• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.132-138
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• 2007

Carbon nanotubes (CNTs) arc grown on Ni catalysts employing an inductively-coupled plasma chemical vapor deposition (ICP-CVD) method. The structural and field-emissive properties of the CNTs grown are characterized in terms of the substrate-bias applied. Characterization using the various techniques, such as field-omission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Auger spectroscopy (AES), and Raman spectroscopy, shows that the structural properties of the CNTs, including their physical dimensions and crystal qualities, as well as the nature of vertical growth, are strongly dependent upon the application of substrate bias during CNT growth. It is for the first time observed that the provailing growth mechanism of CNTs, which is either due to tip-driven growth or based-on-catalyst growth, may be influenced by substrate biasing. It is also seen that negatively substrate-biasing would promote the vertical-alignment of the CNTs grown, compared to positively substrate-biasing. However, the CNTs grown under the positively-biased condition display a higher electron-emission capability than those grown under the negatively-biased condition or without any bias applied.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.6
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• pp.113-120
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• 2007

Chemical vapor deposition (CVD) is one of the various synthesis methods that have been employed for carbon nanotube (CNT) growth. In particular, Ren et al reported that large areas of vertically aligned multi-wall carbon nanotubes could be grown using a direct current (dc) PECVD system. The synthesis of CNT requires a metal catalyst layer, etchant gas, and a carbon source. In this work, the substrates consists of Si wafers with Ni-deposited film. Ammonia $NH_3$) and acetylene ($C_2H_2$) were used as the etchant gases and carbon source, respectively. Pretreated conditions had an influence on vertical growth and density of CNTs. And patterned growth of CNTs could be achieved by lithographical defining the Ni catalyst prior to growth. The length of single CNT was increased as niclel dot size increased, but the growth rate was reduced when nickel dot size was more than 200 nm due to the synthesis of several CNTs on single Ni dot. The morphology of the carbon nanotubes by TEM showed that vertical CNTs were multi-wall and tip-type growth mode structure in which a Ni cap was at the end of the CNT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.239-239
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• 2009

As we note the electric properties of carbon nanotube, we need to generate carbon nanotubes vertically. Generally, metal catalysts are used to synthesis carbon nanotubes. But through using DLC, dense patricles could be gotten easily. Compare to the case of using metal catalysts, the case of using DLC can conduct vertical grwoth of CNTs easily. In this paper, we changed growth temperature (550, 650, $7500^{\circ}C$) and growth time (3, 6, 9 min) in order to confirm synthesize vertical growth of CNTs on substrates.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.713-719
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• 2002

In this study, the vertically well-aligned CNTs were synthesized by DC bias-assisted inductively coupled plasma hot-filament chemical vapor deposition (ICPHFCVD) using radio-frequence plasma of high density and that CNTs were vertically grown on Ni(300 )/Cr(200 )-deposited glass substrates at 58$0^{\circ}C$. This system(ICPHFCVD) added to tungsten filament in order to get thermal decompound and DC bias in order to vertically grow to general Inductively Coupled Plasma CVD. The grown CNTs by ICPHFCVD were developed to higher graphitization and fewer field emission properties than those by general ICPCVD. In this system, DC bias was effect of vortical alignment to growing CNTs. The measured turn-on fields of field emission property by general ICPCVD and DC bias-assisted ICPHFCVD were 5 V/${\mu}{\textrm}{m}$ and 3 V/${\mu}{\textrm}{m}$, respectively.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.171-177
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• 2002

In this study, the vertical aligned carbon nanotubes was synthesized by DC bias-assisted Inductively Coupled Plasma Hot-Filament Chemical Vapor Deposition (ICPHFCVD). The substrate used CNTs growth was Ni(300 ${\AA}$)/Cr(200 ${\AA}$)-deposited one on glass by RF magnetron sputtering. R-F, DC bias and filament power during the growth process were 150 W, 80 W, 7∼8 A, respectively. The grown CNTs showed hollow structure and multi-wall CNTs. The top of grown CNT was found to Ni-tip that the CNT end showed to metaltip. The graphitization and field emission properties of grown was better than grown CNTs by ICPCVD. The turn-on voltage of CNT grown by DC bias-assisted ICPHFCVD showed about 3 V/${\mu}m$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.367-372
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• 2002

