<i>In situ</i>Observation of Carbon-Nanopillar Tubulization Caused by Liquidlike Iron Particles

Ichihashi, Toshinari; Fujita, Jun–ichi; Ishida, Masahiko; Ochiai, Yukinori

doi:10.1103/physrevlett.92.215702

Cited by 78 publications

(66 citation statements)

References 18 publications

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“…They accounted this to the surface tensional forces buildup at the core material/tube interface and the compressive stress during thickness growth of the graphitic wall. Similarly, Ichihashi et al [28] observed tubulization of carbon nanopillar and liquid-like behavior of iron particles in real time TEM measurements of a-C nanopillars. In our observations also catalyst particles are supposed to be in the liquid or quasi-liquid state during nanotube growth (as observed in Fig.…”

Section: Resultsmentioning

confidence: 99%

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Srivastava

Kumar

2010

Nano-Micro Lett

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The effect of hydrogen plasma treatment of iron oxide films on the growth and microstructure of carbon nanotubes (CNTs) by microwave plasma enhanced chemical vapor deposition process has been investigated. Microwave plasma was characterized in-situ using optical emission spectrometer. Morphology of the films was examined by scanning electron microscopy. Structural analysis was carried out by high resolution transmission electron microscopy (HRTEM) equipped with energy dispersive X-ray spectroscopy (EDS) and micro-diffraction attachments. It is found that oxide films without H 2 plasma pretreatment or treated for lesser time resulted in CNT films with high percentage of carbonaceous particles and with embedded particles/nanorods distributed discontinuously in the cavity of the nanotubes. The embedded particles were found to be of iron carbide (Fe-C) as confirmed by HRTEM, EDS and micro-diffraction analysis. Experimental observations suggested that the iron oxide particles had poor catalytic action for CNT growth and in-situ reduction of oxide clusters to Fe by hydrogen plasma plays a key role in discontinuous filling of the nanotubes by the catalytic particles. [12][13][14] have been used to synthesize CNTs. CVD methods (both thermal and plasma enhanced) are reliable in producing multiwalled CNTs (MWNTs) with proper control over the process parameters. Plasma enhanced CVD, however, can produce CNTs with a higher growth rate, at low temperature, and with better reproducibility. The plasma not only ionizes the gas but also causes a local surface heating [15]. Consequently, growth temperature could be significantly decreased compared to non-plasma CVD processes. In addition, the plasma atmosphere may also influence the detailed catalyst surface kinetics in many ways [16] and hence the growth of carbon nanostructures.Growth of CNTs and their microstructures depend on several parameters such as growth technique, feed gases, growth temperature, catalyst, and catalyst preparation method as well as their state (solid, liquid or vapor). In plasma assisted CVD processes, dilution gases play a critical role in the growth of CNTs and the structure of CNTs can be tailored by judicious control over gas composition [17]. In our earlier report, we investigated the effect of different dilution gases such as H 2 , NH 3 and N 2 and their different composition on the growth and microstructure of CNTs by microwave plasma enhanced CVD (MPECVD) process on Fe coated Si substrates using C 2 H 2 as feed gas [17]. Plasma pretreatment of catalyst film can also affect the growth and structure of CNTs significantly especially in a high frequency plasma process such as MPECVD. To the best of our knowledge, effect of H 2 plasma pretreatment of iron oxide films on the growth and structure of CNTs by MPECVD process have not been reported. Therefore, the motivation for the present

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Section: Resultsmentioning

confidence: 99%

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Srivastava

Kumar

2010

Nano-Micro Lett

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“…continual change in shape of the catalyst particle during SWNT growth. [2,15] Fig. 3 shows the Lindemann index for each atom in a Fe 300 C 60 cluster as a function of its average distance from the cluster center of mass at 1100, 1000, 900 and 800 K. It is evident that carbon and iron atoms in the center of the FeC cluster remain in their lattice positions at 800 and 900 K, whereas the surface atoms are mobile.…”

Section: Of 8 Saturday March 05 2005mentioning

confidence: 99%

Dependence of SWNT growth mechanism on temperature and catalyst particle size: Bulk versus surface diffusion

Ding

Rosén

Bolton

2005

Carbon

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The vapor-liquid-solid (VLS) model is often used to explain the growth of carbon nanotubes. [1] In this model the liquid catalyst particle acts i) as a catalyst for the decomposition of the carbon feedstock (e.g., CO, CH 4 or alcohols), ii) as a solvent for the carbon atoms that are released from the feedstock and iii) as a template for the nucleation and growth of the carbon nanotubes. However, recent experiments show direct evidence that carbon fibers can grow from solid 6-20 nm catalytic particles, [2] indicating that the particles do not need to be in the liquid phase for growth of onedimensional carbon structures. It was suggested that carbon atoms diffuse on the surface of these clusters, before they are incorporated in the fiber structure at step defects on the particle surface.Also, single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes (MWNTs) and carbon nanofibers (CNFs) can be produced at temperatures much lower the eutectic point of the bulk catalyst [3][4][5][6][7], and the melting point of the (rather large) catalyst particles used in the * Corresponding

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“…Transition metal catalyst is commonly utilized for graphitization [15], where the carbon atom was easily dissolved into the catalyst and excess carbon at the growth point produced sheet and/or tubular graphite [16]. But, the carbon was insoluble into gallium from the view point of macro-scale reaction, thus non of phase diagram was available.…”

Section: Introductionmentioning

confidence: 99%

Graphitization at interface between amorphous carbon and liquid gallium for fabricating large area graphene sheets

Fujita

Ueki

Miyazawa

et al. 2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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We have found that liquid gallium exhibits as a good graphitizing catalyst for a large area graphene sheet. While gallium and carbon are known to be an insoluble system, however, we have found that the catalytic reaction occurs at a very narrow interfacial region between amorphous carbon and liquid gallium. Amorphous carbon film was transformed into graphite layer composed of a few layers of graphene sheet. These thin graphene film can be easily transferred into silicon substrate through the intermediation of PDMS rubber stamping.

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In situObservation of Carbon-Nanopillar Tubulization Caused by Liquidlike Iron Particles

Cited by 78 publications

References 18 publications

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Dependence of SWNT growth mechanism on temperature and catalyst particle size: Bulk versus surface diffusion

Graphitization at interface between amorphous carbon and liquid gallium for fabricating large area graphene sheets

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