Electronic states in zigzag carbon nanotube quantum dots

Abstract

Local electronic properties of quantum dot nanotubes modeled by connecting pure semiconducting and metallic nanotubes via appropriate junctions are studied following a single -band tight-binding Hamiltonian. The junctions are formed by introducing pair defects composed of heptagons and pentagons along the axial direction of pure nanotubes. We investigate the dependence of the confined electronic states with the characteristic sizes of the quantum dots taking into account different nanotube-based heterostructures. Quantum-welllike and interface states are characterized by investigating the spatial dependence of the local density of states of the discrete levels. We follow the Green's function formalism and adopt real-space renormalization techniques to calculate local density of states. The conductance of metal/semiconductor͑metal͒/metal carbon heterostructures is also investigated and we found exponentially the decay and oscillatory behaviors that may be associated with the electronic structure of the tube constituents and the details of the junctions.

Ion and electron irradiation-induced effects in nanostructured materials

“…As demonstrated in numerous theoretical studies 11,[445][446][447][448][449][450][451] the presence of even a small number of defects can have a strong effect on electron transport in nanotubes, due to their quasi-1D structure. Experiments 11,21 also indicate that irradiation-induced defects strongly affect the resistivity of the samples, which normally increases by several orders of magnitude, depending on the original sample perfection and the conductivity regime.…”

Z-shaped graphene nanoribbon quantum dot device

“…Major experimental and theoretical breakthroughs have been achieved [2,3,4], combining two distinct chirality carbon-nanotubes by introducing topological point defects in the graphene hexagonal lattice, to realize the quantum dot in the carbon nanotube heterojunctions. In such devices, the major sources of spin decoherence have been identified as the spin orbit interaction, coupling the spin to lattice vibrations and the hyperfine interaction of the electron spin with the surrounding nuclear spins.…”

Electronic band structure of carbon nanotube superlattices from first-principles calculations

“…By introducing topological defects into the hexagonal carbon network, the nanotube chirality may change and therefore its electronic characteristics. In this way, two-terminal elements, such as metallic-semiconductor junctions, 7 quantum dots, [8][9][10][11] or superlattices, [12][13][14] can be designed. Carbon nanotube three-and four-terminal devices 15 and networks 16 have been also proposed in the same fashion, i.e., by joining nanotubes of different geometries via the introduction of topological defects.…”

“…Completely localized states have been predicted in semiconductor-metal-semiconductor ͑S / M / S͒ structures of diverse geometries. 8,9 All-metallic quantum dots have also been investigated; [9][10][11] in some of these systems, it is possible to achieve completely localized states by exploring the existence of a symmetry gap between metallic tubes of different symmetries. 11 Superlattices ͑SLs͒ made of carbon nanotubes have not been so widely studied.…”