Electronic bisection of a single-wall carbon nanotube by controlled chemisorption

Effect of extended line defects on thermal conduction of carbon nanotubes: analyzing phonon structures by band unfolding

We theoretically investigate the effect of extended line defects (ELDs) on thermal transport properties of carbon nanotubes (CNTs) using nonequilibrium Green's function method. Our study shows that the thermal conductance of CNTs with ELDs can be 25% lower than that of pristine CNTs. By extending the application of the recently developed unfolding method for electronic structures to phonon spectra, we find that the unfolded phonon bands of defected CNTs are split with obvious gap opening, leading to lower phonon transmissions. Further phonon local density of states analysis reveals that the change of bonding configuration near the ELD in defected CNTs can tail the degree of phonon localization. Our results indicate that introducing ELDs might be an efficient way to control thermal conduction of CNTs. The extended unfolding method for phonon systems, found to be efficient in this work, is expected to be applicable to other systems with densely folded phonon bands.

Half-metallic carbon nanotubes

Half-metallicity in carbon nanotubes is achieved and controlled by hydrogen adsorption patterns. The edge states in carbon nanotubes are unstable under an electric field due to the spin-conserving electron transfer between the edges, but a large enough transfer barrier between the edge states, obtained by controlling the adsorption patterns, renders the CNTs half-metallic.

Adsorptions of hydrogen on graphene and other forms of carbon structures: First principle calculations

Carbon can exist in various structural forms (graphite, graphene, graphene-nanoribbon and flake) and these are technologically very important materials. On the other hand, hydrogen incorporation in these materials can significantly affect their structural and electronic properties. As it is difficult to observe hydrogenation processes directly in experiment and to measure the electronic states at atomic scale, first-principle calculations are widely used to investigate the interaction between hydrogen and various carbon-based structures in past years. In this article, we briefly review work done in recent years, theoretical understanding on the interaction between hydrogen and different forms of carbon materials and present a number of strategies to modify the properties of carbon-based systems.

Mechanically robust tri-wing graphene nanoribbons with tunable electronic and magnetic properties

Inspired by strong mechanical stability of "Y"-shaped beams for building construction, we design a new class of quasi-one-dimensional graphene nanostructures, namely, tri-wing graphene (TWG) nanoribbons. TWG possesses significantly augmented mechanical stability against torsional and compression forces, and also each wing of the TWG can retain independent electronic properties of the constituent graphene nanoribbons. As such, by tailoring the wing structures, the TWGs can provide broader property tunability for nanoelectronic application. In addition, zigzag-edged TWG is a metallic ferromagnet with a large magnetic moment. When its edges are decorated with suitable chemical functional groups, a TWG can be converted to a half metal for potential spintronic applications.

Edge States and magnetism in carbon nanotubes with line defects

We apply first-principles calculations to investigate the interplay between electronic and magnetic properties of carbon nanotubes with line defects. We consider three types of defects: lines of C--O--C epoxy groups, and defects resulting from the substitution of the oxygen atoms by CH2 or C2H4 divalent radicals. We find that the line defects behave as pairs of coupled graphene edge states, and a variety of electronic and magnetic ground states is predicted as a function of defect type, nanotube diameter, and a possibly applied transverse electric field.