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Carbon-based Nanomaterials Doped First-principles Study Of The Effects And Chemical Modification

Posted on:2011-05-10Degree:MasterType:Thesis
Country:ChinaCandidate:J XiaoFull Text:PDF
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By performing first-principles electronic structure calculations, we have investigated the electronic structures of several sp2 Hybrid carbon-based nano-materials.Firstly, we have investigated the electronic properties of armchair single-walled carbon nanotubes (SWCNT) doped by boron/nitrogen (B/N) pair. It is found that for two kinds of sites in armchair SWCNT, B/N pair doping can more easily happen on the site which is at 30°angle to the tube axis. The energy gap of metallic SWCNT doped by B/N pair is opened, and the energy gap is increased with raising the axial concentrations of the B/N pair. Moreover, when two couples of B/N pair doping in SWCNT, the electronic structures are sensitive with the relative position of B/N pair along the circumference of tubes. The energy gap is increased with the increase of the distance of B/N pair.Secondly, we have the investigated electronic properties of graphene nano-ribbons (GNRs) doped by B/N pair, which two adjacent carbon atoms are replaced by B and N. It's found that B/N pair tends to be doped at the edge of GNRs, and B/N pair doping in GNRs is easier to be carried out than only B doping or B, N co-doping in which B and N are separated by carbon atoms. B/N pair doping can selectively adjust the energy gaps of armchair graphene nano-ribbons, and can remove the degeneracy of the eigenvalues near the Femi energy in zigzag graphene nano-ribbons.Finally, we have investigated electronic structure and chemical modification by hydroxyl groups of graphene antidot lattices (GALs). It's found that the electronic structures of GALs are sensitive to depend on the shape, size and hydroxyl groups'adsorption. The hexagonal-antidot GALs are typical semiconductor. However, some electronic localized states exist near the Fermi level in the triangular-antidot GALs and the number of electronic localized states is|nα-nβ|, which nα,βis the number ofα,βsublattices in a supercell. With the increase of the size of the antidot, the energy gap of the GALs would increase and the bandwidth of the localized states would decrease. Chemical activity of the atoms at the edge of the antidot could be enhanced by the adsorption of hydroxyl groups, comparing with perfect graphene. The adsorption of hydroxyl groups change the geometrical structures of the GALs, and make the hybrid type of adatom transform from sp2 to sp3, which would tune the electronic structures of the GALs.
Keywords/Search Tags:carbon-based nano-materials, doping effect, chemical modification, electronic structures, first-principles
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