• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.307-312
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• 1996

In following addition of 0.3, -0.6, 0.8, 1.0 and 5 weight percent MgSiF66H2O studies have been made of the setting and hardening characteristics of ordinary portland cement. MgSiF66H2O retarded the setting time of ordinary portland cement and extended the induction pariod of the hydration. In ordinary portland cement the setting characteristics were drastically altered especially at high MgSiF66H2O contents. Evidence was also obtained by the formation of a KSiF6 which was very fine particle. The results wee as follows. 1. Slump was slightly decreased when MgSiF66H2O added. 2. Setting time was retarded depending on the amount of retarding agent 2 to 8 hours 3. Compressive strength was almost same or some increased in comparision with opc. 4. When MgSiF66H2O was added to cement paste K2SiF6 were formed It was fine-sized distributed uniformly in cement grain and caused retardation of cement setting.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.163-170
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• 1997

The retarding effects of MgSiF6.6H2O on the hydration of portland cement were studied. The setting time, flow value and compressive strength of mortar were measured and the mechanism of retardation was also studied by ion concentration in solution, SEM, BET, and X-ray diffraction. The results are as follows ; 1. Setting time was delayed by the addition of MgSiF6.6H2O. 2. The flow value of mortar decreases depending upon the amount of MgSiF6.6H2O. 3. The compressive strength was almost same or some increase on 28 days hydration. 4. The main retardation mechanism of MgSiF6 on the hydration of portland cement may be explained by the following hypothesis. MgSiF6 depressing the Ca++ and K+ ion concentration of cement paste solution be-cause of the recrystalization of K2SiF6 and CaF2 phase. The new products of K2SiF6 and CaF2 deposit on the surface of unhydrated cement powder and harzard the mass transfer through these layer. The low con-centration of Ca++, K+ ion in solution was decreasing the hydration rate of portland cement.

• Journal of the Korean Vacuum Society
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• v.4 no.S1
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• pp.1-6
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• 1995

Polycrystalline Si films have been used in many applications such as thin film transistors(TFT), image sensors and LSI applications. In this research deposition of Si films at low temperatures with remote plasma enhanced CVD from Si2H6-SiF4-H2 on SiO2 was studied and their crystallinity was investigated. It was condluded that growth of crystalline Si films was favorable with (1) low Si2H6 flow rates, (2) moderate plasma power, (3) moderate SiF4 flow rates, (4) moderate substrate temperature, and (5) suitable method of surface cleaning.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.05a
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• pp.279-280
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• 2003

실리콘웨이퍼 제조공정에서 폐기되는 HF에는 순수한 실라카만 함유되어 있지만 브라운관 업체에서 폐기되는 HF 폐액에는 유리의 조성에 따라서 다양한 성분들이 소량씩 함유되어 있다. 몰비로 Si:F=1:6이 되도록 조정한 후에 20% NaOH를 사용하여 pH를 6으로 조정하여 규불화소다를 얻고, 이어서 pH를 9로 조정하여 NaF를 었었다. 규불화소다에 NaCl, 칠레초석을 다양하게 첨가하여 금속 융제로 사용한 결과에 의하면 규불화소다의 양이 증가할수록 융제의 특성은 우수하였고, 가장 이상적인 첨가량은 50%~60%이었다. 따라서 각 공정에서 폐기되는 HF는 $Na_2SiF_{6}$와 NaF를 제조함으로서 재활용이 가능하였다.

• Journal of the Korean Vacuum Society
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• v.1 no.1
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• pp.145-152
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• 1992

Si surfaces exposed to CHF3/C2F6 gas plasmas ih reactive ion etching (RIE) have been characterized by X-ray photoelectron spectroscopy (XPS). CHF3/C2F6 gas plasma exposure of Si surface leads to the deposition of residual film containing carbon and fluorine. The narrow scan spectra of C 1s show various bonding states of carbon as C-Si, C-F/H, C-CFx(x $\leq$ 3), C-F, C-F2, and C-F3. The chemical bonding states of fluorine are described with F-Si, F-C and F-O. And the oxygen and silicon are also detected. The effects of parameters for reactive ion etching as CHF3/C2F6 gas ratio, RF power, and pressure are investigated.

• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1337-1340
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• 2001

The bulk photopolymerization of methyl methacrylate (MMA) with para-substituted phenylsilanes such as F-C6H4SiH3 (1), H3C-C6H4SiH3 (2), and H3CO-C6H4SiH3 (3) was performed to produce poly(MMA)s containing the respective silyl moiety as an end group. For all the hydrosilanes, the polymerization yields and the polymer molecular weights decreased, whereas the TGA residue yields and the relative intensities of Si-H IR stretching bands increased as the relative silane concentration over MMA increased. The polymerization yields and polymer molecular weights of MMA with 1-3 increased in the order of 3 < 1 < 2. These hydrosilanes influence significantly upon the photopolymerization of MMA as both chain-initiation and chain-transfer agents.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.66-69
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• 2002

This paper presents deposition and characterizations of microcrystalline silicon$({\mu}c-Si:H)$ films prepared by hot wire chemical vapor deposition at substrate temperature below $300^{\circ}C$. The $SiH_{4}$ concentration$[F(SiH_{4})/F(SiH_{4})+F(H_{2})]$ is critical parameter for the formation of Si films with microcrystalline phase. At 6% of silane concentration, deposited intrinsic ${\mu}c-Si:H$ films shows sufficiently low dark conductivity and high photo sensitivity for solar cell applications. P-type ${\mu}c-Si:H$ films deposited by Hot-Wire CVD also shows good electrical properties by varying the rate of $B_{2}H_{6}$ to $SiH_{4}$ gas. The solar cells with structure of Al/nip ${\mu}c-Si:H$/TCO/glass was fabricated with single chamber Hot-Wire CVD. About 3% solar efficiency was obtained and applicability of HWCVD for thin film solar cells was proven in this research.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.2
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• pp.107-116
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• 1993

Tungsten thin film was deposited on Si( 100) substrate by either Si substrate reduction of W$F_6$( case 1) or Si$H_4$ reduction of W$F_6$( case 2) in LPCVD system The morphology and properties of deposited films for both cases were examined. The crystal structure for both cases was determined to be bec (body centered cubic). The amount of tungsten and the grain size in thin films were increased as the film grows. From the experimental results and theoretical considerations, it can be understood that the tungsten thin film grows by the volmer-weber growth mode, that is, island growth. The detailed tungsten thin film growth mode is presented. It was also found that the initial polycrystal structure of tungsten thin film developed into single crystal structure as the film grew in thickness.

• 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-$NH_2$.

• Korean Journal of Materials Research
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• v.28 no.12
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• pp.709-713
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• 2018

To improve the etch rate of $Si_3N_4$ thin film, $H_2SiF_6$ is added to increase etching rate by more than two times. $SiO_3H_2$ is gradually added to obtain a selectivity of 170: 1 at 600 ppm. Moreover, when $SiO_3H_2$ is added, the etching rate of the $SiO_2$ thin film increases in proportion to the radius of the wafer. In $Si_3N_4$ thin film, there is no difference in the etching rate according to the position. However, in the $SiO_2$ thin film, the etching rate increases in proportion to the radius. At the center of the wafer, the re-growth phenomenon is confirmed at a specific concentration or above. The difference in etch rates of $SiO_2$ thin films and the reason for regrowth at these positions are interpreted as the result of the flow rate of the chemical solution replaced with fresh solution.