon (100) surface was cleaned out and activated. The effects of temperture, DMAB concentration, time, and stirring iwere investigated for activation of p-type Si(100) surface. The optimal activation condition obtained was 0.5M HF, 1mM PdCl$_2$, 2mM EDTA, 7$0^{\circ}C$, 90sec under ultrasonic vibration. In electroless nickel plating, the effect of temperature, DMAB concentration, pH, and plating ti me were studied. The optimal plating condition found was 0. 10M NiS0$_4$.$H_2O$, 0.lIM Citrate, pH 6.8, 6$0^{\circ}C$, 30 minutes. The contact resistence of fi]ms wascomparatively low. It took 30 minutes to obtain 1$\mu$m thick film with 8$\mu$M DMAB concentration. The film surface roughness was improved with increasing temperature and decreasing pH of the plating solution. The best quality of the film was obtained with the condition of temperature 6$0^{\circ}C$ and pH 6.8. The micro-victors hardness of film was about 600Hv and was decreased wi th increasing particle size of plating layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.346-346
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• 2011

실리콘 나노와이어는 높은 표면적으로 인해 뛰어난 감지 능력을 가지는 재료 중 하나로 다양한 센서 응용 분야에 사용되고 있다. 이를 제작하는 방법에는 Micro Electro Mechanical Systems (MEMS) 공정을 이용한 Top-down 방식과 Vapor-Liquid-Solid (VLS) 공정을 이용한 Bottom-up 방식이 널리 사용되고 있다. 특히 Plasma-Enhanced Chemical Vapor Deposition(PECVD)와 Au 촉매를 이용한 Bottom-up 방식은 수십 나노미터 이하의 실리콘 나노와이어를 간단한 변수 조절을 통해 성장시킬 수 있다. 또한 Au/Si의 공융점인 363$^{\circ}C$보다 낮은 온도에서 $SiH_4$를 분해시킬 수 있어 열적 효과로 인한 손실을 줄일 수 있는 장점을 지니고 있다. 하지만 PECVD를 이용한 실리콘 나노와이어 성장은 VLS 공정을 통해 표면으로부터 수직으로 성장하게 되는데 이는 센서 응용을 위한 전극 사이의 수평 연결 어려움을 지니고 있다. 따라서 이를 피하기 위한 표면 성장된 실리콘 나노와이어가 요구된다. 본 연구에서는 PECVD VLS 공정을 이용하여 $HAuCl_4$를 촉매로 이용한 표면 성장된 Tree-like 실리콘 나노와이어를 성장시켰다. 공정가스로는 $SiH_4$와 이를 분해시키기 위해 Ar 플라즈마를 사용 하였고 웨이퍼 표면에 HAuCl4를 분사하고 고진공 상태에서 챔버 기판을 370$^{\circ}C$까지 가열한 후 플라즈마 파워(W) 및 공정 압력(mTorr)을 변수로 두어 실험을 진행하였다. 기존의 보고된 연구와 달리 환원된 금 입자 대신 $HAuCl_4$용액을 그대로 사용하였는데 이는 표면 조도(Surface roughness)를 가지는 Au 박막 상태로 존재하게 된다. 이 중 마루(Asperite) 부분에 PECVD로부터 발생된 실리콘 나노 입자가 상대적으로 높은 확률로 흡착하게 되어 실리콘 나노와이어의 표면성장을 유도하게 된다. 성장된 실리콘 나노와이어는 SEM과 EDS를 이용하여 직경, 길이 및 화학적 성분을 측정하였다. 직경은 약 100 nm, 길이는 약 10 ${\mu}m$ 정도로 나타났으며 Tree-like 실리콘 나노와이어가 성장되었다. 향후 전극이 형성된 기판위에 이를 직접 성장시킴으로써 이 물질의 I-V 특성을 파악 할 것이며 이는 센서 응용 분야에 도움이 될 것으로 기대된다.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1349-1354
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• 2010

