• Korean Journal of Materials Research
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• v.14 no.3
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• pp.175-180
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• 2004

SiC nanotubes were synthesized by CNT-confined reaction. Evaporated SiO gas reacted with carbon nanotubes by VS growth mechanism. By confineded reaction, carbon nanotube was changed to SiC nanotube, and synthesized SiC nanotube was filled partly by the gas reaction in the nanotubes. SiC nanotube's mean diameters were not changed than carbon nanotubes because of means ratio of $CO_2$ and SiO gas was maintained evenly during the process. This result was same of data of simulation. By TEM observastion, SiC nanotube was filled by reaction of inner wall of CNT and SiO gas through the VS reactions. Converted SiC nanotube's compositions were revealed Si and C of 1: 1 ratios at all sites of nanotube by EDS.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.83-89
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• 2004

SiC nanotubes were synthesized by SLS growth mechanism using various metal catalysts. Synthesized nanotubes had mean diameters of 20~50 nm and several $\mu\textrm{m}$ length. The kind of catalysts affected microstructures of SiC nanotubes by different diffusion routes. These differences are attributed to catalysts' physical properties and relative activities to the graphite substrate. Fe acted as a good catalyst of SLS growth mechanism. But in case of Ni, SiC nanotubes grew slowly. Optical property was measured by photoluminescence measurement. Relatively broad peak was obtained and mean peak positioned at about 430 nm. This result was the same as other nanocrystalline SiC materials, but was different from the results of bulk SiC probably due to quantum confinement effect and defect in the grown SiC nanotube.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.6
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• pp.454-459
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• 2003

We investigate the structure and properties of SiC (Silicon Carbide) nanotubes using molecular dynamics simulation based on the Tersoff bond-order potential. For small diameter tubes, the Si-C bond distance of SiC nanotubes decreases as the nanotube diameter is decreased, due to curvature of the nanotube surface. We find that Young's modulus of SiC nanotubes is somewhat smaller than that of the other nanotubes considered so far. However, Young's modulus for SiC nanotubes is larger than that of ${\beta}$-SiC and almost equal to the experimental value for SiC nanorod and SiC whisker. The strain energy of the SiC nanotubes is also lower than that of the other nanotubes. The lower strain energy of SiC nanotubes raises the possibility of synthesis of SiC nanotubes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.547-550
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• 2014

In this study, the electrical characteristics of the nickel (Ni)/carbon nanotube (CNT)/$SiO_2$ structures were investigated in order to analyze the mechanism of CNT in MOS device structures. We fabricated 4H-SiC MOS capacitors with or without CNTs. CNT was dispersed by isopropyl alcohol. The capacitance-voltage (C-V) and current-voltage (I-V) are characterized. Both devices were measured by Keithley 4200 SCS. The experimental flatband voltage ($V_{FB}$) shift was positive. Near-interface trap charge density ($N_{it}$) and negative oxide trap charge density ($N_{ox}$) value of CNT embedded MOS capacitors was less than that values of reference samples. Also, the leakage current of CNT embedded MOS capacitors is higher than reference samples. It has been found that its oxide quality is related to charge carriers and/or defect states in the interface of MOS capacitors.

• Advances in nano research
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• v.2 no.1
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• pp.23-56
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• 2014

The significant growth of the Si photovoltaic industry has been so far limited due to the high cost of the Si photovoltaic system. In this regard, the most expensive factors are the intrinsic cost of silicon material and the Si solar cell fabrication processes. Conventional Si solar cells have p-n junctions inside for an efficient extraction of light-generated charge carriers. However, the p-n junction is normally formed through very expensive processes requiring very high temperature (${\sim}1000^{\circ}C$). Therefore, several systems are currently under study to form heterojunctions at low temperatures. Among them, carbon nanotube (CNT)/Si hybrid solar cells are very promising, with power conversion efficiency up to 15%. In these cells, the p-type Si layer is replaced by a semitransparent CNT film deposited at room temperature on the n-doped Si wafer, thus giving rise to an overall reduction of the total Si thickness and to the fabrication of a device with cheaper methods at low temperatures. In particular, the CNT film coating the Si wafer acts as a conductive electrode for charge carrier collection and establishes a built-in voltage for separating photocarriers. Moreover, due to the CNT film optical semitransparency, most of the incoming light is absorbed in Si; thus the efficiency of the CNT/Si device is in principle comparable to that of a conventional Si one. In this paper an overview of several factors at the basis of this device operation and of the suggested improvements to its architecture is given. In addition, still open physical/technological issues are also addressed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.57-60
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• 2005

