First-principles calculations of atomic and electronic properties of ZnO nanostructures

We employ density-functional theory within the generalized-gradient approximation to investigate the formation energies and atomic and electronic structure of ZnO nanowires and nanotubes (NTs). We find that relaxations on the facets of the bare wires are very similar to those in nonpolar $(10{\bar {1}}0)$ surfaces and play an important role in stabilizing the nanowires. All bare wires are found to be semiconducting, with band gaps larger than that in bulk ZnO. We further investigated hydrogen and water adsorption on ZnO nanowires. We find that the electronic structure of ZnO nanowires can be tuned by hydrogen adsorption and that adsorption of water leads to dissociation of a half-monolayer. Next, the stability of ZnO NTs has been investigated. We show that multiwall NTs are more stable than single-walled tubes. Finally, point defects in ZnO NTs have been investigated using spin-polarized calculations. All calculations were shown to introduce defect levels in the band gap, thus changing the electronic structure of the NTs drastically. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.