• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.7
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• pp.352-357
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• 2004

The composites were fabricated, respectively, using 61vol.% SiC - 39vol.% TiB$_2$ and using 61vo1.% SiC - 39vo1.% WC powders with the liquid forming additives of 12wt% $Al_2$O$_3$＋Y$_2$O$_3$ by pressureless annealing at 180$0^{\circ}C$ for 4 hours. Reactions between SiC and transition metal TiB$_2$, WC were not observed in this microstructure. The result of phase analysis of composites by XRD revealed SiC(6H), TiB$_2$ and YAG(Al$_{5}$Y$_3$O$_{12}$) crystal phase on the SiC-TiB$_2$, and SiC(2H), WC and YAG(Al$_{5}$Y$_3$O$_{12}$) crystal phase on the SiC-WC composites. $\beta$\$\longrightarrow$$\alpha$-SiC phase transformation was ocurred on the SiC-TiB$_2$, but $\alpha$\$\longrightarrow$$\beta$-SiC reverse transformation was not occurred on the SiC-WC composites. The relative density, the vicker's hardness, the flexural strength and the fracture toughness showed respectively value of 96.2%, 13.34GPa, 310.19Mpa and 5.53Mpaㆍml/2 in SiC-WC composites. The electrical resistivity of the SiC-TiB$_2$ and the SiC-WC composites is all positive temperature coefficient resistance(PTCR) in the temperature ranges from $25^{\circ}C$ to 50$0^{\circ}C$. 2.64${\times}$10-2/$^{\circ}C$ of PTCR of SiC-WC was higher than 1.645${\times}$10-3/$^{\circ}C$ of SiC-TiB$_2$ composites.posites.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.634-638
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• 2004

Titanium silicalite-1 (TS-1) molecular sieve was produced by microwave heating of amorphous titanium-containing solid precursors after impregnation with aqueous TPAOH solution. $SiO_2-TiO_2$ xerogel, sub-micron sized $SiO_2-TiO_2$ prepared by thermal plasma process, and Ti-containing mesoporous silica, Ti-HMS, were tested as the solid phase substrates. Highly crystalline product was obtained within 30 min. after microwave irradiation with yields over 90% using $SiO_2-TiO_2$ xerogel, which showed essentially identical physicochemical properties to TS-1 prepared by conventional hydrothermal method. Excellent catalytic activity was also obtained for 1-hexene epoxidation using $H_2O_2.\;SiO_2-TiO_2$ particles prepared by thermal plasma and Ti-HMS were found inferior as a substrate for TS-1, probably due to difficulties in wetting the surface uniformly with TPAOH.

• Proceedings of the Materials Research Society of Korea Conference
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• 1997.05a
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• pp.102-102
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• 1997

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.283.2-283.2
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• 2013

The variation of chemical and interfacial state during the growth of Ta2O5 films on the Si substrate by atomic layer deposition (ALD) was investigated using in-situ synchrotron radiation photoemission spectroscopy. A newly synthesized liquid precursor Ta(NtBu)(dmamp)2Me was used as the metal precursor, with Ar as a purging gas and H2O as the oxidant source. The core-level spectra of Si 2p, Ta 4f, and O 1s revealed that Ta suboxide and Si dioxide were formed at the initial stages of Ta2O5 growth. However, the Ta suboxide states almost disappeared as the ALD cycles progressed. Consequently, the Ta5+ state, which corresponds with the stoichiometric Ta2O5, only appeared after 4.0 cycles. Additionally, tantalum silicate was not detected at the interfacial states between Ta2O5 and Si. The measured valence band offset value between Ta2O5 and the Si substrate was 3.08 eV after 2.5 cycles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.934-940
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• 2001

Magnetic properties were investigated for Si/SiO$_2$/NiFe(300 )/A1$_2$O$_3$(t)/Co(200 ) junction related with the parameters of $Al_2$O$_3$. Insulating $Al_2$O$_3$ layer was formed by depositing a 5~40 thick Al layer, followed by a 90~120s RF plasma oxidation in an $O_2$ atmosphere. Magnetoresistance was not observed for tunnel junction with 5~10 thick Al layer, but magnetoresistance was observed large for tunnel junction with 15~40 thick Al layer. Oxidation time did not largely influence magnetoresistance. Tunnel magnetoresistance effect depended on magnetization behavior of two ferromagnetic layers. Tunneling junction was confirmed through nonlinear I-V curve. In this work, tunneling magnetoresistance(TMR) up to 30 % was observed. This apparent TMR is an artifact of the nonuniform current flow over the junction in the cross geometry of the electrodes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.386-389
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• 2009

The electrical characteristics and annealing effects of tunneling dielectrics stacked with $SiO_2$ and $Si_{3}N_{4}$ were investigated. I-V characteristics of band gap engineered tunneling gate stacks consisted of $Si_{3}N_{4}/SiO_2/Si_{3}N_{4}$ (NON), $SiO_2/Si_{3}N_{4}/SiO_2$ (ONO) dielectrics were evaluated and compared with $SiO_2$ single layer using the MOS (metal-oxide-semiconductor) capacitor structure. The leakage currents of engineered tunneling barriers (ONO, NON stacks) are lower than that of the conventional $SiO_2$ single layer at low electrical field. Meanwhile, the engineered tunneling barriers have larger tunneling current at high electrical field. Furthermore, the increased tunneling current through engineered tunneling barriers related to high speed operation can be achieved by annealing processes.

