• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.805-810
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• 2012

Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. $SnO_2$ is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of $10^{-3}{\Omega}{\cdot}cm$ and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of $SnO_2$ were investigated. The addition of Y in $SnO_2$ was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of $SnO_2$. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of $SnO_2$ single-doped with Al and Y. $\{(x/2)Al_2O_3+(x/2)Y_2O_3\}-SnO_2$ was used for the source of Al and Y to prevent the evaporation of $Al_2O_3$ and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of $SnO_2$ co-doped with Al and Y will be discussed.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.33-39
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• 2010

Printing technologies have been indicated as alternative methods for patterning conductive, semi-conductive or insulative materials on account of their low-cost, large-area patternability and pattern flexibility. For application of the printing technologies in manufacture of semiconductor or display modules, ink or paste composed of nanoparticles, solvent and additives are basically needed. Here, we report recent advances in eco-friendly nano-ink technology for semiconductor and display technology. Then, we will introduce an eco-friendly ink formation technology developed in our group with an example of manufacturing $SiO_2$ nanopowders and inks. We tried to manufacture ultrafine $SiO_2$ nanoparticles by applying a low-temperature synthetic method, and then attempted to fabricate the printed $SiO_2$ film onto the glass substrate to see whether the $SiO_2$ nanoparticles are feasible for the printing or not. Finally, the electrical characteristics of the films were measured to investigate the effect of the manufacturing parameters.

• Journal of the Korean Magnetics Society
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• v.12 no.6
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• pp.231-234
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• 2002

Magnetic properties are investigated for top- and bottom-type spin valves of Si/SiO$_2$/NiO(60nm)/Co(2.5nm)/Cu(1.95nm)/Co(4.5nm)/NOL(t nm; Nano Oxide layer). The MR ratios of the bottom-type spin valves with NOL are larger than those of the top-type spin valves. However, the enhancement of the former is lower than the latter. Both of spin-valves also showed almost constant Ap and smaller p. Enhanced MR ratios of spin valves with NOL result mainly from small values of with constant Ap which due to specular diffusive electron scattering at NOL(NiO)/metal interfaces.

• Korean Journal of Metals and Materials
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• v.46 no.11
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• pp.762-769
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• 2008

Hydrogenated amorphous silicon(a-Si : H) layers, 120 nm and 50 nm in thickness, were deposited on 200 $nm-SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by E-beam evaporation. Finally, 30 nm-Ni/120 nm a-Si : H/200 $nm-SiO_2$/single-Si and 30 nm-Ni/50 nm a-Si:H/200 $nm-SiO_2$/single-Si were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 30 minute. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide on the 120 nm a-Si:H substrate showed high sheet resistance($470{\Omega}/{\Box}$) at T(temperature) < $450^{\circ}C$ and low sheet resistance ($70{\Omega}/{\Box}$) at T > $450^{\circ}C$. The high and low resistive regions contained ${\zeta}-Ni_2Si$ and NiSi, respectively. In case of microstructure showed mixed phase of nickel silicide and a-Si:H on the residual a-Si:H layer at T < $450^{\circ}C$ but no mixed phase and a residual a-Si:H layer at T > $450^{\circ}C$. The surface roughness matched the phase transformation according to the silicidation temperature. The nickel silicide on the 50 nm a-Si:H substrate had high sheet resistance(${\sim}1k{\Omega}/{\Box}$) at T < $400^{\circ}C$ and low sheet resistance ($100{\Omega}/{\Box}$) at T > $400^{\circ}C$. This was attributed to the formation of ${\delta}-Ni_2Si$ at T > $400^{\circ}C$ regardless of the siliciation temperature. An examination of the microstructure showed a region of nickel silicide at T < $400^{\circ}C$ that consisted of a mixed phase of nickel silicide and a-Si:H without a residual a-Si:H layer. The region at T > $400^{\circ}C$ showed crystalline nickel silicide without a mixed phase. The surface roughness remained constant regardless of the silicidation temperature. Our results suggest that a 50 nm a-Si:H nickel silicide layer is advantageous of the active layer of a thin film transistor(TFT) when applying a nano-thick layer with a constant sheet resistance, surface roughness, and ${\delta}-Ni_2Si$ temperatures > $400^{\circ}C$.

