In-situ anisotropic growth of nickel oxide nanostructures through layer-by-layer metal oxidation

Abstract

This study reports the one-directional growth of single crystalline nickel oxide nanostructures that is facilitated by the oxidation of nickel nanoparticles. Layer-by-layer growth at the buried NiO/Ni interface was directly observed by in-situ high resolution transmission electron microscopy at 650°C in an oxygen partial pressure around 4 × 10 −4 Pa. Individual layers of NiO grow by ledge movement, i.e., disconnection migration along the oxide/metal interface plane. Oxidation at interfacial steps is governed by oxygen vacancy migration along the interface plane, while the junction between the oxide/metal interface and the gas phase serves as nucleation site. The results of this study demonstrate the applicability of the terrace-ledge-kink crystal growth model for reactive crystal growth processes at internal heterophase interfaces.