Comparison between quantum confinement effects of quantum wires and dots

Dimensionality is an important governing factor in the electronic structures of semiconductor nanocrystals. The quantum confinement energies in one-dimensional quantum wires and zero-dimensional quantum dots are quite different. Using large-scale first-principle calculations, we have systematically studied the electronic structures of semiconductor (including group IV, III-V, and II-VI materials) surface-passivated quantum wires and dots. We have found that the band-gap energies of quantum wires and dots have the same scaling with diameter for a given material. The ratios of band-gap increases between quantum wires and dots are material-dependent, and for most direct band-gap materials, this ratio is very close to 0.586, as predicted by simple effective-mass approximation. We also have found a highly linear polarization of photoluminescence in quantum wires. The degree of polarization decreases with the increasing temperature and quantum wire size.