• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.89-94
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• 2011

The cause of the thickness non-uniformity in the large area deposition of $SiO_2$ films by PECVD(Plasma Enhanced Chemical Vapor Deposition) was investigated by the plasma diagnostics. The spatial distribution of the plasma species in the chamber was obtained with DLP(Double Langmuir Probe) and the new-designed probe-type QMS(Quadrupole Mass Spectrometer). From the relationship between the spatial distribution of the plasma species and the depositing rate of the $SiO_2$ films, it was conformed that the non-uniform deposition of $SiO_2$ films was related with the spatial distribution of the oxygen radical density and electron temperature.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2373-2385
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• 1995

The goals of this study are to apply exciplex method to the visualization of the fuel spray of a diesel engine and to investigate the liquid phase of fuel spray that injected at the various tips of a fuel injector. This study provides the informations for the improvement of the diesel injection system and the structures of diesel spry with the boiling of fuel droplets in combustion chamber by the exciplex method. Hexame was used as fuel for approximation to injection condition of the engine. And naphthalene and TMDP were added to the fuel for the visualization by exciplex method. Experimental injectors were 4hole, 8hole, and 1hole impinging injectors. In the injection condition of actual engine the exciplex was sufficient to catch the liquid phase signal. The spray penetration of impinging injector was small than that of actual 4 and 8hole injector but atomization was better. The upper bound of impinging injector was determined by the geometry of a cylinder head and the lower bound was determined by spray angle. On impinging injector the atomization was better at the edge of disk than at center of disk and also the mixing with environmental gas was better.

• International Journal of Automotive Technology
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• v.5 no.3
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• pp.155-164
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• 2004

The direct injection gasoline spray-wall interaction was characterized inside a heated pressurized chamber using various visualization techniques, including high-speed laser-sheet macroscopic and microscopic movies up to 25,000 frames per second, shadowgraph, and double-spark particle image velocimetry. Two hollow cone high-pressure swirl injectors having different cone angles were used to inject gasoline onto a heated plate at two different impingement angles. Based on the visualization results, the overall transient spray impingement structure, fuel film formation, and preliminary droplet size and velocity were analyzed. The results show that upward spray vortex inside the spray is more obvious at elevated temperature condition, particularly for the wide-cone-angle injector, due to the vaporization of small droplets and decreased air density. Film build-up on the surface is clearly observed at both ambient and elevated temperature, especially for narrow cone spray. Vapor phase appears at both ambient and elevated temperature conditions, particularly in the toroidal vortex and impingement plume. More rapid impingement and faster horizontal spread after impingement are observed for elevated temperature conditions. Droplet rebounding and film break-up are clearly observed. Post-impingement droplets are significantly smaller than pre-impingement droplets with a more horizontal velocity component regardless of the wall temperature and impingement angle condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.632-635
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• 2001

Microcrystalline Si films have been deposited by using five W-wire filaments of 0.5 mm diameter for hot-wire chemical vapor deposition (HWCVD). We compared the HWCVD grown films with the film exposed to transformer couple plasma system for the modification of seed layer. W-wire filament temperature was maintained below 1600$^{\circ}C$ to avoid metal contamination by thermal evaporation at the filament. Deposition conditions were varied with H$_2$dilution ratio, with and without plasma treatment. From the Raman spectra analysis, we observed that the film crystallization was strongly influenced by the H$_2$dilution ratio and weakly depended on the distance between the wire and a substrate. We were able to achieve the crystalline volume fraction of about 70% with an SiH$_4$/H$_2$ratio of 1.3%, a wire temperature of 1514$^{\circ}C$, a substrate separation distance of 4cm, and a chamber pressure of 38 mTorr. We investigated the influence of ${\mu}$c-Si film properties by using a plasma treatment. This article also deals with the influence of the H$_2$dilution ratio in crystallization modification.

• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.1-4
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• 2015

Production of $MgB_2$ film on metallic Hastelloy with SiC as the buffer layer was achieved by means of hybrid physical-chemical vapor deposition technique, whereas SiC buffer layers with varied thickness of 170 and 250 nm were fabricated inside a pulsed laser deposition chamber. Superconducting transition temperature and critical current density were verified by transport and magnetic measurement, respectively. With SiC buffer layer, the reduced delaminated area at the interface of $MgB_2$-Hastelloy and the slightly increased $T_c$ of $MgB_2$ tapes were clearly noticed. It was found that the upper critical field, the irreversibility field and the critical current density were reduced when $MgB_2$ tapes were buffered with SiC buffer layer. Clarifying the mechanism of SiC buffer layer in $MgB_2$ tape in affecting the superconducting properties is considerably important for practical applications.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.271-284
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• 1999

