• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.3
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• pp.262-275
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• 1994

SiC/C functionally gradient materials (FGM) were deposited on the graphite substrate by the chemical vapor deposition method. The best deposition conditions of SiC/C FGM were $1300^{\circ}C, H_2/[SiCl_4+CH_4]=10, CH_4/[$SiCl_4+CH_4]=0.5-0.6$. Despite of discontinuous input gas ratio change, the FGM of which composition was continuously changed could be obtained and continuous structural change without definite interfaces was confirmed by the SEM observation.

• Journal of the Korean Ceramic Society
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• v.45 no.5
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• pp.280-284
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• 2008

In order to investigate residence time effect on the growth of ZrC film, the ZrC films grew with various system total pressure (P) and total flow rate (Q) by low pressure chemical vapor deposition because residence time is function of system total pressure and total flow rate. Thermodynamic calculations predict that the decomposition of source gases ($ZrCl_4$ and $CH_4$) would be low as increasing the residence time. Thermodynamic calculations results were proved by investigating deposition rate with various residence time. Deposition rate decreased with residence time of source gas increased. Besides, depletion effect accelerated diminution of deposition rate at high residence time. On the other hands, the deposition rated was increased as decreasing the residence time because fast moving of intermediate gas species decrease the depletion effect. The crystal structure was not changed with residence time. However, the largest size of faceted grain showed up to specific residence time and the size of grain was decreased whether residence time increase or not.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.580-584
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• 2007

The ZrC layer instead of SiC layer is a critical and essential layer in TRISO coated fuel particles since it is a protective layer against diffusion of fission products and provides mechanical strength for the fuel particle. In this study, we carried out computational simulation before actual experiment. With these simulation results, Zirconium carbide (ZrC) films were chemically vapor deposited on $ZrO_2$ substrate using zirconium tetrachloride $(ZrCl_4),\;CH_4$ as a source and $H_2$ dilution gas, respectively. The change of input gas ratio was correlated with growth rate and morphology of deposited ZrC films. The growth rate of ZrC films increased as the input gas ratio decreased. The microstructure of ZrC films was changed with input gas ratio; small granular type grain structure was exhibited at the low input gas ratio. Angular type structure of increased grain size was observed at the high input gas ratio.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.109-113
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• 2013

ZnO thin films were synthesized on Si substrates by MOCVD using diethyl zinc as a precursor. Effects of $O_2$/DEZ gas mixing ratio on the growth rate, surface morphology, preferred orientation, and electrical properties of the ZnO thin films were investigated with SEM, XRD, and Hall measurement. The surface reflectance variations of ZnO thin films were analyzed using laser-photometer apparatus. As the $O_2$/DEZ mixing ratio increased, growth rate and $I_{(002)}/I_{(101)}$ in XRD of ZnO thin films decreased, and the crystal structure was changed from columnar to planar structure. All ZnO films deposited at various CVD conditions exhibited c-axis (002) plane preferred orientation. The electrical properties of ZnO thin films mainly depended on the carrier mobility.

• ETRI Journal
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• v.28 no.6
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• pp.787-789
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• 2006

In this letter, we report that vertically well-aligned ZnO nanowires were grown on GaN epilayers and c-plane sapphire via a vapor-liquid-solid process by introducing a 3 nm Au thin film as a catalyst. In our experiments, epitaxially grown ZnO nanowires on Au-coated GaN were vertically well-aligned, while nanowires normally tilted from the surface when grown on Au-coated c-$Al_2O_3$ substrates. However, pre-growth annealing of the Au thin layer on c-$Al_2O_3$ resulted in the growth of well-aligned nanowires in a normal surface direction. High-resolution transmission electron microscopy measurements showed that the grown nanowires have a hexagonal c-axis orientation with a single-crystalline structure.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2431-2437
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• 2014

In this study, Ni, Ni-Cu and Ni/Cu catalysts were deposited onto C-fiber textiles via the electrophoretic deposition method, and the growth characteristics of carbon nanofibers on the deposited catalyst/C-fiber textiles were investigated. The catalyst deposition onto C-fiber textiles was accomplished by immersing the C-fiber textiles into Ni or Ni-Cu mixed solutions, producing the substrate by post-deposition of Ni onto C-fiber textiles with pre-deposited Cu, and passing it through a gas mixture of $N_2$, $H_2$ and $C_2H_4$ at $700^{\circ}C$ to synthesize carbon nanofibers. For analysis of the characteristics of the synthesized carbon nanofibers and the deposition pattern of catalysts, SEM, EDS, BET, XRD, Raman and XPS analysis were conducted. It was found that the amount of catalyst deposited and the ratio of Ni deposition in the Ni-Cu mixed solution increased with an increasing voltage for electrophoretic deposition. In the case of post-deposition of Ni catalyst onto substrates with pre-deposited Cu, both bimetallic catalyst and carbon nanofibers with a high level of crystallizability were produced. Carbon nanofibers yielded with the catalyst prepared in Ni and Ni-Cu mixed solutions showed a Y-shaped morphology.

