Modulation Of The Transport Properties Of One-dimensional Carbon Based Nanostructures

One-dimensional carbon based nanostructures show attractive potential applications in future nanoelectronics due to their unique electronic properties. In this thesis, we study the effect of strain and hybrid structure on the transport properties of single-wall carbon nanotubes and graphene nanoribbons by using the first-principles non-equilibrium Green's function method.(1) We study the effect of gold-SWCNTs composite contacts on the transport properties of SWCNTs. The transport properties of SWCNTs are greatly improved by gold-SWCNTs composite contacts due to the strong coupling between carbon and gold atoms of the composite contacts. The current of SWCNT(5,5) with composite contacts is almost double that of the pristine one. As for SWCNT(10,0), the composite contacts depress the Schottky barrier between SWCNT(10,0) and gold electrodes, which results in a smaller threshold voltage. Moreover, the negative differential resistance characteristics occur in the devices of SWCNT(10,0) with composite contacts.(2) We study the transport properties of ZGNRs-ZBNNRs hybrid nanoribbons. The transport properties are highly improved with the transmission conductance around the Fermi level increasing to 3G0 instead of 1G0 in ZGNRs based hybrid systems and to 2G0 instead of the transmission gap in ZBNNRs based hybrid systems. The enhancement attributes to the coupling effect between B (N) atoms and C atoms at the interface of hybrid systems, which introduces one extra band at each side of the Fermi level. The transport enhancement around the Fermi level is insensitive to the substitution position in hybrid nanoribbons. Moreover, such enhancement remains in hybrid nanoribbons sandwiched into gold electrodes due to the additional transport channel introduced by the C-B interface.(3) We study the effect of deformation on the transport properties of GNRs. The transport properties of ZGNRs are insensitive to the arched deformation, while the transmission conductance of ZGNRs is notably depressed by the step-shaped deformation. As for the AGNRs, the open current is depressed by either arched or step-shaped deformation. However, its threshold voltage is only enlarged by the arched deformation. Moreover, the transmission conductance of ZGNRs around the Fermi level is insensitive to either transverse or longitudinal strain, which is similar to those of the pristine ones. It is because that the edge states of ZGNRs still offer excellent ballistic transport channels under strains.