• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.4
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• pp.160-168
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• 2004

We investigate the effects of solutal convection on the crystal growth rate in a horizontal configuration for diffusive-convection conditions and purely diffusion conditions achievable in a low gravity environment for a nonlinear thermal gradient. It is concluded that the solutally-driven convection due to the disparity in the molecular weights of the component A $(Hg_2Br_2)$ and B (CO) is stronger than thermally-driven convection for both the nonlinear and the linear thermal profiles, corresponding to $Gr_t= 8.5{\times}10^3,\; Gr_s = 1.05{\times}10^5$. For both solutal and thermal convection processes, the growth rates for the linear thermal profile (conducting walls) are greater than for the nonlinear case. With the temperature humps, there are found to be observed in undersaturation for diffusive-convection processes ranging from $D_{AB}$ = 0.087 to 0.87. For the vertical configurations, the diffusion mode is so much dominated that the growth rate and interfacial distribution is nearly regardless of the gravitational accelerations. Also, the diffusion mode is predominant over the convection for the gravity levels less than 0.1 $g_0$ for the horizontally oriented configuration.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.387-387
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• 1998

This paper reports on a thermodynamic analysis for the GaN thick film growth by vapor phaseepitaxy method. The thermodynamic calculation was performed using a chemical stoichiometric algorism. Thesimulation variables include the growth temperature in a range 400~1500 K, the gas ratios $(GaCl_3)/(GaCl_3+NH_3)$and $(N_2)/(GaCl_3+NH_3)$. The theoretical calculation predicts that the growth temperature of GaN be in thelower range of 450~750 K than the experimental results. The difference in the growth temperature betweenthe simulation and the experiments indicates that the vapor phase epitaxy of GaN is kinetically limited,presumably, due to the high activation energy of thin film growth.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.388-395
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• 1998

This paper reports on a thermodynamic analysis for the GaN thick film growth by vapor phase epitaxy method. The thermodynamic calculation was performed using a chemical stoichiometric algorism. The simulation variables include the growth temperature in a range 400~1500 K, the gas ratios $(GaCl_3)/(GaCl_3+NH_3)$ and $(N_2)/(GaCl_3+NH_3)$. The theoretical calculation predicts that the growth temperature of GaN be in the lower range of 450~750 K than the experimental results. The difference in the growth temperature between the simulation and the experiments indicates that the vapor phase epitaxy of GaN is kinetically limited, presumably, due to the high activation energy of thin film growth.

• Journal of the Korean Vacuum Society
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• v.12 no.1
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• pp.70-77
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• 2003

It is well Down that the growth of carbon nanotubes (CNTs) by chemical vapor deposition (CVD) using a transition metal catalyst is greatly enhanced in a nitrogen environment. We show here that the enhanced growth is closely related to the activated nitrogen and it's incorporation into the CNT wall and cap during growth. This behavior is consistent with theoretical calculations of CNx thin films, showing that nitrogen incorporation to the graphitic basal plane reduces the elastic strain energy for curving the graphitic layer. Enhanced CNT growth by nitrogen incorporation is thus due to a decrease in the activation energies required for nucleation and growth of the tubular graphitic layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.210-210
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• 2000

Vertically well aligned multi-wall carbon nanotubes (CNT) were grown on nickel coated glass substrates by plasma enhanced hot filament chemical vapor deposition at low temperatures below 600$^{\circ}C$. Acetylene and ammonia gas were used as the carbon source and a catalyst. Effects of growth parameters such as pre-treatment of substrate, plasma intensity, filament current, imput gas flow rate, gas composition, substrate temperature and different substrates on the growth characteristics of CNT were systematically investigated. Figure 1 shows SEM image of CNT grown on Ni coated glass substrate. Diameter of nanotube was 30 to 100nm depending on the growth condition. The diameter of CNT decreased and density of CNT increased as NH3 etching time etching time increased. Plasma intensity was found to be the most critical parameter to determine the growth of CNT. CNT was not grown at the plasma intensity lower than 500V. Growth of CNT without filament current was observed. Raman spectroscopy showed the C-C tangential stretching mode at 1592 cm1 as well as D line at 1366 cm-1. From the microanalysis using HRTEM, nickel cap was observed on the top of the grown CNT and very thin carbon amorphous layer of 5nm was found on the nickel cap. Current-voltage characteristics using STM showed about 34nA of current at the applied voltage of 1 volt. Electron emission from the vertically well aligned CNT was obtained using phosphor anode with onset electric field of 1.5C/um.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.2
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• pp.125-132
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• 2008

