• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.867-870
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• 2001

The carbon nanomaterials were prepared using the thermal chemical vapor deposition with ${C_2}{H_2}$ on the Ni-graphite mixture as a supported catalyst. The samples were identified by SEM, TEM, Raman spectroscopy, and the hydrogen storage measurement by electrochemical method was also carried out. The purity of carbon nanotube prepared using ground mixture was higher than that of unground one. Also, the amount of hydrogen storage of purified carbon nanomaterials was more than that of unpurified one.

• Bulletin of the Korean Chemical Society
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• v.28 no.4
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• pp.533-537
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• 2007

This paper describes the heteroepitaxial growth of single-crystalline 3C-SiC (cubic silicon carbide) thin films on Si (100) wafers by atmospheric pressure chemical vapor deposition (APCVD) at 1350 oC for micro/nanoelectromechanical system (M/NEMS) applications, in which hexamethyldisilane (HMDS, Si2(CH3)6) was used as a safe organosilane single-source precursor. The HMDS flow rate was 0.5 sccm and the H2 carrier gas flow rate was 2.5 slm. The HMDS flow rate was important in obtaing a mirror-like crystalline surface. The growth rate of the 3C-SiC film in this work was 4.3 μm/h. A 3C-SiC epitaxial film grown on the Si (100) substrate was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman scattering, respectively. These results show that the main chemical components of the grown film were single-crystalline 3C-SiC layers. The 3C-SiC film had a very good crystal quality without twins, defects or dislocations, and a very low residual stress.

• Journal of computational fluids engineering
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• v.18 no.3
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• pp.67-71
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• 2013

Recently, the rapid development of the semiconductor industry induces the prompt technical progress in the area of device integration and the application of large diameter wafers for the price competitiveness. As a result of the usage of large wafers in the semiconductor industry, the silicon carbide components which have layers of silicon carbide on graphite or RBSC substrates is getting widely used due to the advantages of SiC such as high hardness and strength, chemical and ionic resistant to all the environments superior than other ceramic materials. For the uniform and homogeneous deposition of silicon carbide on these huge components, it needs to know about the gas flow in the CVD reactor, not only for the delicate adjustment of the process variables but more essentially for the cost reduction for the shape change of specimens and their holders on the stage of reactor. In this research, the CFD simulation is challenged for the prediction of the inner distribution of the gas velocity. Chemical reaction simulation is used to predict the distribution of concentration of the reacting gas with the rotating velocity of the stage. With the increase of the rotating speed, more uniform distribution of the reacting gas on the surface of the stage was obtained.

• Journal of the Korean Ceramic Society
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• v.31 no.10
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• pp.1188-1196
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• 1994

TiN films were deposited onto high speed steel(SKH9) and silicon wafer by plasma-assisted chemical vapor deposition(PACVD) using a TiCl4/N2/H2/Ar gas mixture. The effects of deposition temperature, R.F. power, and H2 concentration on the deposition of TiN were studied. The residual chlorine content and the microhardness of TiN films were also investigated. It was found that TiN films grew with a columnar structure of a strong (200) preferred orientation regardless of the substrate type and the deposition variables. The TiN films consisted of columnar-grains of about 50 to 100 nm in diameter. The columnar grains themselves contained much finer fibrous grains. As deposition temperature increased, the residual chlorine content decreased sharply. R. F. powder enhanced the deposition rate largely. Increasing of H2 concentration had little effect on the residual chlorine.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.122-126
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• 2013

The surface roughness of the inner and outer surfaces of a tube is an important requirement for nuclear fuel cladding. When an inner SiC clad tube, which is considered as an advanced Pressurized Water Cooled Reactor (PWR) clad with a three-layered structure, is fabricated by Chemical Vapor Deposition (CVD), the surface roughness of the substrate, graphite, is an important process parameter. The surface character of the graphite substrate could directly affect the roughness of the inner surface of SiC deposits, which is in contact with a substrate. To evaluate the effects of the surface roughness changes of a substrate, SiC deposits were fabricated using different types of graphite substrates prepared by the following four polishing paths and heat-treatment for purification: (1) polishing with #220 abrasive paper (PP) without heat treatment (HT), (2) polishing with #220 PP with HT, (3) #2400 PP without HT, (4) polishing with #2400 PP with HT. The average surface roughnesses (Ra) of each deposited SiC layer are 4.273, 6.599, 3.069, and $6.401{\mu}m$, respectively. In the low pressure SiC CVD process with a graphite substrate, the removal of graphite particles on the graphite surface during the purification and the temperature increasing process for CVD seemed to affect the surface roughness of SiC deposits. For the lower surface roughness of the as-deposited interlayer of SiC on the graphite substrate, the fine controlled processing with the completed removal of rough scratches and cleaning at each polishing and heat treating step was important.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.380.2-380.2
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• 2014