Semiconductor carbon nanotube was grown on oxided silicon wafer with atmosphere pressure chemical vapor deposition (APCVD) method and investigated the electrical property after thermal oxidation at $300^{\circ}C$ in air. The electrical property was measured at room temperature in air after thermal oxidation at $300^{\circ}C$ for various times in air. Semiconductor carbon nanotube was steadily changed to metallic carbon nanotube as increasing of thermal oxidation times at $300^{\circ}C$ in air. Some removed area of carbon nanotube surface was shown with transmission electron microscopy (TEM) after thermal oxidation for 6 hours at $300^{\circ}C$ in air.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.50-55
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• 2008

Carbon Nanotube (CNT) films were deposited with varying deposition temperature by RF plasma CVD on Fe catalysts deposited onto $SiO_2$ films grown thermally on the silicon wafer using $C_2H_2$ and $H_2$ gases. The Fe catalysts on silicon oxide film were made by RF magnetron sputtering. The grounded grid mesh cover on the substrate holder was used for depositing CNT thin films with high purity. The surface morphologies and chemical structure of deposited CNT films were characterized using SEM, Raman, XPS and TEM. It was observed that deposited CNTs films were carbon fiber type having Bamboo-like multiwall structure and CNT film grown at $600^{\circ}C$ was more dense than that at $550^{\circ}C$, but become less dense at $650^{\circ}C$.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.327-333
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• 2022

In this study, silicon/carbon nanotube/carbon (Si/CNT/C) composites for anode were prepared to improve the volume expansion of silicon used as a high-capacity anode material. Si/CNT were prepared by electrostatic attraction of the positively charged Si and negatively charged CNT and then hydrothermal synthesis was performed to obtain the spherical Si/CNT/C composites. Poly(vinylidene fluoride) (PVDF), polyacrylic acid (PAA), and styrene butadiene rubber (SBR) were used as binders for electrode preparation, and coin cell was assembled using 1.0 M LiPF₆ (EC:DMC:EMC = 1:1:1 vol%) electrolyte and fluoroethylene carbonate (FEC) additive. The physical properties of Si/CNT/C anode materials were analyzed using SEM, EDS, XRD and TGA, and the electrochemical performances of lithium-ion batteries were investigated by charge-discharge cycle, rate performance, dQ/dV and electrochemical impedance spectroscopy tests. Also, it was confirmed that both capacity and rate performance were significantly improved using the PAA/SBR binder and 10 wt% FEC-added electrolyte. It is found that Si/CNT/C have the reversible capacity of 914 mAh/g, the capacity retention ratio of 83% during 50 cycles and the rate performance of 70% in 2 C/0.1 C.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.66-66
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• 2011

Anodic titanium dioxide (TiO2) nanotubes are very attractive materials for gas sensors due to its large surface to volume ratios. The most widely known method for fabrication of TiO2 nanotubes is anodic oxidation of metallic Ti foil. Since the remaining Ti substrate is a metallic conductor, TiO2 nanotube arrays on Ti are not appropriate for gas sensor applications. Detachment of the TiO2 nanotube arrays from the Ti Substrate or the formation of electrodes onto the TiO2 nanotube arrays have been used to demonstrate gas sensors based on TiO2 nanotubes. But the sensitivity was much lower than those of TiO2 gas sensors based on conventional TiO2 nanoparticle films. In this study, Ti thin films were deposited onto a SiO2/Si substrate by electron beam evaporation. Samples were anodized in ethylene glycol solution and ammonium fluoride (NH4F) with 0.1wt%, 0.2wt%, 0.3wt% and potentials ranging from 30 to 60V respectively. After anodization, the samples were annealed at $600^{\circ}C$ in air for 1 hours, leading to porous TiO2 films with TiO2 nanotubes. With changing temperature and CO concentration, gas sensor performance of the TiO2 nanotube gas sensors were measured, demonstrating the potential advantages of the porous TiO2 films for gas sensor applications. The details on the fabrication and gas sensing performance of TiO2 nanotube sensors will be presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.213-213
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• 2000

Direct laser vaporization of transition-metal(Co, Ni)/graphite composite pellet produced single wall carbon naotubes(SWNT) in the condensing vapor in a heated flow cylinder-type tube furnace, Transition metal/graphite composite pellet target was made by mixing graphite, Co, and Ni in 98:1:1 atomic weight ratios, pressing the mixed powder, and curing it. The target was placed in a tube furnace maintained at 1200$^{\circ}C$ and Ar inert collision gas continuously flowed into the tube. The 2nd harmonic, 532nm wavelength light from Nd-YAG laser was used to vaporize the tube. The carbon nanotubes produced by the laser vaporization were accumulated on quartz tube wall. The raw carbon nanotube materials were purified with surfactants(Triton X-100) in a ultrasonicator. These carbon nanotubes were analyzed using SEM, XRD, and Raman spectroscopic method. The carbon nanotube growth on the Ni-patterned Si substrate was investigated by the CVD process. Transition-metal, Ni and CH4 gas were used as a catalyst and a reactant gas, respectively. The structure and the phonon frequencies of the carbon nanotubes formed on the patterned Si substrate were measured by SEM and Raman spectrometer.