Very High Yield Growth of Vertically Aligned Single-Walled Carbon Nanotubes by Point-Arc Microwave Plasma CVD

Zhong, Guofang; Iwasaki, Takayuki; Honda, Kôtarô; Furukawa, Yukio; Ohdomari, Iwao; Kawarada, Hiroshi

doi:10.1002/cvde.200404197

Cited by 93 publications

(102 citation statements)

References 25 publications

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“…16 The three-layered structure is suitable to obtain nanometer-sized catalyst particles. 17 In the experiment, the reactor was first pumped down to about 10 −6 Torr. Next, the Si substrate on the grounded electrode was heated to 500°C in 1 min in H 2 gas ͑H 2 99.99999% pure͒ at 4 -5 Torr.…”

Section: Methodsmentioning

confidence: 99%

Predicting the amount of carbon in carbon nanotubes grown by CH4 rf plasmas

Okita

Suda

Ozeki

et al. 2006

Journal of Applied Physics

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Carbon nanotubes ͑CNTs͒ were grown on Si substrates by rf CH 4 plasma-enhanced chemical vapor deposition in a pressure range of 1 -10 Torr, and then characterized by scanning electron microscopy. At 1 Torr, the CNTs continued growing up to 60 min, while their height at 4 Torr had leveled off at 20 min. CNTs hardly grew at 10 Torr and amorphous carbon was deposited instead. CH 4 plasma was simulated using a one-dimensional fluid model to evaluate the production and transport of radicals, ions, and nonradical neutrals. The amount of simulated carbon supplied to the electrode surface via the flux of radicals and ions such as CH 3 , C 2 H 5 , and C 2 H 5 + was consistent with estimations from experimental results.

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Section: Methodsmentioning

confidence: 99%

Predicting the amount of carbon in carbon nanotubes grown by CH4 rf plasmas

Okita

Suda

Ozeki

et al. 2006

Journal of Applied Physics

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“…Many of these properties, however, are highly anisotropic, thus it is desirable to control the orientation of SWNTs during synthesis. Significant advancements in this area have been made in the past few years, particularly regarding the synthesis of vertically aligned (VA-) SWNTs [7][8][9][10][11][12]. These synthesis methods, however, depend on several parameters such as temperature, pressure, flow rate, etc., and the underlying mechanism is not yet well understood.…”

Section: Introductionmentioning

confidence: 99%

Growth process of vertically aligned single-walled carbon nanotubes

Maruyama

Einarsson

Murakami

et al. 2005

Chemical Physics Letters

185

153

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We have performed a systematic investigation of the influence of growth parameters on the synthesis of vertically aligned single-walled carbon nanotubes (VA-SWNTs) by the alcohol catalytic chemical vapor deposition (ACCVD) method. The growth process of the VA-SWNTs was monitored using an in situ optical absorbance technique and the effects of CVD temperature and ethanol pressure on the initial growth rate and the catalyst lifetime were investigated. We found that for a given CVD temperature, there is an optimum pressure at which VA-SWNT film growth is maximized, and this pressure increases with temperature. Below this optimum pressure, the growth reaction is first-order, with the arrival of ethanol to the catalyst being the rate-limiting step. The activation energy of the growth reaction was determined to be approximately 1.5 eV.The root-growth mechanism of VA-SWNTs synthesized by the alcohol CVD method was also confirmed by a two-stage growth process. Following a short growth period using normal ethanol, 13 C -labeled ethanol was introduced to continue the growth. The location of the 13 C was determined from resonance Raman spectra, confirming the root-growth mechanism.