Direct synthesis of graphene using a chemical vapor deposition (CVD) has been considered a facile way to produce large-area and uniform graphene film, which is an accessible method from an application standpoint. Hence, their fundamental understanding is highly required. Unfortunately, the CVD growth mechanism of graphene on Cu remains elusive and controversial. Here, we present the effect of graphene growth parameters on the number of graphene layers were systematically studied and growth mechanism on copper substrate was proposed. Parameters that could affect the thickness of graphene growth include the pressure in the system, gas flow rate, growth pressure, growth temperature, and cooling rate. We hypothesis that the partial pressure of both the carbon sources and hydrogen gas in the growth process, which is set by the total pressure and the mole fraction of the feedstock, could be the factor that controls the thickness of the graphene. The graphene on Cu was grown by the diffusion and precipitation mode not by the surface adsorption mode, because similar results were observed in graphene/Ni system. The carbon-diffused Cu layer was also observed after graphene growth under high CH4 pressure. Our findings may facilitate both the large-area synthesis of well-controlled graphene features and wide range of applications of graphene.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.146.2-146.2
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• 2013

Copper is considered to be the most promising substrate for the growth of high-quality and large area graphene by chemical vapor deposition (CVD), in particular, on the (111) facet. Because the interactions between graphene and Cu substrates influence the orientation, quality, and properties of the synthesized graphene, we studied the interactions using angle-resolved photoemission spectroscopy. The evolution of both the Shockley surface state of the Cu(111) and the ${\pi}$ band of the graphene was measured from the initial stage of CVD growth to the formation of a monolayer. Graphene growth was initiated along the Cu(111) lattice, where the Dirac band crossed the Fermi energy (EF) at the K point without hybridization with the d-band of Cu. Then two rotated domains were additionally grown as the area covered with graphene became wider. The Dirac energy was about -0.4 eV and the energy of the Shockley surface state of Cu(111) shifted toward the EF by ~0.15 eV upon graphene formation. These results indicate weak interactions between graphene and Cu, and the electron transfer is limited to that between the Shockley surface state of Cu(111) and the ${\pi}$ band of graphene. This weak interaction and slight lattice mismatch between graphene and Cu resulted in the growth of rotated graphene domains ($9.6^{\circ}$ and $8.4^{\circ}$), which showed no significant differences in the Dirac band with respect to different orientations. These rotated graphene domains resulted in grain boundaries which would hinder a large-sized single monolayer growth on Cu substrates.

• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.313-320
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• 2011

100 nm-thick hydrogenated amorphous silicon $({\alpha}-Si:H)$ films were deposited on a glass and glass/30 nm Ni substrates by inductively-coupled plasma chemical vapor deposition (ICP-CVD) at temperatures ranging from 100 to $550^{\circ}C$. The sheet resistance, microstructure, phase transformation and surface roughness of the films were characterized using a four-point probe, AFM (atomic force microscope), TEM (transmission electron microscope), AES (Auger electron spectroscopy), HR-XRD(high resolution X-ray diffraction), and micro-Raman spectroscopy. A nano-thick NiSi phase was formed at substrate temperatures >$400^{\circ}C$. AFM confirmed that the surface roughness did not change as the substrate temperature increased, but it increased abruptly to 6.6 nm above $400^{\circ}C$ on the glass/30 nm Ni substrates. HR-XRD and micro-Raman spectroscopy showed that all the Si samples were amorphous on the glass substrates, whereas crystalline silicon appeared at $550^{\circ}C$ on the glass/30 nm Ni substrates. These results show that crystalline NiSi and Si can be prepared simultaneously on Ni-inserted substrates.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.343-348
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• 1999

The iron silicide films were prepared by chemical vapor deposition method using rf-plasma in variations of substrate temperature. rf-power, and ratio of $SiH_4$ and Fe-precursor. While iron silicide films are generally grown by ion beam synthesis (IBS) method of multi-step process, it is confirmed that iron silicide or $\beta$-phase consolidated $Fe_aSi_bC_cH_d$ was formed by one-step process in this study. The characteristics of films is variable because the different amounts of carbon and hydrogen was involved in the films as a function of dilute ratio of Fe-precursors and silane. It was shown that the different characteristics of films in carbon and hydrogen following the ratio of Fe-precursor and silane. The optical gap energy of films fabricated according to substrate temperature was invariant because active site brought in desorption of hydrogen was limiled. When rf-power was above 240 watt, the optical gap energy turned out to have high values because of dangling bonds increased by etching.

• Journal of the Korean Applied Science and Technology
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• v.21 no.4
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• pp.289-299
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• 2004

Multi-walled carbon nanotubes (CNTs) were prepared by microwave plasma chemical vapor deposition (MPCVD) using various combination of binary catalysts and methane precursor. The maximum yield (10.3 %) of CNTs was obtained using a methane-hydrogen-nitrogen mixture with volume ratio of 1:1:2 at 1000 W of microwave power. As the microwave power increased up to 1000 W, the deposition yield of CNTs raised from 4.1 % to 10. 3 %. However, the prepared CNTs at 800 W showed the more crystalline structure than those prepared at 1000 W. The prepared CNTs over different binary catalysts had various structural conformations such as aligned cylinder, bamboo, and nanofibers. The Id/Ig value of CNTs over$Fe-Fe/Al_2O_3, $Co-Co/Al_2O_3, and $Co-Cu/Al_2O_3 were in the range of 0.89${\sim}$0.93. Among the various binary catalysts used, $Fe-Co./Al_2O_3 showed the highest yield.