The vertically well-aligned carbon nanotubes(CNTs) were successfully grown on Ni coated silicon wafer substrate by DC bias-assisted PECVD(Plasma Enhanced Chemical Vapor Deposition). As a catalyst, Ni thin film of thickness ranging from 15~30nm was prepared by electron beam evaporator method. In order to find the optimum growth condition, the type of gas mixture such as $C_2H_2-NH_3$ was systematically investigated by adjusting the gas mixing ratio at $570^{\circ}C$ under 0.4Torr. The diameter of the grown CNTs was 40~200nm and the diameter of the CNTs increased with increasing the Ni particles size. TEM images clearly showed carbon nanotubes to be multiwalled. The measured turn-on field was $3.9V/\mu\textrm{m}$ and an emission current of $1.4{\times}10^4A/\textrm{cm}^2$ was $7V/\mu\textrm{m}$. The CNTs grown by bias-assisted PECVD was able to demonstrate high quality in terms of vertical alignment, crystallization of graphite and the processing technique at low temperature of $570^{\circ}C$ and this can be applied for the emitter tip of FEDs.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.38-39
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• 2006

We present experimental results that regard the effects of catalyst preparation on the structural and field-emissive properties of CNTs. The CNTs used in this research have been synthesized using the inductively coupled plasma-chemical vapor deposition (ICP-CVD) method. Catalyst materials (such as Ni, Co, and Invar 426) are varied and deposited on buffer films by RF magnetron sputtering. Prior to growth of CNTs, $NH_3$ plasma etching has also been performed with varying plasma etching time and power. For all the CNTs grown, nanostructures and morphologies are analyzed using Raman spectroscopy and FESEM, in terms of buffer films, catalyst materials, and pre-treatment conditions. Furthermore, the field electron-emission of CNTs are measured and characterized in terms of the catalyst preparation environments. The CNTs grown on Nicatalyst layer would be more effectual for enhancing the growth rate and achieving the vertical-alignment of CNTs rather than other buffer materials from results of SEM study. The crystalline graphitic structure of CNTs is improved as the catalyst dot reaches a critical size. Also, the field-emission result shows that the CNTs using Ni catalyst would be more favorable for improving electron-emission capabilities of CNTs compared with other samples.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.36-37
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• 2006

Both negative and positive substrate bias effects on the structural properties and field-emission characteristics are investigated. carbon nanotubes (CNTs) are grown on Ni catalysts employing an inductively-coupled plasma chemical vapor deposition (ICP-CVD) method. Characterization using various techniques, such as field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Auger spectroscopy (AES), and Raman spectroscopy, shows that the physical dimension as well as the crystal quality of CNTs grown can be changed and controlled by the application of substrate bias during CNT growth. It is for the first time observed that the prevailing growth mechanism of CNTs, which is either due to tip-driven growth or based-on-catalyst growth, may be influenced by substrate biasing. It is also seen that negative biasing would be more effectively role in the vertical-alignment of CNTs compared to positive biasing. However, the CNTs grown under the positively bias condition display much better electron emission capabilities than those grown under negative bias or without bias. The reasons for all the measured data regarding the structural properties of CNTs are discussed to confirm the correlation with the observed field-emissive properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.99-100
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• 2005

We have grown carbon nanotubes (CNTs) with a microwave plasma chemical vapor deposition (MPECVD) method, which has been regard as one of the most promising candidates for the synthesis of CNTs due to the vertical alignment, the low temperature and the large area growth. We use methane ($CH_4$) and hydrogen ($H_2$) gas for the growth of CNTs. 60 nm thick Ni catalytic layer were deposited on the TiN coated glass substrate by RF magnetron sputtering method. In this work, we report the effects of pressure on the growth of CNTs. We have changed pressure of processing (10 $\sim$ 20 Torr) deposition of CNTs. SEM (Scanning electron microscopy) images show diameter, length and cross section state CNTs.

• Journal of Information Display
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• v.2 no.3
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• pp.54-59
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• 2001

The role of $NH_3$ for vertical alignment of CNTs was investigated. The direct cause of the alignment was a dense distribution of catalytic metal particles, but which was kept catalytically active during the growth process by $NH_3$. This allows a dense nucleation of the CNTs, and consequently, assists vertical alignment through entanglement and mechanical leaning among the tubes. The CNTs grow in a base growth mode. Several evidences were presented including a direct cross-sectional TEM observation. Since Ni is consumed both by silicide reaction and by capture in the growing tube, the growth stops when Ni is completely depleted. This occurs faster for smaller particles, and thus a longer growth results in thin bottom with poor adhesion.