• Journal of the Korean Ceramic Society
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• v.49 no.2
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• pp.146-150
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• 2012

The effects of $Al_2O_3$ on the crystallization behavior of glass compositions in the $Na_2O$-CaO-$SiO_2$ system were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effect of $Al_2O_3$ content on the mechanical properties, density, phase formation, and microstructures of $Na_2O$-CaO-$P_2O_5$-$SiO_2$ glass ceramics were studied. The thermal parameters of each glass were studied by DTA. The density of the glass ceramic samples was measured by Archimedes' method. It was found that the glass-ceramic containing 2.0 molar percent $Al_2O_3$ had desirable sintering behavior and reached an acceptable density. Phase investigation and micro-structural analysis were performed by XRD and SEM, respectively.

• Journal of the Korean Ceramic Society
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• v.28 no.10
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• pp.803-809
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• 1991

Microstructure, room temperature resistivity and temperature coefficient of resistance of BaTiO3 ceramics were characterized and measured in this study. The basic composition of the BaTiO3 cremics was formed by adding 0.25 mol% Dy2O3 and 0.07 mol% MnO2 to the BaTiO3 composition. Samples of the BaTiO3 ceramics were prepared by adding various amounts of the TiO2, SiO2 and Al2O3 to the basic composition. An addition of 1 mol% TiO2, 2 mol% SiO2 and 0.5 mol% Al2O3 to the basic composition resulted both the values of the room temperature resistivity and the temperatured coefficient being maxium. Meanwhile, an addition of 1 mol% TiO2 and 1 mol% Al2O3 to the basic composition resulted the value of the room temperature resistivity maxium and the temperature coefficient minimum. The temperature coefficient showed a maximum value as well as a minimum value when the three kinds of the additives were added together to the basic composition of the BaTiO3 ceramics. Maxed phases of BaTi3O7, BaTiSiO5 and BaAl2Si2O8 were present at the grain boundary.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.5
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• pp.427-431
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• 2011

Hybrid $SiO_2-TiO_2$ photoelectrode with different type of layers was investigated in dye-sensitized solar cells (DSSC). Use of a thin layer of nanocrystalline $TiO_2$ would imply reduction in the amount of dye coverage, however, lower amount of dye in the thin films would imply fewer electron generation upon illumination. So, thus, it becomes necessary to include a $SiO_2-TiO_2$ layer for increase light harvesting effect such that the lower photon conversion due to thin layer could be compensated. In this paper reports the use of transparent high surface area $TiO_2$ layer and an additional $SiO_2-TiO_2$ layer, thus ensuring adequate light harvesting in these devices. The best solar conversion efficiency 6.6% under AM 1.5 was attained with a multi-layer structure using $TiO_2$ layer/$SiO_2-TiO_2$ layer/$TiO_2$ layer for the light harvesting and this had resulted to about 44% increase in photocurrent density of dye-sensitized solar cells.

• Korean Journal of Materials Research
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• v.5 no.3
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• pp.324-332
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• 1995

전자빔 증착법을 사용하여 Ti과 Co를 Si(100) 단결정, 다결정 Si 및 Si$O_{2}$기판에 증착한 후 90$0^{\circ}C$에서 20초 급속 열처리하여, Co/Ti 이중박막으로부터의 실리사이드화 반응을 조사하였다. 단결정 시편의 경우 Ti의 두께를 5~6mm로 최소화함으로서 두께가 균일하고 기판과의 계면이 평탄하며 비저항이 낮고 열적 안정성이 높은 Co$Si_{2}$ 에피박막을 형성할 수 있었다. 그러나 다결정 시편에는 두께와 계면이 불균일하고 열적으로도 불안정한 다결정의 Co$Si_{2}$와 그 위에 두개의 Co-Ti-Si혼합층이 형성되었다. 한편 Si$O_{2}$ 우에 증착된 Co/Ti은 열처리를 하여도 확산하지 않고 그대로 남아 있어서, Co/Ti 이중박막의 Si$O_{2}$와의 반응성이 미약함을 보여 주었다.