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“…The method presented here is also able to predict the critical lengths in different CVD processes from which carbon nanotube arrays begin to meet strong diffusion resistance, as well as the possible solutions to this diffusion caused growth deceleration. * To whom correspondence should be addressed.Fei Wei, weifei@flotu.org, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; tel, 86-10-62788984; fax, 86-10-62772051.Shigeo Maruyama, maruyama@photon.t.u-tokyo.ac.jp, Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Japan; tel, fax, Vertically aligned carbon nanotube (CNT) arrays grown on flat substrates [1][2][3][4][5][6][7] , in which all the nanotubes are of similar orientation and length, offer an ideal platform to study CNT growth mechanisms and kinetics. Since 1996 1 , various chemical vapor deposition (CVD) methods, including floating catalytic CVD 2 , plasma enhanced CVD 3 and thermal CVD 4 have been proposed to synthesize aligned multi-walled carbon nanotube (MWNT) arrays.…”

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confidence: 99%

Growth Deceleration of Vertically Aligned Carbon Nanotube Arrays: Catalyst Deactivation or Feedstock Diffusion Controlled?

et al. 2008

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Feedstock and byproduct diffusion in the root growth of aligned carbon nanotube arrays is discussed. A non-dimensional modulus is proposed to differentiate catalyst-poisoning controlled growth deceleration from one which is diffusion controlled. It is found that, at current stage, aligned multi-walled carbon nanotube arrays are usually free of feedstock diffusion resistance while single-walled carbon nanotube arrays are already suffering from a strong diffusion resistance. The method presented here is also able to predict the critical lengths in different CVD processes from which carbon nanotube arrays begin to meet strong diffusion resistance, as well as the possible solutions to this diffusion caused growth deceleration. * To whom correspondence should be addressed.Fei Wei, weifei@flotu.org, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China; tel, 86-10-62788984; fax, 86-10-62772051.Shigeo Maruyama, maruyama@photon.t.u-tokyo.ac.jp, Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Japan; tel, fax, Vertically aligned carbon nanotube (CNT) arrays grown on flat substrates [1][2][3][4][5][6][7] , in which all the nanotubes are of similar orientation and length, offer an ideal platform to study CNT growth mechanisms and kinetics. Since 1996 1 , various chemical vapor deposition (CVD) methods, including floating catalytic CVD 2 , plasma enhanced CVD 3 and thermal CVD 4 have been proposed to synthesize aligned multi-walled carbon nanotube (MWNT) arrays. Lately, alcohol catalytic CVD 5 (ACCVD), water assisted CVD 6 , microwave plasma CVD 7 , etc. are used to produce vertically aligned single-walled carbon nanotube (SWNT) arrays. These processes usually involve different catalysts, carbon sources and operation parameters, resulting in products with different morphologies and qualities. However, none of these CNT growth processes can overcome the gradual deceleration and eventual termination of growth. The ability to understand and thereby to overcome the underlying deactivation mechanisms becomes one of the most critical steps to develop nano-scale tubes into real macroscopic materials. Recently, many groups have affirmed the root growth mode of their vertically aligned CNTs, indicating that the feedstock molecules have to diffuse through the thick CNT array, reach the substrate where catalysts are located, and then contribute to the CNT growth. [8][9][10][11][12][13] In this bottom-up growth process, the diffusion resistance of the feedstock from the top to the root arises as an obstruction, and can act as a unique decelerating growth mechanism. Existence of a feedstock diffusion resistance means that concentration of the carbon source at the CNT root should be lower than the bulk concentration. Previously, Zhu et al.14 fitted experimentally-obtained film thicknesses with the square root of growth time, and stated that the growth deceleration is attributed to the strong diffusion limit of feedstock to the CNT root. However, Hart et al. 15 claimed later tha...

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Very High Yield Growth of Vertically Aligned Single-Walled Carbon Nanotubes by Point-Arc Microwave Plasma CVD

Cited by 93 publications

References 25 publications

Predicting the amount of carbon in carbon nanotubes grown by CH4 rf plasmas

Predicting the amount of carbon in carbon nanotubes grown by CH4 rf plasmas

Growth process of vertically aligned single-walled carbon nanotubes

Growth Deceleration of Vertically Aligned Carbon Nanotube Arrays: Catalyst Deactivation or Feedstock Diffusion Controlled?

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