The Significance of Plasma Heating in Carbon Nanotube and Nanofiber Growth

Teo, Kenneth B. K.; Hash, David; Lacerda, Rodrigo G.; Rupesinghe, N. L.; Bell, M. S.; Dalal, S. H.; Bose, Deepak; Govindan, T. R.; Cruden, Brett A.; Chhowalla, Manishkumar; Amaratunga, G.A.J.; Meyyappan, M.; Milne, W. I.

doi:10.1021/nl049629g

Cited by 136 publications

(85 citation statements)

References 36 publications

(68 reference statements)

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“…~700°C) whilst in this work, the power flux was ~5W/cm 2 (i.e. ~350°C [ [20]], similar to the highest temperatures we have measured during our growth). It is clear that low substrate temperatures and the growth of carbon nanotubes at relatively low substrate temperatures are possible.…”

Section: Resultssupporting

confidence: 79%

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Novel approach to low substrate temperature synthesis of carbon nanotubes

Chen

Poa

Stolojan

et al.

2006 IEEE Conference on Emerging Technologies - Nanoelectronics

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-We present a novel approach, which will potentially allow for low-temperature-substrate synthesis of carbon nanotubes using direct-current plasma-enhanced chemical vapour deposition. The approach utilizes top-down plasma heating rather than conventional heating from a conventional substrate heater under the electrode. In this work, a relatively thick titanium layer is used as a thermal barrier to create a temperature gradient between the Ni catalyst surface and the substrate. We describe the growth properties as a function of the bias voltage and the hydrocarbon concentrations. The heating during growth is provided solely by the plasma, which is dependent only on the process conditions, which dictate the power density and the cooling of the substrate, plus now the thermal properties of the "barrier layer". This novel approach of using plasma heating and thermal barrier allows for the synthesis of carbon nanotubes at low substrate temperature conditions to be attained with suitable cooling schemes.

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Section: Resultssupporting

confidence: 79%

“…~50°C [[20]]). The power flux used by Teo and co-workers [ [20]] was 20W/cm 2 (i.e. ~700°C) whilst in this work, the power flux was ~5W/cm 2 (i.e.…”

Section: Resultsmentioning

confidence: 73%

Novel approach to low substrate temperature synthesis of carbon nanotubes

Chen

Poa

Stolojan

et al.

2006 IEEE Conference on Emerging Technologies - Nanoelectronics

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“…Several modeling efforts have been presented in literature to describe the plasma chemistry in various types of plasma reactors used for carbon nanostructure growth, including dc plasmas [73][74][75][76], capacitively coupled rf plasmas [77,78], and inductively coupled plasmas (ICPs) [79][80][81][82][83][84][85]. These are either 0D chemical-kinetics models [79][80][81][82], 1D [73][74][75][76][77][78] or 2D [83][84][85] fluid approaches.…”

Section: (B) Cnts and Related Structuresmentioning

confidence: 99%

“…These are either 0D chemical-kinetics models [79][80][81][82], 1D [73][74][75][76][77][78] or 2D [83][84][85] fluid approaches. The gas mixtures considered in these models are the typical gases used for the growth of CNTs (and other carbon nanostructures), and consist of either CH 4 or C 2 H 2 as hydrocarbon growth precursors, mixed with H 2 or NH 3 as etchant gases, sometimes diluted with Ar.…”

Section: (B) Cnts and Related Structuresmentioning

confidence: 99%

Computer modelling of the plasma chemistry and plasma-based growth mechanisms for nanostructured materials