• Applied Microscopy
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• v.36 no.spc1
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• pp.25-33
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• 2006

Nanofabrication with finely focused ion and electron beams is reviewed, and position and size controlled fabrication of nano-metals and -semiconductors is demonstrated. A focused ion beam (FIB) interface attached to a column of 200keV transmission electron microscope (TEM) was developed. Parallel lines and dots arrays were patterned on GaAs, Si and $SiO_2$ substrates with a 25keV $Ga^+-FIB$ of 200nm beam diameter at room temperature. FIB nanofabrication to semiconductor specimens caused amorphization and Ga injection. For the electron beam induced chemical vapor deposition (EBI-CVD), we have discovered that nano-metal dots are formed depending upon the beam diameter and the exposure time when decomposable gases such as $W(CO)_6$ were introduced at the beam irradiated areas. The diameter of the dots was reduced to less than 2.0nm with the UHV-FE-TEM, while those were limited to about 15nm in diameter with the FE-SEM. Self-standing 3D nanostructures were also successfully fabricated.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.203-209
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• 1999

LaAlO3d single phase used as the butter layer on Si wafer for YBa2Cu3O7-$\delta$ superconductor application were prepared by solid state reaction method and by self-sustaining combustion process. The microstructure and crystallity of synthesiszed LaAlO3 powder studied using scanning electron microscope (SEM) and X-ray diffractometer(XRD), specific surface area and sintering characteristics fo powder were investigated by Brunauer-Emmett-Teller (BET) method and dilatometer respectively. In solid state reaction method, it is difficult to obtain LaAlO3 single phase up to 150$0^{\circ}C$ period. However, in self-sustaining combustion process, it is to easy to do it only $650^{\circ}C$. Based on the results of analysis of dilatometer it is easier to obtain high sintering density (98.87%) in self-sustaining combustion process than in the solid state reaction method. This reason is that the average particle size prepared by self-sustaining combustion process is nano crystal size and has high specific surface are value(56.54 $m^2$/g) compared with that by solid state reaction method. Also, LaAlO3 layer on the Si wafer has been achieved by screen printing and sintering method. Even though the sintering temperature is 130$0^{\circ}C$, the phenomena of silicon out diffusion in LaAlO3/Si interphase are not observed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.6 s.336
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• pp.17-22
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• 2005

Organic-inorganic hybrid type thin films are the next generation candidates as low-k materials. SiOC films are analyzed the bonding structure by the red and blue chemical shift using the fourier transform infraredspectra. Conventional chemical shift of organic chemistry is a red shift, but hybrid type SiOC films were observed the red and blue shift. The chemical shift originates from the interaction between the C-H bond and high electronegative atoms, and the blue shift in SiOC films is caused by the porosity due to the increase of the electron rich group such as much methyl radicals. The bonding structures of SiOC films are also divided into the Si-O-C cross-link structure and the Si-O-C cage-link structure due to the chemical shifts. The Si-O-C cross-link structure progressed the adhesion attributed to the C-H bond elongation in the reason of the red shift, and the dielectric constant also decreases.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.3
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• pp.9-17
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• 2011

Nano-composite solders have been studied to improve the properties of Pb-free solder joints. The nanoparticles in the composite solders were carbon nanotubes(CNTs), metals (Ag, Ni, Cr, etc.), ceramics (SiC, $ZrO_2$, $TiB_2$, etc.). To fabricate the nano-composite solders, mechanical mixing methods and in-situ fabrication method has been used for well-dispersed nano phase. The characteristic properties of the nano-composite solders were high creep resistance, low undercooling, low IMC growth rate and fine microstructures. More researches on the nano-composite solders are required to improve the processibility and the reliability of the nano-composite solder joints.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.481-484
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• 2005

Recently, Since the advanced nano technology develops unique physical and chemical properties different from those of the conventional materials. Normal concretes mixed with nano size materials have been studied to improve the fire-resistance with high strength and lower heat conductivity. In this pilot study, the nano-particle contents in the specimens ($\Phi$10\times20 cm$) were 0, 2, 4, and 6$\%$ by weight of cement, and fire-temperatures 800$^{circ}C$ was considered. The results show that as the nano-particle contents increases, fire resistance of concrete are superior to those of the ordinary concrete. Also, the experimental results show that fire resistance of nano Aluminum hydroxide dispersed concrete are superior to those of the nano-SiO2 concrete.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.456-461
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• 2017

In this study, the rheological properties of nitromethane gel propellants on nano/micron sized gelling agent are investigated. Silicon dioxide is used as the gellant with 5 wt%, 6.5 wt% and 8 wt% concentration, respectively, where the measurements are conducted under steady-state shear flow conditions using a rotational rheometer. The nitromethane/silicon dioxide gel showed non-Newtonian flow behavior for the entire experimental shear rate ranges. The gel fuels with nano-sized gellant had a slightly higher viscosity than the gel fuels with micron-sized one for low shear rate range. Additionally, it was found that Herschel-Bulkley model can hardly describe the rheological behavior of nitromethane gel propellant, but the NM model(by Teipel and Forter-Barth) is better suited to explain the rheological behavior of nitromethane gel propellant.