title: Compared growth mechanisms of Zn-polar ZnO nanowires on O-polar ZnO and on sapphire.
abstract: Controlling the growth of zinc oxide nanowires is necessary to optimize the performance of nanowire-based devices such as photovoltaic solar cells, nano-generators, or light-emitting diodes. With this in mind, we investigate the nucleation and growth mechanisms of ZnO nanowires grown by metalorganic vapor phase epitaxy either on O-polar ZnO or on sapphire substrates. Whatever the substrate, ZnO nanowires are Zn-polar, as demonstrated by convergent beam electron diffraction. For growth on O-polar ZnO substrate, the nanowires are found to sit on O-polar pyramids. As growth proceeds, the inversion domain boundary moves up in order to remain at the top of the O-polar pyramids. For growth on sapphire substrates, the nanowires may also originate from the sapphire/ZnO interface. The presence of atomic steps and the non-polar character of sapphire could be the cause of the Zn-polar crystal nucleation on sapphire, whereas it is proposed that the segregation of aluminum impurities could account for the nucleation of inverted domains for growth on O-polar ZnO.
authors.affiliation: CEA, LETI, Minatec Campus, Grenoble, 38054, France. gperillat@gmail.com
authors.forename: G
authors.initials: G
authors.lastname: Perillat-Merceroz
authors.forename: R
authors.initials: R
authors.lastname: Thierry
authors.forename: P H
authors.initials: PH
authors.lastname: Jouneau
authors.forename: P
authors.initials: P
authors.lastname: Ferret
authors.forename: G
authors.initials: G
authors.lastname: Feuillet