Electronic states in zigzag carbon nanotube quantum dots

Local electronic properties of quantum dot nanotubes modeled by connecting pure semiconducting and metallic nanotubes via appropriate junctions are studied following a single π-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-well-like 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/semiconductor(metal)/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.