We present a theoretical study on local electronic properties of quantum-dot nanotubes formed by connecting pure semiconducting and metallic nanotubes via appropriate junctions. The junctions are formed by introducing pair-defects composed by heptagon and pentagon along the axial direction of pure nanotubes. We investigate the dependence of the confined electronic states with the characteristic sizes of the quantum dot taking it account different based-nanotube 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 function formalism and adopt real-space renormalization techniques in the derivation of local density of states.

Adopting a real-space tight-binding supercell approach, we investigate interface roughness effects in semiconductor heterostructures. AlAs/GaAs/AlAs (001) QWs of average width W are considered, in which one of the interfaces is planar and the other has a shape defined by periodic steps with amplitude A and wavelength lambda. The oscillator strength f of the fundamental transition in the well describes the optical nature of the heterostructures. By investigating the wavefunctions as a function of the interface parameter A, we conclude that the f behavior with A is an optical signature of the quantum well to quantum wire crossover in the heterostructures. Recently, photoluminescence experiments showed that hydrostatic pressure produces an increase in the optical eficiency of heterostructures in which the interfaces present a high degree of roughness. In order to investigate this optical behavior, we discuss hydrostatic pressure effects on rough-interface heterostructures.