• Transactions on Electrical and Electronic Materials
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• v.8 no.5
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• pp.206-210
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• 2007

Carbon nanotubes(CNTs) are largely synthesized on Fe catalysts by catalytic chemical vapor deposition. The various shapes and compositions of these nanostructure CNTs were obtained by controlled parameters such as the reaction temperature, gas-mixing ratio. The influence of these parameters is investigated, together with observations of the produced materials after the purification processes. A diameter of CNTs, range from 2 to 10 nm, closely correlated with the size of the catalyst particle found attached to the tube end. The yield of CNTs was estimated to be 88.5 % and the purities of CNTs thus obtained were more than 80 %. The experimental results were documented with field emission scanning electron microscopy and raman spectroscopy and transmission electron microscopy, both before and after the purification.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.286-286
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• 2010

The lack of homogeneously sized single-walled carbon nanotubes (SWNTs) hinders their many applications because properties of SWNTs, in particular electrical conduction, are highly dependent on the diameter and chirality. Therefore, the preferential growth of SWNTs with predetermined diameters is an ultimate objective for applications of SWNTs-based nanoelectronics. It has been previously emphasized that a catalyst size is the one crucial factor to determine the CNTs diameter in chemical vapor deposition (CVD) process, giving rise to several attempts to obtain size-controllable catalyst by diverse methods, such as solid supported catalyst, metal-containing molecular nanoclusters, and nanostructured catalytic layer. In this work, diameter-controlled CNTs were synthesized using a nanostructured catalytic layer consisting of Fe/Al2O3/Si substrate. The CNTs diameter was controlled by structural modification of Al2O3 supporting layer, because Al2O3 supporting layer can affect agglomeration phenomenon induced by heat-driven surface diffusion of Fe catalytic nanoparticles at growth temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.433-433
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• 2013

Graphene, $sp^2$-hybridized 2-Dimension carbon material, has drawn enormous attention due to its desirable performance of excellent properties. Graphene can be applied for many electronic devices such as field-effect transistors (FETs), touch screen, solar cells. Furthermore, indium tin oxide (ITO) is commercially used and sets the standard for transparent electrode. However, ITO has certain limitations, such as increasing cost due to indium scarcity, instability in acid and basic environments, high surface roughness and brittle. Due to those reasons, graphene will be a perfect substitute as a transparent electrode. We report the graphene synthesized by inductive coupled plasma enhanced chemical vapor deposition (ICP-PECVD) process on Cu substrate. The growth was carried out using low temperature at $400^{\circ}C$ rather than typical chemical vapor deposition (CVD) process at $1,000^{\circ}C$ The low-temperature process has advantage of low cost and also low melting point materials will be available to synthesize graphene as substrate, but the drawback is low quality. To improve the quality, the factor affect the quality of graphene was be investigated by changing the plasma power, the flow rate of precursors, the scenario of precursors. Then, graphene film's quality was investigated with Raman spectroscopy and sheet resistance and optical emission spectroscopy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.1-4
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• 2000

Thin films of hydrogenated amorphous silicon carbide compounds ($a-Si_{x}C_{1-x}:H$) of different compositions were deposited on Si substrate by RF plasma-enhanced chemical vapor deposition (PECVD). Experiments were carried out using silane (SiH$_4$) and methane ($CH_4$) as the gas precursors at 1 Torr and at a low substrate temperature ($250^{\circ}C$). The gas flow rate was changed with the other parameters (pressure, temperature, RF power) fixed. The substrate was Si(100) wafer and all of the films obtained were amorphous. The bonding structure of $a-Si_{x}C_{1-x}:H$films deposited was investigated by X-ray photoelectron spectroscopy (XPS) for the film compositions. In addition, the surface morphology of films was investigated by atomic force microscopy (AFM).