Pentagons, heptagons and negative curvature in graphite microtubule growth

lijima, Sumio; Ichihashi, Toshinari; Ando, Yoshinori

doi:10.1038/356776a0

Cited by 882 publications

(441 citation statements)

References 9 publications

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“…The heptagonal carbon ring, on the other hand, makes the hexagonal network curve outward, forming a negative curvature (Figure 6c). 9 Both pentagonal and heptagonal carbon rings are required to accommodate the change of surface curvature, making it possible, theoretically, to form any geometrical surface. 10 The pentagon is the start of the spiral-shell growth model (Figure 6d).…”

Section: Growth Mechanismmentioning

confidence: 99%

Kinetically Controlled Growth of Helical and Zigzag Shapes of Carbon Nanotubes

2000

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This paper focuses on the growth mechanism of the multiwalled carbon nanotubes exhibiting helical and zigzag growth morphologies. Our data support a kinetically controlled growth model in which the creation rates of the pentagon and heptagon carbon rings determine the geometrical shapes of the nanotubes. The carbon nanotube is believed to be grown from a carbon cluster that is nucleated from a pentagon carbon ring followed by a spiral shell growth. The pairing of pentagonal-heptagonal (P-H) carbon rings is essential in forming the helical and zigzag structures. If there is no twist in the P-H orientation along the body of the carbon nanotube, a planar-spiral structure would be formed. If the P-H pairs twist their orientations along the growth direction of the nanotube, a helical structure would be formed. The periodicity and the coiling diameter of the helix are determined by the angle of the twist and the distance between the adjacent P-H pairs. If the P-H pairs are densely accumulated at a local region and the interpair distance is small, a node is formed, thus, the zigzag growth morphology.

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Section: Growth Mechanismmentioning

confidence: 99%

Kinetically Controlled Growth of Helical and Zigzag Shapes of Carbon Nanotubes

2000

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“…Although the presence of the SW defects is widely expected, experimental identification of this kind of defect has not been reported. Transmission electron microscope (TEM) is a useful tool to analyze structural defects such as pentagon and heptagon on nanotubes [17], because presence of this type defect causes bending of nanotube. However, the SW defect does not cause the bending, so it is not feasible to identify the SW defects by TEM.…”

Section: Identification Of the Stone-wale Defectmentioning

confidence: 99%

Defect and Carrier Dynamics in Nanotubes under Electronic Excitations: Time-Dependent Density Functional Approaches

Miyamoto¹

2004

Simulation of Semiconductor Processes and Devices 2004

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One of challenging application of carbon nanotubes is nano-scaled electronic device, in which precise control of defects and carriers is required in analogy of silicon-based technology. In this work, we show that optical excitations can be promising tools to analyze and control defects in nanotubes being alternative to conventional heattreatments. We performed ab initio calculations, which solve the time-dependent Schrödinger equations for electrons on real-time axis as well as classical Newton's equations of motions for ions. This method is also useful to investigate carrier dynamics under finite temperatures. These works were done under collaboration with

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“…CNTs have been proposed as leads and bridge molecules, since they possess a great versatility, allowing for metallic as well as semiconducting behavior, 3,4 depending on their diameter and chirality, that is, their degree of helicity. Nanotubes can be easily modified by introducing pentagons, heptagons or octagons into their hexagonal network, as was already shown 5,6 soon after their discovery. 7 By joining a metallic nanotube with a semiconducting one, a heterojunction is formed showing a transport behavior corresponding to that of a rectifying diode, as already seen experimentally; 8 actually several applications of CNTs in nanoscale devices have been already described.…”

Section: Introductionmentioning

confidence: 99%

Defective transport properties of three-terminal carbon nanotube junctions

Valle¹,

Tejedor²,

Cuniberti³

2005

Phys. Rev. B

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We investigate the transport properties of three terminal carbon based nanojunctions within the scattering matrix approach. The stability of such junctions is subordinated to the presence of nonhexagonal arrangements in the molecular network. Such "defective" arrangements do influence the resulting quantum transport observables, as a consequence of the possibility of acting as pinning centers of the correspondent wavefunction. By investigating a fairly wide class of junctions we have found regular mutual dependencies between such localized states at the carbon network and a strikingly behavior of the conductance. In particular, we have shown that Fano resonances emerge as a natural result of the interference between defective states and the extended continuum background. As a consequence, the currents through the junctions hitting these resonant states might experience variations on a relevant scale with current modulations of up to 75%.

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Pentagons, heptagons and negative curvature in graphite microtubule growth

Cited by 882 publications

References 9 publications

Kinetically Controlled Growth of Helical and Zigzag Shapes of Carbon Nanotubes

Kinetically Controlled Growth of Helical and Zigzag Shapes of Carbon Nanotubes

Defect and Carrier Dynamics in Nanotubes under Electronic Excitations: Time-Dependent Density Functional Approaches

Defective transport properties of three-terminal carbon nanotube junctions

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