• Bulletin of the Korean Chemical Society
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• v.24 no.12
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• pp.1771-1774
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• 2003

CNTs have been synthesized by catalytic $C_2H_2$ decomposition through $Pd/Al_2O_3$ at low temperature. The CNTs were grown to a length of about 10 ${\mu}$m and diameter 150-200 nm with multiwalled structure. Pd catalysts have two major roles; one is the active catalyst for $C_2H_2$ decomposition, the other is a nucleation site of CNT's growth.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1402-1404
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• 2009

The silicon nitride films for gate dielectric were deposited by catalytic chemical vapor deposition at low temperature (${\leq}200^{\circ}C$). The mixture of $SiH_4$, $NH_3$ and $H_2$ was used as source gases. The current-voltage (I-V) and the capacitance-voltage (C-V) characteristics of the films were measured. The breakdown voltage and the flat band voltage shift of samples were improved by increase of the $NH_3$ contents and $H_2$ dilution ratio. The defect states were analyzed by photoluminescence (PL) spectra. As the defect states decreased, the breakdown voltage and the flat band voltage shift increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.162-163
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• 2005

Singlewalled carbon nanotubes are largely synthesized on Fe-Mo/MgO catalysts by catalytic decomposition of CH4 in H2. Raman data revel that the as-prepared SWNTs have a diameter of about 0.7-1.2nm. It is found that the diameter of the as-prepared SWNTs can be controlled mainly by adjusting the molar ratio of Fe-MO versus the MgO support. The experimental results was documented with scanning electron microscopy(SEM), X-ray Diffractometer(XRD) and Raman spectroscopy.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.173-175
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• 2003

At the low temperature of $950^{\circ}C$ the $\mu\textrm{m}$-sized whisker growth during the catalytic CVD of pyrolytic carbon from methane with $H_2$- and Ar-gas on quartz substrate with NiO powder was found in this work. In the preliminary study it was observed from pure methane pyrolysis without catalyst at the high temperature $1500~1700^{\circ}C$. If the growth whisker should be stopped at initial stage, about 20 min. of the methane pyrolysis, it would be nanosized whisker growth. The screw growth mechanism and unique mechanical properties of whisker for composites were also recognized. If the pyrolysis would be continued, we could found also spiral growth of whistlers with diameter of about 1, 5 mm. The large length of whisker was about 10 cm in 20 minute.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.299-299
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• 2008

• Carbon letters
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• v.6 no.1
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• pp.31-40
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• 2005

The carbon nanofibers (CNFs) were synthesized through the catalytic decomposition of hydrocarbons in a quartz tube reactor. The CNFs prepared from $C_3H_8$ at $550^{\circ}C$ was selected as the purification sample due to the higher content of impurity than that prepared from other conditions. In this study, we carried out the purification of CNFs by oxidation in air or carbon dioxide after acid treatment, and investigated the influence of purification parameters such as kind of acid, concentration, oxidation time, and oxidation temperature on the structure of CNFs. The metal catalysts could be easily eliminated from the prepared CNFs by liquid phase purification with various acids and it was verified by ICP analysis, in which, for example, Ni content decreased from 2.51% to 0.18% with 8% nitric acid. However, the particulate carbon and heterogeneous fibers were not removed from the prepared CNFs by thermal oxidation in air and carbon dioxide. This result can be explained by that the direction of graphene sheet in CNFs is vertical to the fiber axis and the CNFs are oxidized at about the similar rate with the impurity carbon.

• 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.

• Carbon letters
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• v.5 no.2
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• pp.81-87
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• 2004

The effect of compositions of $Al_2O_3$ in the mixed $Fe/Al_2O_3$ catalysts on the synthetic behaviors of carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CCVD) process was investigated in wide range of the mixture ratios of support materials. CNTs were synthesized with $Fe/Al_2O_3$ catalysis under the condition of 40 min in synthetic time, and 923 K of synthetic temperature using $C_2H_4$ and $H_2$ as synthetic and carrier gas, respectively. The carbon yield with the content of $Al_2O_3$ showed in a parabolic curve and the maximum carbon yield was 40 wt.% of $Al_2O_3$. As the mixture ratio of $Al_2O_3$ increased, decreasing tendency was observed in the diameter of CNTs. Specific surface areas of CNTs were increased with the increase of the mixture ratio of $Al_2O_3$.

• Journal of the Korean Ceramic Society
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• v.52 no.3
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• pp.209-214
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• 2015

Silicon nitride films were deposited at $100^{\circ}C$ by using the catalytic chemical vapor deposition technique. The source gas mixing ratio, $R_N=[NH_3]/[SiH_4]$, was varied from 10 to 30, and the hydrogen dilution ratio, $R_H=[H_2]/[SiH_4]$, was varied from 20 to 100. The breakdown field strength reached a maximum value at $R_N=20$ and $R_H=20$, whereas the resistivity decreased in the same sample. The relative permittivity had a positive correlation with the breakdown field strength. The capacitance-voltage threshold curve showed an asymmetric hysteresis loop, which became more squared as $R_H$ increased. The width of the hysteresis window showed a negative correlation with the slope of the transition region, implying that the combined effect of $R_N$ and $R_H$ overides the interface defects while creating charge storage sites in the bulk region.