• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.213-217
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• 2012

Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases under thermal chemical vapor deposition system. By the incorporation of $SF_6$ additive in cyclic modulation manner, the dominant formation of the nanosized carbon coils could be achieved with maintaining the minimized sulfur additive amount. The geometry variation of the as-grown carbon coils, such as linear type, microsized coil type, wavelike nanosized coil type, and nanosized coil type, were investigated according to the different cyclic modulation manner of $SF_6$ flow. $SF_6$ gas incorporation develops the coil-type geometry. Furthermore, the higher flow rate of $SF_6$ gas increased the amount of the nanosized carbon coils. The slightly increased etching ability by $SF_6$ addition seems to be the cause for these results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.5
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• pp.211-214
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• 2004

Carbon nanofiber bundles were formed on silicon substrate using microwave plasma-enhanced chemical vapor deposition system. These bundles were vertically well-grown under the high negative bias voltage condition. The bundles were composed of the individual carbon nanofiber having less than 100 nm diameters. Turn-on voltage of the field emission was measured around 0.8 V/$\mu\textrm{m}$. Fowler-Nordheim plot of the measured values confirmed the field emission characteristic of the measured current.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.5
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• pp.203-209
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• 2006

For $P_B=50,\;{\Delta}T=10K$, Ar=5, Pr=2.36, Le=0.015, Pe=1.26, Cv=1.11, the intensity of solutal convection (solutal Grashof number $Grs=3.44x10^4$) is greater than that of thermal convection (thermal Grashof number $Grt=1.81x10^3$) by one order of magnitude, which is based on the solutally buoyancy-driven convection due to the disparity in the molecular weights of the component A($Hg_2Cl_2$) and B(He). With increasing the partial pressure of component B from 10 up to 200 Torr, the rate is decreased exponentially. The convective transport decreases with lower g level and is changed to the diffusive mode at 0.1 $g_0$. In other words, for regions in which the g level is 0.1 $g_0$ or less, the diffusion-driven convection results in a parabolic velocity profile and a recirculating cell is not likely to occur. Therefore a gravitational acceleration level of less than 0.1 $g_0$ can be adequate to ensure purely diffusive transport.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.2
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• pp.63-68
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• 2021

This study was focused to investigate the effect of NbC-coated crucible on the quality of the SiC crystals. Then, the different properties between SiC crystals grown in a conventional graphite crucible and NbC-coated crucible were systematically compared. SiC crystals were grown using the Physical Vapor Transport (PVT) method at a temperature of 2300℃ and a pressure of 5 Torr in Ar atmosphere. After grinding and polishing, the polytype of the grown SiC crystal was analyzed using Raman spectroscopy, and crystallinity was confirmed by HR-XRD. Furthermore, the defect density and the concentration of impurities were analyzed by an optical microscope and a SIMS, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.21.1-21.1
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• 2011

Vertically aligned single-crystal ZnO nanowires have been successfully grown on c-plane sapphire substrate using chemical vapor deposition (CVD) without catalyst. According to growth temperatures, it was changed ZnO growth characteristic. We investigated the effect of substrate temperatures on the growth ZnO films or nanowires on c-plane (0001) sapphire substrates. The ZnO films were acquired at $500^{\circ}C$, whereas the ZnO nanowires were obtained at $600^{\circ}C$, $700^{\circ}C$, and $800^{\circ}C$. The growth behavior diameter and growth rate of ZnO were changed due to different temperature. As a result of analyzing in-plane residual stress by X-ray diffraction, the optimized condition of ZnO nanowires were at $600^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.240-248
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• 1998

The plasma chemical vapor deposition is one of the most utilized techniques for the diamond growth. As the applications of diamond thin films prepared by plasma chemical vapor deposition(CVD) techniques become more demanding, improved fine-tuning and control of the process are required. The important parameters in diamond film deposition include the substrate temperature, $CH_4/H_2$ gas flow ratio, total, gas pressure, and gas excitation power. With the spectroscopic ellipsometry, the substrate temperature as well as the various parameters of the film can be determined without the physical contact and the destructiveness under the extreme environment associated with the diamond film deposition. It is introduced how the real-time spectroscopic ellipsometry is used and the data are analyzed with the view of getting the growth condition and the accompanied features for a good quality of diamond films. And it is determined the important parameters during the diamond film growth, which include the final sample will be measured with Raman spectroscopy to confirm the diamond component included in the film.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.1-5
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• 2015

For the special usage, the effort of developing AlN single crystals has been very hot in the world. The AlN-base UV LEDs are used on the field of sterilization, purification, curing and analyzing, which can advance human's living and medical processes etc.. AlN single crystals were grown by the PVT (Physical vapor transport) method. On the growing process, carbon crucibles with three different types such as normal size, taller than normal and wider than normal were used for comparison. The processing temperature was in the range of $1900{\sim}2100^{\circ}C$ and ambient pressure was 200~1 Torr. When the taller crucible was used, the sublimation mass was greater than normal dimension one but the best condition of growth changes widely. However the wider one gave much sublimation mass and growing condition was more stable than normal dimension. On limited growing furnace system, the changes of crucible dimension of PVT method provide the change of best condition for growth rate, as-grown crystal quality and growth condition stability.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.1
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• pp.1-6
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• 2022

In this research, a ring-shaped silicon carbide (SiC) single crystal manufactured using the PVT (Physical Vapor Transport) method was proposed to be applied to a SiC focus ring in semiconductor etching equipment. A cylindrical graphite structure was placed inside the graphite crucible to grow a ring-shaped SiC single crystal by the PVT method. SiC single crystal ring without crack was successfully obtained in case of using SiC single crystal wafer as a seed. A plasma etching process was performed to compare plasma resistance between the CVD-SiC focus ring and the PVT-SiC focus ring. The etch rate of ring materials in PVT-single crystal SiC focus ring was definitely lower than that of CVD-SiC focus ring, indicating better plasma resistance of PVT-SiC focus ring.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.304-307
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• 2002

A zinc oxide (ZnO) single crystal was used as a substrate in the hydride vapor-phase epitaxy (HVPE) growth of GaN and the structural and optical properties of GaN layer were characterized by x- ray diffraction, transmission electron microscopy, secondary ion mass spectrometry, and photoluminescence (PL) analysis. Despite a good lattice match and an identical structure, ZnO is not an appropriate substrate for application of HVPE growth of GaN. Thick film could not be grown. The substrate reacted with process gases and Ga, being unstable at high temperatures. The crystallinity of ZnO substrate deteriorated seriously with growth time, and a thin alloy layer formed at the growth interface due to the reaction between ZnO and GaN. The PL from a GaN layer demonstrated the impurity contamination during growth possibly due to the out-diffusion from the substrate.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.229-230
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• 1997