• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.230-235
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• 2010

In this paper, we controlled the deposition rate and reflective index with process conditions that are TCP power, gas flow ratio and bias for optical properties of $SiO_2$ thin film using TCP-CVD equipment. We obtained a excellent $SiO_2$ thin film which has a excellent uniformity (<1 [%]), deposition rate (0.28 [${\mu}m$/ min]) and reflective index (1.4610-1.4621) within 4" wafer with process conditions ($SiH_4:O_2$=50 : 100 [sccm], TCP power 1 [kW], bias 200 [W]) at [$300^{\circ}C$].

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.370-378
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• 2000

The composite restorative resins have their insufficient resistance to wear. The subsurface degradation within the restoration is considered to be associated with wear. The aim of this study was to evaluate the resistance to degradation of six commercial composite resins in an alkaline solution. The brands studied were Clearfil APX(Kuraray), Heliomolar(Vivadent), Surefil(Dentsply), TPH(Dentsply), Tetric Ceram(Vivadent), and Z100(3M). Preweighed discs of each brand were exposed 0.1N NaOH solution at $60^{\circ}C$. After 14 days they were removed, neutralized with HCL, washed with water and dried to constant mass at $60^{\circ}C$. Resistance to degradation was evaluated on the basis of the following parameters: (a) mass loss(%) - determined from pre-and post-exposure specimen weights; (b) Si loss (ppm)-obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth$({\mu}m)$ - measured microscopically (SEM) from polished circular sections of exposed specimens. The results were as follows: 1. The mass loss was in descending order by Z100, TC H, S, CL, TPH and in the range of $0.45\sim3.64%$ 2. The degradation layer depth was in descending order by H, Z100, S, TC, TPH, CL and in the range of $10.85\sim73.38{\mu}m$ 3. For the Si concentration, Z100 was the highest of all 4. The highly significant correlation(r=0.81, p<0.05) was observed between mass loss and degradation depth. 5. Under scanning electronmicroscopy, the degradation of connection between resin matrix and fillers was observed 2 weeks after soaking in NaOH solution.

• Journal of the Korean Chemical Society
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• v.38 no.7
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• pp.473-479
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• 1994

Tungsten thin film was deposited on p-(100) silicon substrate by using the LPCVD(low pressure chemical vapor deposition) technique. $WF_6$ was used as a source gas for tungsten and $SiH_4$ was used as a reducing gas for $WF_6$. Tungsten thin film was deposited by either SiH4 or Si substrate reduction of $WF_6$ under cold-wall condition and it was deposited by $SiH_4$ reduction of $WF_6$ under hot-wall condition. The crystal structure of deposited thin film under both conditions were identified to be bcc (body centered cubic). The physical and electrical properties of deposited thin films were investigated. The deposited film under hot-wall condition changed to $WSi_2$ film by the annealing under $800^{\circ}C.$ From the experimental results and theoretical considerations, the change of the crystal structure of the thin film by annealing was discussed. $WSi_2$ thin film, which was known to have good compatibility with Si substrate, could be produced under hot-wall condition although the film properties were superior under cold-wall condition.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.2
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• pp.56-59
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• 2001

Thin films of hydrogenated amorphous silicon (a-Si : H) of different compositions were deposited on Si(100) wafer and glass by RF plasma-enhanced chemical vapor deposition (PECVD). In the present work, we have investigated the effect of the If. power on the properties, such as optical band gap, transmittance and crystallinity, of crystalline silicon thin films. Raman data show that the material consists of an amorphous and crystalline phase for the co-presence of two peaks centered at 480 and 520cm$^{-1}$. X-ray spectra confirmed of crystallites with (111) orientation at 300w The transmittance of thin films was measured by UV-VIS spectrophotometer. In addition, Si-H chemical bondings were studied by Fourier Transform Infrared (FT-IR) spectroscopy.

• Journal of Surface Science and Engineering
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• v.34 no.5
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• pp.503-509
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• 2001

