• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.8
• /
• pp.622-628
• /
• 2001

We developed 1- and 2-dimensional fluid model for the analysis of a capacitively coupled Ar RF(Radio Frequency) glow discharge. This discharge is in pure Ar gas at the pressure 100[mTorr], frequency 13.56[MHz] and voltage amplitude 120[V}. This model is based on the equations of continuity and electron energy conservation coupled with Poison equation. 2-dimensional model is simulated on the condition of GEC(Gaseous Electronic Conference cell). The geometry of the discharge chamber and the electrodes used in the model is cylindrically simmetric; tow cylinders for the electrodes are surrounded by the grounded chamber. It is shown that 1-dimensional model is very useful on the understanding of RF glow discharge property and of the movement of charged particles. 2-dimensional model predicts off-axis maximum structure as in the experiments and has the results in qualitatively and quantitatively good agreement with the experiments. Effects of dc self-bias voltage, guard ring and reactor geometry is discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.11a
• /
• pp.121-124
• /
• 1996

It is well known that the metallo- phthalocyanine (MPcs) are sensitive to toxic gaseous molecules such as NO$_2$and also chemically and thermally stable. Therefore, lots of MPcs have been studied for the potential chemical sensor for NO$_2$gas using quartz crystal microbalance(QCM) or electrical conductivity. In this study, thin films of octa(2-ethylhexyloxy) copper-phthalocyanine were prepared by Langmuir -Blodgett method and characterized by using UV-VIS spectroscopy and ellipsometry. Transfer condition, and characterization of LB films were investigated and preliminary results of current-voltage(I-V) characteristics of these films exposed to NO$_2$gas as a function of film thickness, temperature and temperature were discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.11a
• /
• pp.147-151
• /
• 1996

Brewster angle microscopy(BAM) makes it possible to observe the monolayer states on the water subphase and the phase transitions from a gaseous phase via a expanded phase to a condensed phase. Also BAM can be used to observe the films on the solid substrate such as Langmuir-Blodgett(LB) films. In this Paper Polyamic Acid Alkylamine Salts(PAAS) was used for forming L films and LB films and $\pi$-A isotherm showed pressure of each phase. We obtained BAM images as surface pressure increased. Images of LB films were compared with data from ellipsometry which was used to measure the film thickness. Images of both L films and LB films were analyzed with computer in the point of brightness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.11a
• /
• pp.492-494
• /
• 2002

The fundamental principles of the operation of microwave discharges that are used to convert microwave energy to broad spectrum visual light are known. In this paper, emission dependance of microwave discharges in mixture content of sulfur with noble gases was studied. It is shown that the excitation of this gaseous mixture is carried out in two phases: (1) ionization of noble gas atoms by a microwave field and (2) the consequent maintenance of slightly ionized nonequilibrium plasma by the field. These two processes have essentially various thresholds for the microwave pump. The purpose of this work is to investigate spectral properties of the high frequency discharges in a mixture sulfur vapors with noble gases.

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1247-1249
• /
• 1997

Langmuir-Blodgett(LB) method is one of the ways of fabricating organic ultra thin films. It is well known that It has the advantage to control the alignment and orientation of the molecules in the films. Metallo-phthalocyanines (MPcs) are sensitive to electron affinitive toxic gaseous molecules, such as $NO_2$, NO, $SO_2$. In this study, thin films of octa-dodecyloxy copper-phthalocyanine were prepared by LB method and characterized by using UV/Vis absorption spectroscopy and ellipsometry. Optimal transfer condition of LB films was investigated and preliminary results of current-voltage (I-V) characteristics of these films exposed to $NO_2$ gas as a function of film thickness.

• Carbon letters
• /
• v.1 no.1
• /
• pp.12-16
• /
• 2000

Carbon fiber was reacted with gaseous silicon monoxide which is produced from pack-powder mixture at elevated temperature. As a result of the reaction, two kinds of SiC fiber were obtained. The first one was SiC fibers which were converted from carbon fiber. The fiber is constituted with polycrystal like fine grains or monolithic crystals that have a size from sub-micron to $10\;{\mu}m$. Their size depends on the temperature during the conversion reaction. The second one was ultra-fine SiC fibers that were found on the surface of the converted SiC fibers. The ultra-fine fibers have diameters from 0.08 to $0.2\;{\mu}m$ and their aspect ratio were larger than 100. The chemical composit ion of the ultra-fine fibers was analyzed using an Auger electron spectroscopy. In result, the fibers consist of 51% silicon, 38% carbon and 11% oxygen by weight.

• Journal of the Korean Ceramic Society
• /
• v.35 no.12
• /
• pp.1249-1256
• /
• 1998

${\beta}$-Silicon carbide(${\beta}$-SiC) whiskers could be synthesized by the carbothermal reduction of kaolin at tem-peratures between 1400 and 1500$^{\circ}C$. The whiskers were grown up to about 1150 of aspect ratio by VS mechanism (showing tapering tips) and to about 45 of that by VLS mechanism (showing round droplet tips) respectively. Hydrocarbon like methane in the reaction atmosphere promoted the formation of gaseous il-icon monoxide(SiO) from silicon dioxide(SiO2) and subsequently reacted with it to form whiskers. The for-mation of ${\beta}$-SiC whiskers increased with increasing carbon content(to 30 wt%) and reaction temperatures. The max. yield of ${\beta}$-SiC whiskers was 15% at 1500$^{\circ}C$ under 20%CH4/80%H2.

• The Journal of Natural Sciences
• /
• v.8 no.2
• /
• pp.129-136
• /
• 1996

The direct conversion of solid potassium chloride to solid potassium nitrate by the reaction of the chloride with gaseous nitrogen dioxide is suggested for the preparation of potassium nitrate. Thermodynamic calculations indicate that the free energy change is favorable at ordinary temperatures and that the reaction is exothermic. Experiments are described in which it was found that the reaction takes place at ordinary temperatures in the presence of a small amount of water with good yield. Nitrosyl chloride is produced simultaneously.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.474-474
• /
• 2011

Graphene is considered as a potential candidate for the key material in the ideal 2D nanoelectronics. Recently, it is reported that graphene has an interesting sensitivity to molecular adsorption on it. Such properties are believed to be enhanced by the existence of disorders and ripples inside graphene as well as by the interaction with the substrate underneath. Here, we report the effect of introducing structural disorders to the graphene on its electrical properties such as conductance, transconductance, low frequency noise, which can be successfully described by a simple model of the continuum percolation. In addition, the response of the graphene device to gaseous molecular adsorption was systematically investigated and the results were discussed along with the change in Raman spectra.

• Journal of the Korean Chemical Society
• /
• v.7 no.2
• /
• pp.106-114
• /
• 1963

The products from polymer pyrolysis at $450^{\circ}$ are cooled with ice, then liquid and gaseous portions are analysed by gas chromatography. Di-2-ethyl hexyl sebacate column, silicone oil column, silica gel column and tetraethyleneglycol dimethylether column, which was most effective for the separation of hydrocarbon gases, are used. Identification of isomers could be secured more effectively by gas chromatography than mass spectrometry. Elucidation of the mechanism for thermal decomposition of polymers could be done through the identification of pyrolysis products. Although more extensive work is needed, some patterns of polymer pyrolysis are discussed.