Bogaerts¹,

Eckert²,

Mao³

et al. 2011

J. Phys. D: Appl. Phys.

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In this review paper, an overview is given of different modeling efforts for plasmas used for the formation and growth of nanostructured materials. This includes both the plasma chemistry, providing information on the precursors for nanostructure formation, as well as the growth processes itself. We limit ourselves to carbon (and silicon) nanostructures. Examples of the plasma modeling comprise nanoparticle formation in silane and hydrocarbon plasmas, as well as the plasma chemistry giving rise to carbon nanostructure formation, such as (ultra)nanocrystalline diamond ((U)NCD) and carbon nanotubes (CNTs). The second part of the paper deals with the simulation of the (plasma-based) growth mechanisms of the same carbon nanostructures, i.e., (U)NCD and CNTs, both by mechanistic modeling and detailed atomistic simulations. IntroductionLow temperature plasmas are playing an increasingly important role for the formation and growth of nanostructures and nanostructured materials (e.g., [1][2][3][4][5][6][7]). To improve the performance of these plasma growth processes, a good insight is desired in the plasma and in the interaction with the growing nanostructures. This insight can be obtained by experimental research, but the latter is not always straightforward, in view of the small dimensions of the nanomaterials and the possible disturbance of the plasma characteristics, e.g., when introducing a probe. Therefore, computer simulations can be very useful to assist in the experimental developments.In the present paper, we will give an overview of different modeling efforts that have been presented in the literature for plasmas used for nanostructure formation. This includes two different aspects. First, a thorough understanding of the plasma behavior is needed. This comprises background gas flow and heating (i.e., fluid dynamics), gas breakdown, transport and heating of the electrons and the so-called heavy particles, as well as the plasma chemistry, i.e., creation and destruction of the various plasma species by chemical reactions. Modeling of the plasma chemistry can give indications on which species are important precursors for the growth of nanostructured materials and how the plasma operating conditions can be tuned to optimize the growth process. Therefore, in this paper we will mainly focus on the plasma chemistry modeling. Several plasma modeling approaches exist in literature, such as analytical models, zero-dimensional (0D) chemical kinetics simulations, fluid models (describing the chemical kinetics as well as fluid dynamics), solving the Boltzmann transport equation, Monte Carlo (MC) and particle-in-cell (PIC)-MC simulations, as well as hybrid methods, combining the above (e.g., MC + fluid) models. For describing the plasma chemistry, the 0D chemical kinetics approach is often applied, as it can take into account a large number of different species and reactions without too much computational effort. However, it assumes a spatially uniform plasma composition and does not consider transport of the plasm...

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“…This development has resulted in a variety of different techniques such as laser ablation, 1,2 arc discharge, 3,4 thermal chemical-vapor deposition (TCVD), [5][6][7] and plasma-enhanced chemical-vapor deposition (PECVD). [8][9][10] The laser ablation and the arc discharge techniques are efficient methods for producing large quantities of high-quality carbon nanotubes (CNTs) but they do not provide any control over the spatial arrangement of the resulting material 11 and therefore exhaustive post-growth processing is required to disentangle, redeposit, and align the nanotubes in order to fabricate a device. 12,13 On the other hand, catalytic TCVD and PECVD techniques allow for a more deterministic synthesis process.…”

mentioning

confidence: 99%

Vertically aligned carbon based varactors

Ghavanini

Enoksson

Bengtsson

et al. 2011

Journal of Applied Physics

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This paper gives an assessment of vertically aligned carbon based varactors and validates their potential for future applications. The varactors discussed here are nanoelectromechanical devices which are based on either vertically aligned carbon nanofibers or vertically aligned carbon nanotube arrays. A generic analytical model for parallel plate nanoelectromechanical varactors based on previous works is developed and is used to formulate a universal expression for their voltage-capacitance relation. Specific expressions for the nanofiber based and the nanotube based varactors are then derived separately from the generic model. This paper also provides a detailed review on the fabrication of carbon based varactors and pays special attention to the challenges in realizing such devices. Finally, the performance of the carbon based varactor is assessed in accordance with four criteria: the static capacitance, the tuning ratio, the quality factor, and the operating voltage. Although the reported performance is still far inferior to other varactor technologies, our prognosis which stems from the analytical model shows a promise of a high quality factor as well as a potential for high power handling for carbon based varactors.

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The Significance of Plasma Heating in Carbon Nanotube and Nanofiber Growth

Cited by 136 publications

References 36 publications

Novel approach to low substrate temperature synthesis of carbon nanotubes

Novel approach to low substrate temperature synthesis of carbon nanotubes

Computer modelling of the plasma chemistry and plasma-based growth mechanisms for nanostructured materials

Vertically aligned carbon based varactors

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