Thin films of hydrogenated amorphous silicon (a-Si : H) and hydrogenated amorphous silicon carbide (a-SiC:H) of different compositions were deposited on Si(100) wafer and glass by RF plasma-enhanced chemical vapor deposition (RF-PECVD). In the present work, we have investigated the effects of the RF power on the properties, such as optical band gap, transmittance and crystallinity. The Raman data show that the a-Si:H material consists of an amorphous and crystalline phase for the co-presence of two peaks centered at 480 and $520 cm^{-1}$ . The UV-VIS data suggested that the optical energy band gap ($E_{g}$ ) is not changed effectively with RF power and the obtained $E_{g}$(1.80eV) of the $\mu$c-Si:H thin film has almost the same value of a-Si:H thin film (1.75eV), indicating that the crystallity of hydrogenated amorphous silicon thin film can mainly not affected to their optical properties. However, the experimental results have shown that$ E_{g}$ of the a-SiC:H thin films changed little on the annealing temperature while $E_{g}$ increased with the RF power. The Raman spectrum of the a-SiC:H thin films annealed at high temperatures showed that graphitization of carbon clusters and microcrystalline silicon occurs.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1095-1100
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• 2000

we have proposed a three-dimensional GLE approach to gas-surface reactive scattering, model H + H $${\rightarrow}$H_2/Si(100)-(2$ ${\times}$1) system, and the implementation of 3D GLE method on the hydrogen on silicon surface has been presented. The formalism and algori thm of the 3D GLE are worked properly in the reactive scattering system. The calculated normal mode frequencies of surface vibrations were almost identical to previous harmonic slab calculations. The reaction probabilities were calculated for two energies. The calculations show that a very large amount of energy is transferred in surface in low energy scattering. Three different types of reaction mechanisms has been observed, which can not be shown in flat and rigid surface models. Further work on the reaction mechanisms and calculations of the vibrational and rotation distributions of products is in progress. The results will be reported elsewhere soon.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.162-163
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• 2007

The dry etching of Si was investigated using direct dc biasing to the Si substrate. The TCP type etching system with a feed-through for applying a dc bias was used in the etching. The applied dc bias and ICP power was varied to examine the effect on the etching at the fixed chamber pressure and $SF_6$ flow rate of 10 mTorr and 10 sccm during. When the plasma was generated at ICP power of 100 W, the etch rate of Si was increased with the bias for the biased samples. However, the etching of Si for the non-biased sample was enhanced for the increased ICP power.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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• pp.128-131
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• 2009

Silicon carbide (SiC) has attracted significant attention for high frequency, high temperature and high power devices due to its superior properties such as the large band gap, high breakdown electric field, high saturation velocity and high thermal conductivity. We performed Al ion implantation processes on n-type 4H-SiC substrate using a SILVACO ATHENA numerical simulator. The ion implantation model used Monte-Carlo method. We simulated the effect of channeling by Al implantation in both 0 off-axis and 8 off-axis n-type 4H-SiC substrate. We have investigated the effect of varying the implantation energies and the corresponding doses on the distribution of Al in 4H-SiC. The controlled implantation energies were 40, 60, 80, 100 and 120 keV and the implantation doses varied from $2{\times}10^{14}$ to $1{\times}10^{15}\;cm^{-2}$. The Al ion distribution was deeper with increasing implantation energy, whereas the doping level increased with increasing dose. The effect of post-implantation annealing on the electrical properties of Al-implanted p-n junction diode were also investigated.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.7
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• pp.293-297
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• 2003

Silicon dioxide (SiO$_2$) layers were fabricated on Si$_3$N$_4$/SiO$_2$/Si layer structures by low pressure chemical vapor deposition (LPCVD). Potassium and aluminum were then coimplanted by implanting potassium ions with the energy of 100 ［keY］ and dose of 5x10$^{16}$ [cm￣$^2$］ and 1x10$^{17}$ [cm￣$^2$］ into an aluminum buffer layer on the SiO$_2$Si$_3$N4/SiO$_2$/Si structure. The pH, pNa, and pK ion sensitivities of the resulting layers were investigated and compared to those of as-deposited silicon dioxide layer. The pK-sensitivity of the silicon dioxide was enhanced by the K and Al coimplantation. On the contrary, the pH and pNa-sensitivities of the coimplanted silicon dioxides were quite lower than that of the as-deposited silicon dioxide.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.65-71
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• 1996

Decomposition reaction of methanol was conducted on Ni-Cu/SiO$_2$catalysts with several variables. Variables used in this study are S.V(Space Velocity), partial pressure of methanol, reaction temperature, and composition rate of Ni-Cu. The range of S.V is 10,000-30,000h$\^$-1/, the temperature range is 150-400$^{\circ}C$ and values of Cu/(Ni＋Cu) are 0, 0.25, 0.5, 0.75, and 1. Over Ni/SiO$_2$, and Ni-Cu/SiO$_2$, the conversion rate of decomposition reaction of methanol arrived at 100% with increasing of temperature. At this time the selectivity of CO on Ni/SiO$_2$, was suddenly decreased, but on Ni-Cu/SiO$_2$, it was still sustained highly. The main products of reaction were CO and H$_2$, and by-products were CO$_2$ and CH$_4$mainly.