• Korean Journal of Materials Research
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• v.21 no.2
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• pp.100-105
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• 2011

The relative viscosity was measured at different filler loadings for a cycloaliphatic epoxy resin and hexahydro-4-methylphthalic anhydride hardener system filled with micro/nano hybrid silica. Various empirical models were fitted to the experimental data and a fitting parameter such as critical filler fractions (${\phi}_{max}$) was estimated. Among the models, the Zhang-Evans model gave the best fit to the viscosity data. For all the silica loadings used, ln (relative viscosity) varied linearly with filler loadings. Using the Zhang-Evans model and the linearity characteristics of the viscosity change, simple methods to predict the relative viscosity below ${\phi}_{max}$ are presented in this work. The predicted viscosity values from the two methods at hybrid silica fractions of $\phi$ = 0.086 and 0.1506 were confirmed for a micro:nano = 1:1 hybrid filler. As a result, the difference between measured and predicted values was less than 11%, indicating that the proposed predicting methods are in good agreement with the experiment.

• Korean Journal of Materials Research
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• v.21 no.2
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• pp.83-88
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• 2011

Nano-technology is a super microscopic technology to deal with structures of 100 nm or smaller. This technology also involves the developing of $TiO_2$ materials or $TiO_2$ devices within that size. The aim of the present paper is to synthesize $WO_x$ doped nano-$TiO_2$ by the Sonochemistry method and to evaluate the effect of different percentages (0.5-5 wt%) of tungsten oxide load on $TiO_2$ in methylene blue (MB) elimination. The samples were characterized using such different techniques as X-ray diffraction (XRD), TEM, SEM, and UV-VIS absorption spectra. The photo-catalytic activity of tungsten oxide doped $TiO_2$ was evaluated through the elimination of methylene blue using UV-irradiation (315-400nm). The best result was found with 5 wt% $WO_x$ doped $TiO_2$. It has been confirmed that $WO_x-TiO_2$ could be excited by visible light (E<3.2 eV) and that the recombination rate of electrons/holes in $WO_x-TiO_2$ declined due to the existence of $WO_x$ doped in $TiO_2$.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.198-202
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• 2006

Cadmium selenide (CdSe) nanoparticles with the diameter of about 3.4nm have been synthesized from the mixed aqueous solution of distilled water and diethanolamine at room temperature. The cadmium chloride ($CdCl_2$), sodium selenosulfate ($Na_2SeSO_3$) were used as the cadmium and selenium source, respectively. The properties of CdSe nanoparticles were characterized by using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV-Vis measurements. CdSe nanoparticles were analyzed to be cubic phase with the absorption excition peaks between 540 and 600 nm. CdSe nanoparticles also showed red-shifted excition peaks with increasing the sonication time. This paper mainly presents the sonication effects on the formation of CdSe nanoparticles prepared from the mixed aqueous solution of distilled water and diethanolamine.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.151-156
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• 2006

A method for fabrication of nano-scale GaN structure by inductively coupled plasma etching is proposed, exploiting a thermal dewetting of Pt thin film as an etch mask. The nano-scale Pt metal islands were formed by the dewetting of 2-dimensional film on $SiO_2$ dielectric materials during rapid thermal annealing process. For the case of 30 nm thick Pt films, pattern formation and dewetting was initiated at temperatures greater $600^{\circ}C$. Controlling the annealing temperature and time as well as the thickness of the Pt metal film affected the size and density of Pt islands. The activation energy for the formation of Pt metal island was calculated to be 23.2 KJ/mole. The islands show good resistance to dry etching by a $CF_4$ based plasma for dielectric etching indicating that the metal islands produced by dewetting are suitable for use as an etch mask in the fabrication of nano-scale structures.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.208-208
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• 2003

저온균일침전법(HPPLT)으로 제조된 TiO$_2$나노분말은 10$0^{\circ}C$이하의 온도에서 rutile상을 얻을 수 있다. 또한, rutile에서 anatase로의 상변화는 합성시간, 가열속도, 반응온도 그리고 음이온 첨가에 의해 일어난다고 보고되어졌지만, 금속양이온들에 의한 상변화는 알려진 바가 없다. 따라서, 다양한 양이온을 첨가하여 저온균일침전법에서 TiO$_2$의 상변화가 어떻게 일어나는지를 조사하였다. 출발원료인 TIC1$_4$를 사용하여 가수분해하여 0.67M의 TiOCl$_2$을 얻었다. 얻어진 TiOCl$_2$ 수용액에 각각 0.01M의 금속염화물(ZrOCl$_2$, NiCl$_2$, CuCl$_2$, FeCl$_3$, AlCl$_3$ 그리고 NbCl$_{5}$)을 첨가한 후 반응기에 넣고 10$0^{\circ}C$에서 4시간동안 가열하였다 가열한 후 얻어진 침전물에 NaOH 수용액을 이용하여 PH 7-8로 중화한 후 증류수로 Cl$^{-}$이온이 제거될 때까지 충분히 세척하였다. 세척된 침전물을 105$^{\circ}C$에서 24h동안 건조하여 분말을 얻었고, rutile에서 anatase로의 상변화특성을 관찰하기 위하여 XRD, SEM, TEM, ICP 분석을 실시하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.120-120
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• 2003

