• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.19.2-19.2
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• 2010

Printed electronics using printing process has broadened in all respects such as electrics (lighting, batteries, solar cells etc) as well as electronics (OLED, LCD, E-paper, transistor etc). Copper is considered to be a promising alternative to silver for printed electronics, due to very high conductivity at a low price. However, Copper is easily oxidized, and its oxide is non-conductive. This is the highest hurdle for making copper inks, since the heat and humidity that occurs during ink making and printing simply accelerates the oxidation process. A variety of chemical treatments including organic capping agents and metallic coating have been used to slow this oxidation. We have established synthetic conditions of copper nanoparticles (CuNPs) which are resistant to oxidation and average diameter of 20 to 50nm. Specific resistivity should be less than $4\;{\mu}{\Omega}{\cdot}cm$ when sintered at lower temperature than $250^{\circ}C$ to be able to apply to conductive patterns of FPCBs using ink-jet printing. Through this study, the parameters to control average diameter of CuNPs were found to be the introduction of additive agent, the feeding rate of reducing agent, and reaction temperature. The CuNPs with various average diameters (58, 40, 26, 20nm) could be synthesized by controlling these parameters. The dispersed solution of CuNPs with an average size of 20 nm was made with nonpolar solvent containing 3 wt% of binder, and then coated onto glass substrate. After sintering the coated substrates at $250^{\circ}C$ for 30 minutes in nitrogen atmosphere, metallic copper film resulted in a specific resistivity of $4.2\;{\mu}{\Omega}{\cdot}cm$.

• Journal of the Korean institute of surface engineering
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• v.38 no.5
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• pp.188-192
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• 2005

Indium zinc oxide (IZO) thin films were deposited on glass substrate by dc magnetron sputtering. The effects of oxygen flow rate and deposition temperature on electrical and optical properties of the films were investigated. With addition of small amount of oxygen gas, the characteristic properties of amorphous IZO films were improved and the specific resistivity was about $4.8{\times}10^{-4}\Omega{\cdot}cm$. Change of structural properties according to the deposition temperature was observed with XRD, SEM, and AFM. Films deposited above $300^{\circ}C$ were found to be polycrystalline. Surface roughness of the films was increased due to the formation of grains on the surface. Electrical conductivity became deteriorated for polycrystalline IZO films. Consequently, high quality IZO films could be prepared by do sputtering with $O_{2}/Ar{\simeq}0.03$ and deposition temperature in range of $150\~200^{\circ}C$; a specific resistivity of $3.4{\times}10^{-4}{\Omega}{\cdot}cm$, an optical transmission over $90\%$ at wavelength of 550 nm, and a rms value of surface roughness about $3{\AA}$.

• Macromolecular Research
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• v.12 no.4
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• pp.399-406
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• 2004

Glass-like carbon precursors shrink significantly during curing and carbonization, which leads to crack formation and bending. Cured furan resin powder and ethanol were added to furan resin to diminish the weight loss, to suppress the shrinkage and bending, and to readily release the gases evolved during polymerization and curing. Curing and carbonization were controlled by pressure and slow heating to avoid damage to the samples. The effect of the filler and ethanol on the fabrication process was examined by measuring the properties of the glass-like carbon, such as the specific gravity, bending strength, electrical resistivity, and microstructural change. The specific gravities of the filler-added glass-like carbons were higher than those of the ethanol-added samples because of the formation of macropores from the vaporization of ethanol during the curing and polymerization processes. Although the ethanol-added glass-like carbons exhibited lower bending strengths after carbonization than did the filler-added samples, the opposite result was observed after aging at 2,600$^{\circ}C$. We found that the macropores created from ethanol were contracted and removed upon heat treatment. The electrical resistivity of the glass-like carbon aged at 2,600$^{\circ}C$ was lower than those of the samples carbonized at 1,000$^{\circ}C$. We attribute this phenomenon to the fact that aging at high temperature led to well-developed microstructures, the removal of macropores, and the reduction of the surface area.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.717-723
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• 2009

