We investigate the electronic properties of metallic (7,7) carbon nanotubes (CNT) in the presence of a variety of tetra- and hexa-vacancy defects, by using the first principles density functional theory (DFT) combined with the non-equilibrium Green’s function technique. From the view point of energetic stability large vacancies tend to split into pentagon and heptagon (5-7) defects. However, this does not preclude the presence of “holes” in the carbon nanotube by the nanoelectronic lithography technique. We show that the states linked to large vacancies hybridize with the extended states of the nanotubes to modify their band structure. As a consequence, the hole-like defects in the CNT lead to more prominent electronic transport compared to the situation in the defective CNT consisting of pentagon-heptagon pair defects. Our study suggests the possibility to improve the electronic properties of a defective carbon nanotube via morphological modifications induced by irradiation techniques. 相似文献
In this paper, an implementation of energetic damping for fermionic transport simulations which respects particle conservation is presented. For this, nonhermitian terms in the Hamiltonian of the system are used. After an explanation of the method, it is demonstrated studying the current over time and I/V characteristics in the noninteracting resonant level model for spinless fermions.
Conductance through a system consisting of a wire with side-attached quantum dots is calculated. Such geometry of the device allows to study the coexistence of quantum interference, electron correlations and their influence on conductance. We underline the differences between ‘classical’ Fano resonance in which the resonant channel is of single-particle nature and ‘many-body’ Fano resonance with the resonant channel formed by Kondo effect. The influence of electron-electron interactions on the Fano resonance shape is also analyzed. 相似文献
A first-principles computational method based on the
hybrid density functional theory is developed to simulate the
electronic transport properties of oligomeric phenylene ethynylene
molecular junctions with H2O molecules accumulated in the
vicinity as recently reported by Na {\it et al.}
[\wx{Nanotechnology}{18} 424001 (2007)]. The numerical results show
that the hydrogen bonds between the oxygen atoms of the oligomeric
phenylene ethynylene molecule and H2O molecules result in the
localisation of the molecular orbitals and lead to the lower
transition peaks. The H2O molecular chains accumulated in the
vicinity of the molecular junction can not only change the
electronic structure of the molecular junctions, but also open
additional electronic transport pathways. The obvious influence of
H2O molecules on the electronic structure of the molecular
junction and its electronic transport properties is thus
demonstrated. 相似文献
We derive a formula for the quantum corrections to the electrical current for a metal out of equilibrium. In the limit of
linear current-voltage characteristics our formula reproduces the well known Altshuler-Aronov correction to the conductivity
of a disordered metal. The current formula is obtained by a direct diagrammatic approach, and is shown to agree with what
is obtained within the Keldysh formulation of the non-linear sigma model. As an application we calculate the current of a
mesoscopic wire. We find a current-voltage characteristics that scales with eV/kT, and calculate the different scaling curves for a wire in the hot-electron regime and in the regime of full non-equilibrium.
Received 13 June 2001 相似文献
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