No abstract

Thermal oxidation of Zn foils resulted in surface oxides with various morphologies depending on the oxidation temperature, time and atmosphere. Oxidation in air resulted in the formation of 3-dimensional ZnO nanosheets at 350 8C and at 400 8C ZnO nanorods were observed. ZnO nanorods were formed due to the fast diffusion mechanism of Zn 2+ at specific diffusion path whereas vapour-solid growth at temperatures near the sublimation temperature of the Zn induced the nanosheets formation. At lower temperatures than 350 8C and at shorter oxidation time, fine circular particulates formed on the Zn foil. This foil was then used as a seed layer for the growth of ordered nanostructures by either anodic oxidation or hydrothermal process. For the hydrothermal process, self-aligned single crystalline hexagonal nanorods were formed perpendicular to the seeded substrate by the reaction between hexamethyletramine (HMT) and Zn 2+ . On the other hand, anodic oxidation of the seeded Zn foil in KOH at 20V resulted in the formation of the uniform 3-dimensional nanosheets structure by dissolution and precipitation processes.