The bubble dynamics and heat transfer associated with nucleate boiling in parallel microchannels is studied numerically by solving the equations governing conservation of mass, momentum and energy in the liquid and vapor phases. The liquid-vapor interface is tracked by a level set method which is modified to include the effects of phase change at the interface and contact angle at the wall. Also, the reversible flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of contact angle, wall superheat and the number of channels on the bubble growth and reversible flow are quantified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.996-1003
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• 2004

The bubble motion during nucleate boiling in a microchannel is investigated by numerically solving the equations governing conservation of mass, momentum and energy in the liquid and vapor phases. The liquid-vapor interface is tracked by a level set method which is modified to include the effects of phase change at the interface and contact angle at the wall. Also, the evaporative heat flux from the thin liquid film that forms underneath a growing bubble attached to the wall is incorporated in the analysis. Based on the numerical results, the effects of channel size, contact angle, wall superheat and waiting period on the bubble growth and heat transfer in a microchannel are quantified.

• Journal of Sensor Science and Technology
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• v.22 no.3
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• pp.175-180
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• 2013

This paper describes the characteristics of cubic silicon carbide (3C-SiC) films grown on a carbonized Si(100) substrate, using hexamethyldisilane (HMDS, $Si_2(CH_3)_6$) as a safe organosilane single precursor in a nonflammable $H_2$/Ar ($H_2$ in Ar) mixture carrier gas by atmospheric pressure chemical vapor deposition (APCVD) at $1280^{\circ}C$. The growth process was performed under various conditions to determine the optimized growth and carbonization condition. Under the optimized condition, grown film has a single crystalline 3C-SiC with well crystallinity, small voids, low residual stress, low carrier concentration, and low RMS. Therefore, the 3C-SiC film on the carbonized Si (100) substrate is suitable to power device and MEMS fields.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.914-917
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• 2002

Fabrication of micro carbon structures and patterns using laser-assisted chemical vapor deposition is studied. Argon ion laser and ethylene were used to grow micro carbon rod through pyrolytic decomposition of the reaction gas. The influence of reaction gas pressure and incident laser power on the diameter and growth rate of the micro carbon rod was experimentally investigated. The diameter of micro carbon rods increases linearly with respect to the laser power but is almost independent of the reaction gas pressure. Growth rate of the rod changes little with gas pressure when the laser power remains below 1W. When the carbon rod was grown at near threshold laser power, a very smooth surface is obtained on the rod. By continuously moving the focusing lens in the direction of growth, a micro carbon rod with a diameter of 28 ${\mu}{\textrm}{m}$ and aspect ratio of 100 was fabricated.

• Korean Journal of Crystallography
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• v.3 no.1
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• pp.53-66
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• 1992

Extensive research has been perform성 on the property-microstructure-process condition relations of thin films. The various proposed models are mainly based on physical vapor deposition processes. Especially the study on the surface condition of substrates in Zone 1 with low surface mobility has not been sufficient. In this study, therefore, we discussed the mochological changes of TiN films deposited by plusma enhanced chemical vapor deposition process with substrates of different composition and micro-rorghness, and compared it with the Structure Zone Model. We could find out that the growth rate of films increased and micro-grain size decreased with the increase in micro-roughness, but it does not improve the mechanical properties because of many imperfections like voids, micro-cracks, stacking faults, etc. This means that, in these deposition conditions, the increase in shadowing diffect is more effective than the increase in nucleation sites on the growth of films due to the increase in substrate roughness.