• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.153-159
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• 1997

A thermally-driven polysilicon microactuator has been fabricated using surface micromachining techniques. It consists of P-doped polysilicon as a structural layer and TEOS(tetraethylorthosilicate) oxide as a sacrificial layer. The polysilicon was annealed for the relaxation of residual stress which is the main cause to its deformation such as bending and buckling. And newly developed HF GPE(gas-phase etching) process was also employed to eliminate the troublesome stiction problem using anhydrous HF gas and CH$_{3}$OH vapor, and successfully fabricated the microactuators. The actuation is incurred by the thermal expansion due to the current flow in the active polysilicon cantilever, which motion is amplified by lever mechanism. The moving distance of polysilicon microactuator was experimentally conformed as large as 21 .mu. m at the input voltage level of 10V and 50Hz square wave. The actuating characteris- tics are also compared with the simulalted results considering heat transfer and thermal expansion in the polysilicon layer. This microactuator technology can be utilized for the fabrication of MEMS (microelectromechanical system) such as microrelay, which requires large displacement or contact force but relatively slow response.

• Journal of the Korean Ceramic Society
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• v.31 no.2
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• pp.206-212
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• 1994

Effects of the film deposition process parameters on the properties such as deposition rate, etch rate, refractive index, stress and step coverage of plasma enhanced chemical vapor deposited (PECVD) tetraethylorthosilicate glass (TEOS) SiO2 film were investigated and analysed using SEM, FTIR and SIMS techniques. Increasing TEOS flow or decreasing O2 flow increased the deposition rate and the compressive stress of the oxide film but produced a less denser film. The deposition rate decreased owing to the decrease in the sticking coefficient of the TEOS and the O2 molecules onto the substrate Si with increasing the substrate temperature. Increasing the substrate temperature produced a denser film with a lower etch rate and the higher refractive index by lowering SiOH and moisture contents. Increasing the rf power increases the ion bombardment energy. This increase in energy, in turn, increases the deposition rate and tends to make the film denser. No appreciable changes were found in the deposition rate but the refractive index and the stress of the film decreased with increasing the deposition pressure. The carbon content in the plasma TEOS CVD oxide film prepared under our standard deposition conditions were very low according to the SIMS analysis results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.181-181
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• 2010

Few-walled carbon nanotubes (FWNTs)-based field emitters with long term stability are fabricated by using a spray method. Tetraethylorthosilicate (TEOS) sol as a binder was mixed with dispersed solution of FWNTs to enhance the adhesion of FWNTs on the cathode substrate. Due to the strong intermolecular interaction of TEOS to the functional groups attached on CNTs and substrate, CNTs are tightly adhered to the cathode electrode when heat treatment is performed at $150^{\circ}C$ for 1 hour, resulting in a stable electron emission of CNT emitters for long time. Excellent field emission characteristics were exhibited, with a large field enhancement factor and low turn-on voltage, comparable to those of CNT emitters fabricated by a screen printing of CNT paste. Therefore, FWNTs / TEOS hybrid films could be utilized as an alternative for the efficient and reliable field emitters.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2367-2370
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• 2014

"Cat's eye"-shaped $[^{57}Co]CoO@SiO_2$ core-shell nanostructure was prepared by the reverse microemulsion method combined with radioisotope technique to investigate a potential imaging agent for a single photon emission computed tomography (SPECT) in nuclear medicine. The core cobalt oxide nanorods were obtained by thermal decomposition of $Co-(oleate)_2$ precursor from radio isotope Co-57 containing cobalt chloride and sodium oleate. The $SiO_2$ coating on the surface of the core cobalt oxide nanorods was produced by hydrolysis and a condensation reaction of tetraethylorthosilicate (TEOS) in the water phase of the reverse microemulsion system. In vivo test, micro SPECT image was acquired with nude mice after 30 min of intravenous injection of $[^{57}Co]CoO@SiO_2$ core-shell nanostructure.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.4 s.37
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• pp.345-349
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• 2005

Low resistive ($300{\mu}{\Omega}$-cm) W-C-N films have been deposited on tetraethylorthosilicate (TEOS) interlayer dielectric by atomic layer deposition (ALD) with $WF_6-N_2-CH_4$ gas. The exposure cycles of $N_2$ and $CH_4$ are synchronized with pulse plasma. The W-C-N films on TEOS layer follow the ALD mechanism and keep constant deposition rate of 0.2 nm/cycle from 10 to 100 cycles. As a diffusion barrier for Cu interconnection the W-C-N films maintain amorphous phase and Cu inter-diffusion is not occurred even at $800^{\circ}C$ for 30 min.