As a semiconductor material for electronic devices operated under extreme environmental conditions, silicon carbides (SiCs) have been intensively studied because of their excellent electrical, thermal and other physical properties. The growth characteristics of single-crystalline 4H-SiC homoepitaxial layers grown by a thermal chemical vapor deposition (CVD) were investigated. Especially, the successful growth condition of 4H-SiC homoepitaxial layers using a SiC-uncoated graphite susceptor that utilized Mo-plates was obtained. The CVD growth was performed in an RF-induction heated atmospheric pressure chamber and carried out using off-oriented substrates prepared by a modified Lely method. In order to investigate the crystallinity of grown epilayers, Nomarski optical microscopy, Raman spectroscopy, photoluminescence(PL), scanning electron microscopy (SEM) and other techniques were utilized. The best quality of 4H-SiC homoepitaxial layers was observed in conditions of growth temperature 1500$^{\circ}C$ and C/Si flow ratio 2.0 of C3H3 0.2sccm & SiH4 0.3sccm. The growth rate of epilayers was about 1.0$\mu\textrm{m}$/h in the above growth condition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.71-74
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• 2006

In this paper, we investigated the characterization of silicon oxide(SiOx) thin film on Ethylene Terephthalate(PET) substrates by e-beam deposition for transparent barrier application. The temperature of chamber increases from $30^{\circ}C$ to $110^{\circ}C$, the roughness increase while the Water vapor transmission rate (WVTR) decreases. Under these conditions, the WVTR for PET can be reduced from a level of $0.57 g/m^2/day$ (bare subtrate) to $0.05 g/m^2/day$ after application of a 200-nm-thick $SiO_2$ coating at 110 C. A more efficient way to improve permeation of PET was carried out by using a double side coating of a 5-${\mu}m$-thick parylene film. It was found that the WVTR can be reduced to a level of $-0.2 g/m^2/day$. The double side parylene coating on PET could contribute to the lower stress of oxide film, which greatly improves the WVTR data. These results indicates that the $SiO_2$ /Parylene/PET barrier coatings have high potential for flexible organic light-emitting diode(OLED) applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.387-390
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• 2002

This paper presents deposition and characterizations of microcrystalline silicon(${\mu}$c-Si:H) films prepared by hot wire chemical vapor deposition at substrate temperature below 300$^{\circ}C$. The SiH$_4$ concentration[F(SiH$_4$)/F(SiH$_4$).+(H$_2$)] is critical parameter for the formation of Si films with microcrystalline phase. At 6% of silane concentration, deposited intrinsic ${\mu}$c-Si:H films shows sufficiently low dark conductivity and high photo sensitivity for solar cell applications. P-type ${\mu}$c-S:H films deposited by Hot-Wire CVD also shows good electrical properties by varying the rate of B$_2$H$\_$6/ to SiH$_4$ gas. The solar cells with structure of Al/nip ${\mu}$c-Si:H/TCO/g1ass was fabricated with single chamber Hot-Wire CVD. About 3% solar efficiency was obtained and applicability of HWCVD for thin film solar cells was proven in this research.

• Electrical & Electronic Materials
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• v.8 no.1
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• pp.90-94
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• 1995

Reactive Ion Etching(RIE) of Si$_{3}$N$_{4}$ in a CF$_{4}$/O$_{2}$ gas plasma exhibits such good anisotropic etching properties that it is widely employed in current VLSI technology. However, the RIE process can cause serious damage to the silicon surface under the Si$_{3}$N$_{4}$ layer. When an atmospheric pressure chemical vapor deposited(APCVD) SiO$_{2}$ layer is used as a etch-stop material for Si$_{3}$N$_{4}$, it seems inevitable to get a good etch selectivity of Si$_{3}$N$_{4}$ with respect to SiO$_{2}$. Therefore, we have undertaken thorough study of the dependence of the etch rate of Si$_{3}$N$_{4}$ plasmas on $O_{2}$ dilution, RF power, and chamber pressure. The etch selectivity of Si$_{3}$N$_{4}$ with respect to SiO$_{2}$ has been obtained its value of 2.13 at the RF power of 150 W and the pressure of 110 mTorr in CF$_{4}$ gas plasma diluted with 25% $O_{2}$ by flow rate.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1067-1072
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• 2009

In vapor compression systems which use refrigerant as a working fluid, the oil is commonly used for compressor lubrication. Since the presence of lubrication oil can change the characteristics properties of refrigerant, the oil affects the heat transfer performance of heat exchanger to a large extent. In this paper, we focus on the effect of PVE oil experimentally on heat transfer performance of the fin-tube heat exchangers which use R410A as a refrigerant. To evaluate the heat transfer performance, the refrigerant to air type test facility chamber has been used. Fin-tube heat exchanger with grooved has been tested while according to the oil mass fraction variation from nearly zero to 1.7 wt%. It was found that the low level of oil mass fraction has an obvious effect on heat transfer performance, while the high level seems no significant influence. The influence of the oil mass fraction to heat transfer performance, however, is different between evaporation and condensation.