The metallic oxide nanomaterials including ZnO, Ga$_2$O$_3$, TiO$_2$, and SnO$_2$ have been synthesized by a number of methods including laser ablation, arc discharge, thermal annealing procedure, catalytic growth processes, and vapor transport. We have been interested in preparing the nanomaterials of Ga$_2$O$_3$, which is a wide band gap semiconductor (E$_{g}$ =4.9 eV) and used as insulating oxide layer for all gallium-based semiconductor. Ga$_2$O$_3$ is stable at high temperature and a transparent oxide, which has potential application in optoelectronic devices. The Ga$_2$O$_3$ nanoparticles and nanobelts were produced using GaN single crystals, which were grown by flux method inside SUS$^{TM}$ cell using a Na flux and exhibit plate-like morphologies with 4 ~ 5 mm in size. In these experiments, the conventional electric furnace was used. GaN single crystals were pulverized in form of powder for the growth of Ga$_2$O$_3$ nanomaterials. The structure, morphology and composition of the products were studied mainly by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM).).

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.71-71
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• 2003

Hot embossing has been widely accepted as an alternative to photolithography in generating patterns on polymeric substrates. The optimization of embossing process should be accomplished based on polymer substrate materials. In this paper, the effect of polymer substrates on nano scale hot embossing process was studied. Silicon molds with nano size patterns were fabricated by e-beam direct writing. Molds were coated with self-assembled monolayer (SAM) of (1, 1, 2.2H -perfluorooctyl)-trichlorosilane to reduce the stiction between mold and substrates. For an embossing, pressure of 55, 75 bur, embossing time of 5 min and temperature of above transition temperature were peformed. Polymethylmethacrylates (PMMA) with different molecular weights of 450,000 and 950,000, MR-I 8010 polymer (Micro Resist Technology) and polyaliphatic imide copolymer were applied for hot embossing process development in nano size. These polymers were spun coated on the Si wafer with the thickness between 150 and 200 nm. The nano size patterns obtained after hot embossing were observed and compared based on the polymer properties by scanning electron microscopy (SEM). The imprinting uniformity dependent on the Pattern density and size was investigated. Four polymers have been evaluated for the nanoimprint By optimizing the process parameters, the four polymers lead to uniform imprint and good pattern profiles. A reduction in the friction for smooth surfaces during demoulding is possible by polymer selection.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.63-63
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• 2003

The nanotopography of silicon wafers has emerged as an important factor in the STI process since it affects the post-CMP thickness deviation (OTD) of dielectric films. Ceria slurry with surfactant is widely applied to STI-CMP as it offers high oxide-to-nitride removal selectivity. Aiming to control the nanotopography impact through ceria slurry characteristics, we examhed the effect of surfactant concentration and abrasive size on the nanotopography impact. The ceria slurries for this study were produced with cerium carbonate as the starting material. Four kinds of slurry with different size of abrasives were prepared through a mechanical treatment The averaged abrasive size for each slurry varied from 70 nm to 290 nm. An anionic organic surfactant was added with the concentration from 0 to 0.8 wt %. We prepared commercial 8 inch silicon wafers. Oxide Shu were deposited using the plasma-enhanced tetra-ethyl-ortho-silicate (PETEOS) method, The films on wafers were polished on a Strasbaugh 6EC. Film thickness before and after CMP was measured with a spectroscopic ellipsometer, ES4G (SOPRA). The nanotopogrphy height of the wafer was measured with an optical interferometer, NanoMapper (ADE Phase Shift)

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.39-39
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• 2003

Molecular dynamics (MD) simulation was performed to study the stress induced grain boundary migration caused by the interaction of dislocations with a gain boundary. The simulation was carried out in a Ni block (295020 atoms) with a ∑ = 5 (210) grain boundary and an embedded atom potential for Ni was used for the MD calculation. Stress was provided by indenting a diamond indenter and the interaction between Ni surface and diamond indenter was assumed to have a fully repulsive force to emulate a faction free surface. Results showed that the indentation nucleated perfect dislocations and the dislocations produced stacking faults in the form of a parallelepiped tube. The parallelepiped tube consisted of two pairs of parallel dislocations with Shockley partials and was produced successively during the penetration of the indenter. The dislocations propagated along the parallelepiped slip planes and fully merged onto the ∑ = 5 (210) grain boundary without emitting a dislocation on the other grain. The interaction of the dislocations with the grain boundary induced the migration of the grain boundary plane in the direction normal to the boundary plane and the migration continued as long as the dislocations merged onto the grain boundary plane. The detailed mechanism of the conservative motion of atoms at the gram boundary was associated with the geometric feature of the ∑ = 5 (210) grain boundary.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.987-991
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• 2009

We report growth of vertically well-aligned zinc oxide (ZnO) nanorods on indium-tin oxide (ITO)/glass substrates using a simple aqueous solution method at low temperature via control of the ZnO seed layer morphology. ZnO nanoparticles acting as seeds are pre-coated on ITO-coated glass substrates. by spin coating to control distribution and density of the ZnO seed nanoparticles. ZnO nanorods were synthesized on the seed-coated substrates in a dipping process into a main growth solution. It was found that the alignment of ZnO nanorods can be effectively manipulated by the spin-coating speed of the seed layer. A grazing incidence X-ray diffraction pattern shows that the ZnO seed layer prepared using the higher spin-coating speed is of uniform seed distribution and a flat surface, resulting in the vertical growth of ZnO nanorods aligned toward the [0001] direction in the main growth process.