The geometries and isomerization of the alkylidene silylenoid $H_2C$ = SiLiF as well as its insertion reactions with R-H (R = F, OH, $NH_2$) have been systematically investigated at the B3LYP/6-311+$G^*$ level of theory. The potential barriers of the three insertion reactions are 97.5, 103.3, and 126.1 kJ/mol, respectively. Here, all the mechanisms of the three reactions are identical to each other, i.e., an intermediate has been formed first during the insertion reaction. Then, the intermediate could dissociate into the substituted silylene ($H_2C$ = SiHR) and LiF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the three reactions are -36.4, -24.3, and 3.7 kJ/mol, respectively. Compared with the insertion reaction of $H_2C$ = Si: and R-H (R = F, OH and $NH_2$), the introduction of LiF makes the insertion reaction occur more easily. Furthermore, the effects of halogen (F, Cl, Br) substitution and inorganic salts employed on the reaction activity have also been discussed. As a result, the relative reactivity among the three insertion reactions should be as follows: H-F > H-OH > H-$NH_2$.

• Analytical Science and Technology
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• v.7 no.2
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• pp.187-191
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• 1994

A reactive intermediate 1,2-dihydropyridine derivative 2 has been prepared and isolated from the reaction of pyridine with $^tBuLi$ and trimethylchlorosilane in nonpolar condition at low temperature 2 has characterized by $^1H-NMR$ fine structure analysis with SPINX3. The mechanistic information of formation of 2 was obtained from synthesized 2,5-disubstituted pyridine derivatives 3 and 4.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.592-595
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• 1996

A silane dendrimer with 48 allylic end groups has been synthesized in excellent yield, via repetitive alkenylation-hydrosilation cycles. Starting with hexaallylethylenedisilane ((CH2=CHCH2)3SiCH2)2 as the core molecule (G0), a succession of alternate platinum catalyzed hydrosilation (Pt/C, 10% platinum content on active carbon) of all allyl groups with methyldichlorosilane and the allylation of all SiCl2 groups with allylmagnesium bromide in THF provided 3rd generation (G3) as carbosilane dendrimer. All the generations of dendrimer have been characterized by 1H and 13C NMR spectroscopy as well as elemental analysis.

• Bulletin of the Korean Chemical Society
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• v.17 no.11
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• pp.1040-1044
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• 1996

The catalytic dehydrocoupling of bis(1-sila-3-butyl)benzene, 1 by Cp2ZrCl2/Red-Al and Cp2ZrCl2/n-BuLi combination catalysts yielded a mixture of oily and solid polymers. While the catalytic dehydrocoupling of 2-phenyl-l,3-disilapropane, 2 by Cp2ZrCl2/n-BuLi combination catalyst produced a mixture of oily and solid polymers, the catalytic redistribution/dehydrocoupling of 2 by Cp2ZrCl2/Red-Al combination catalyst gave oily polymer. The dehydrocoupling of 1 and 2, unless the prior silane redistribution occurs, seems to initially produce a low-molecular-weight polymer, which then undergoes an extensive cross-linking reaction of backbone Si-H bonds, leading to an insoluble polymer.

• Journal of Industrial Technology
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• v.4
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• pp.37-41
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• 1984

Deposits of SiC has been formed by a chemical vapor deposition technique involving the application of gaseous mixture of $CH_3SiCl_3$ (MTS) and $H_2$ onto graphite substrate. These are non-fluid bed deposits prepared in an induction-heated reactor. From the experimental results, the deposition reaction of SiC is controlled by surface reaction mechanism at the temperature range between $1,100^{\circ}C$ and $1,400^{\circ}C$. The morphology of the SiC deposits changes from amorphous type to coarse, faceted structure as temperature increase.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.297-300
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• 2005

The characteristics of polycrystalline silicon thin-film transistors (poly-Si TFTs) fabricated using sputter deposited amorphous silicon (a-Si) precursor films are investigated. The a-Si films were deposited on flexible polymer substrates using argon-helium mixture gases to minimize the argon incorporation into the film. The precursor films were then laser annealed by using a XeCl excimer laser and a four-mask-processed poly-Si TFT was fabricated with fully self-aligned top gate structure. The fabricated pMOS TFT showed field-effect mobility of $32.4cm^2/V{\cdot}s$ and on/off ratio of $10^6$.