Ni/Al ('/' denotes deposition sequence) contacts were deposited on Al-implanted 4H-SiC for ohmic contact formation, and the conduction properties were characterized and compared with those of Ni-only contacts. The thicknesses of the Ni and Al thin film were 30 nm and 300 nm, respectively, and the films were sequentially deposited bye-beam evaporation without vacuum breaking. Rapid thermal anneal (RTA) temperature was varied as follows : $840^{\circ}C$, $890^{\circ}C$, and $940^{\circ}C$. The specific contact resistivity of the Ni contact was about $^{\sim}2\;{\pm}\;10^{-2}\;{\Omega}{\cdot}cm^2$, However, with the addition of Al overlayer, the specific contact resistivity decreased to about $^{\sim}2\;{\pm}\;10^{-4}\;{\Omega}{\cdot}cm^2$, almost irrespective of RTA temperature. X-ray diffraction (XRD) analysis of the Ni contact confirmed the existence of various Ni silicide phases, while the results of Ni/Al contact samples revealed that Al-contaning phases such as $Al_3Ni$, $Al_3Ni_2$, $Al_4Ni_3$, and $Ab_{3.21}Si_{0.47}$ were additionally formed as well as the Ni silicide phases. Energy dispersive spectroscopy (EDS) spectrum showed interfacial reaction zone mainly consisting of Al and Si at the contact interface, and it was also shown that considerable amounts of Si and C have diffused toward the surface. This indicates that contact resistance lowering of the Ni/Al contacts is related with the formation of the formation of interfacial reaction zone containing Al and Si. From these results, possible mechanisms of contact resistance lowering by the addition of Al were discussed.

• Journal of Radiation Protection and Research
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• v.16 no.2
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• pp.1-6
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• 1991

The $HgI_2$ single crystal which can be used for the ${\gamma}-ray$ detector at room temperature was grown by Temperature Oscillation Method. The low temperature photoluminescence, specific resistivity and trap concentration of $HgI_2$ single crystal were investigated. Three main luminescence bands were observed at 2.30eV, 2.20eV and 2.00eV at 20K, related to the excitons, I-vacancies and impurities, respectively. The specific resistivity and trap concentration of $HgI_2$ single crystal were $10^{11}{\Omega}\;cm\;and\;1.8{\times}10^{14}/cm^3$ at room temperature, respectively. Also the radiation detecting system was deviced by $HgI_2$ ${\gamma}-ray$ detector, one chip microprocessor, LCD module and personal computer. The prepared $HgI_2$ ${\gamma}-ray$ detector showed a good linearity of ${\gamma}-radiation$ dose for standard ${\gamma}-ray$.

• Journal of the Korean institute of surface engineering
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• v.49 no.1
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• pp.54-61
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• 2016

Screen printing of commercially available Ag paste is the most widely used method for the front side metallization of Si solar cells. However, the metallization using Ag paste is expensive and needs high temperature annealing for reliable contact. Among many metallization schemes, Ni/Cu/Sn plating is one of the most promising methods due to low contact resistance and mass production, resulting in high efficiency and low production cost. Ni layer serves as a barrier which would prevent copper atoms from diffusion into the silicon substrate. However, Ni based schemes by electroless deposition usually have low thermal stability, and require high annealing process due to phosphorus content in the Ni based films. These problems can be resolved by adding W element in Ni-based film. In this study, Ni-W-P alloys were formed by electroless plating and properties of it such as sheet resistance, resistivity, specific contact resistivity, crystallinity, and morphology were investigated before and after annealing process by means of transmission line method (TLM), 4-point probe, X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.764-768
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• 2002

Characteristics of ohmic Co/Si/Co contacts to n-type 4H-SiC are investigated systematically. The ohmic contacts were formed by annealing Co/Si/Co sputtered sequentially. The annealings were performed at $800^{\circ}C$ using RTP in vacuum ambient and $Ar:H_2$(9:1) ambient, respectively. The specific contact resistivity$(\rho_c)$, sheet resistance$(R_s)$, contact resistance$(R_c)$, transfer length$(L_T)$ were calculated from resistance$(R_T)$ versus contact spacing(d) measurements obtained from TLM(transmission line method) structure. While the resulting measurement values of sample annealed at vacuum ambient were $\rho_c=1.0{\tiimes}10^{-5}{\Omega}cm^2$, $R_c=20{\Omega}$ and $L_T$ = 6.0 those of sample annealed at $Ar:H_2$(9:1) ambient were $\rho_c=4.0{\tiimes}10^{-6}{\Omega}cm^2$, $R_c=4.0{\Omega}$ and $L_T$ = 2.0. The physical properties of contacts were examined using XRD and AES. The results showed that cobalt silicide was formed on SiC and Co was migrated into SiC.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1169-1177
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• 1995