• Transactions on Electrical and Electronic Materials
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• v.12 no.3
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• pp.119-122
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• 2011

A series of mesoporous silicalites was synthesized using different compositions of tetraethylorthosilicate and methyltriethoxysilane (MTES) as the silica source. Cetyltrimethylammonium bromide was used as the organic template. Their detailed pore structures were investigated by transmission electron microscopy, X-ray diffraction, and N2 adsorption method. The thermal properties of these silicalites were studied by thermogravimetric analysis. The increased amount of MTES destroyed mesoporous channels and reduced pore sizes from 3.4 nm to 2.8 nm in calcined silicalites. The calcined silicalite transformed completely into an amorphous state at 30% MTES loading. Methyl pending groups of MTES hindered the structural ordering of ≡Si-O- frameworks, resulting in an amorphous structure. This was caused by the insufficient formation of supramolecular assembly with the organic template. No capillary condensation step was found in MS 7/3 silicalite. The other capillary condensation steps shifted toward the lower relative pressure with increasing MTES content, indicating the reduction of pore sizes.

• Journal of environmental and Sanitary engineering
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• v.13 no.3
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• pp.58-65
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• 1998

Monodispersed $SiO_2/ZnO$ composite fine powders were prepared by Sol-Gel processing and their surface electrical and UV absorbance properties were investigated. Pseudomorph ZnO fine powders were microcapsuled by $SiO_2/ZnO$ sol fabricated using TEOS[tetraethylorthosilicate, purity 98% and ethanol as a solvent with $NH_3$ catalyst. The effects of experimental parameters such as molar ratio of starting materials on the final particle size and shape of $SiO_2/ZnO$ composite fine powder were discussed. As a result, we could controlled the size of monodispersed $SiO_2/ZnO$ composite fine powders without agglomeration, as well as the good dispersibility in aquous solution. The prepared powders were observed to have the mean particle sizes of $0.26-0.78{\mu}m$ with standard deviations of $0.020-0.063{\mu}m$.

• Journal of Powder Materials
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• v.24 no.2
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• pp.87-95
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• 2017

Lithium silicate, a lithium-ion conducting ceramic, is coated on a layer-structured lithium nickel manganese oxide ($LiNi_{0.7}Mn_{0.3}O_2$). Residual lithium compounds ($Li_2CO_3$ and LiOH) on the surface of the cathode material and $SiO_2$ derived from tetraethylorthosilicate are used as lithium and silicon sources, respectively. Powder X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy analyses show that lithium silicate is coated uniformly on the cathode particles. Charge and discharge tests of the samples show that the coating can enhance the rate capability and cycle life performance. The improvements are attributed to the reduced interfacial resistance originating from suppression of solid-electrolyte interface (SEI) formation and dissolution of Ni and Mn due to the coating. An X-ray photoelectron spectroscopy study of the cycled electrodes shows that nickel oxide and manganese oxide particles are formed on the surface of the electrode and that greater decomposition of the electrolyte occurs for the bare sample, which confirms the assumption that SEI formation and Ni and Mn dissolution can be reduced using the coating process.

• Journal of Powder Materials
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• v.23 no.6
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• pp.442-446
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• 2016

The sol-gel method is the simplest method for synthesizing monodispersed silica particles. The purpose of this study is to synthesize uniform, monodisperse spherical silica nanoparticles using tetraethylorthosilicate (TEOS) as the silica precursor, ethanol, and deionized water in the presence of ammonia as a catalyst. The reaction time and temperature and the concentration of the reactants are controlled to investigate the effect of the reaction parameters on the size of the synthesized particles. The size and morphology of the obtained silica particles are investigated using transmission electron microscopy and particle size analysis. The results show that monodispersed silica particles over a size range of 54-504 nm are successfully synthesized by the sol-gel method without using any additional process. The nanosized silica particles can be synthesized at higher TEOS/$H_2O$ ratios, lower ammonia concentrations, and especially, higher reaction temperatures.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.141-147
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• 2005

Nanomaterial $TiO_2-SiO_2$ was synthesized by hydrolysis and condensation process using 2-propanol(2-PrOH) and was characterized by FT-IR, DSC, XRD and FE-SEM. FT-IR spectra were measured to investigate Ti-0-Si absorption peak. DSC thermal analysis results appllied to Ozawa equation were used to calculate to activation energy of crystallization. It was found that the changes of X-ray diffraction patterns and FWHM obtained XRD measurement depended on calcination temperature. In FE-SEM analysis, particle size changed by quantity changes of Ti-alkokide.