Barium nitrate and yittrium nitrate were dissolved into distilled water. Titaium hydroxide precipitated from titanium chloride with NH4OH was dissolved into nitric acid. Each aqueous solution was mixed for 12 hr in the composition of Ba1-xYxTiO3 (x=0.1∼0.6) and the concentration of mixed solution was 0.1 mol/ι. The mixed solution was sprayed with an ultrasonic atomizer and carried into an electric furnace which was kept at 900∼1000$^{\circ}C$ and pyrolyzed. Pyrolyzed powders were collected on the glass filter with vacuum pump. Aqueous Mn solutiion was added into the synthesized powders, mixed with ultrasonic vibration and sintered at 1300∼1400$^{\circ}C$. Synthesized powders were characterized with SEM, XRD, DT-TGA, and BET. Microsture and resistivity of sintered body were investigated with SEM and multimeter. The results of this experiment were as follows; 1) Yittrium dooped BaTiO3 powders were synthesized above 950$^{\circ}C$. 2) The average particle sizes of powders from BET specific surface area and SEM were 0.045$\mu\textrm{m}$, 0.046$\mu\textrm{m}$ respectively. The particle size distribution was narrow in the range of 0.1∼1.0$\mu\textrm{m}$ from SEM. 3) Room temperature resistivity and pmax/pmin of 0.4 mol% Y doped specimen which was sintered at 1375$^{\circ}C$ were 102∼3 (Ω$.$cm) and 102∼3 respectively. 4) Room temperature resistivity and pmax/pmin of 0.4 mol% Y and 0.04 at% Mn added specimen which was sintered at 1375$^{\circ}C$ were 102∼3 (Ω$.$cm) and 106∼7 respectively. 5) Grain growth was inhibited with addition of Y2O3 and enhanced in addition of Mn by 0.05 atm%.

• Journal of the Korean Geotechnical Society
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• v.37 no.3
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• pp.5-17
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• 2021

This study aims to investigate the causes and countermeasures for the occurrence of tension cracks in the slope of the rock mass of heavy equipment for road construction. Electric resistivity survey was performed to investigate the expandable tensile crack range. As a result of examining the distribution of soft zones in the rock mass, a low specific resistance zone was found at the bottom of the access road where tensile cracks occurred. It was confirmed that a low resistivity zone was distributed near the top of the excavation slope. Therefore, reinforcements was performed by determining the location of the possible tensile crack as the top of the excavation slope. Two rows of reinforced piles and anchors were proposed as a reinforcement method, and the slope stability analysis showed that the allowable safety factor was satisfied after reinforcements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.605-608
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• 2001

Molybdenum disilicide is widely used for manufacturing high-temperature heating elements owing to its low electrical resistivity, good thermal conductivity, and ability to withstand oxidation at high temperatures. MoSi$_2$heating elements with 4-5wt% of montmorillonite type bentonite as plasticzer and a small amount of Si$_3$N$_4$, ThO$_2$, and B as additives was manufactured. Extruded rods of 3.7mmø and 6.7mmø diameter and 400mm long were fabricated using a vacuum extruder, which were then sinrered for 4-5 hrs. at the max. temperrature of 140$0^{\circ}C$. After 10 minute's oxidation treatment, the diameter of the rod is reduced. The heating elements thus prepared was stable at 1$700^{\circ}C$ and the physical properties such as specific electrical resistivity, hardness, apparent densisty, thermal expansion coefficient, and bending strength were almost identical with thoes of commercial heating elements. In this study we have tried to gain the practical knowledge of manufacturing MoSi$_2$heating elements so that it may be utilized later in a research of pilot scale and eventually be transferred to industry.