ZnO nanostructures have been synthesized on sol-gel derived ZnO seeds using a modified hydrothermal method. X-ray diffraction and field-emission scanning electron microscopy studies showed that raw materials used for the hydrolysis of zinc salts affect the crystalline phase, morphology and crystallinity. Plate-like ZnO nanostructures were precipitated using potassium hydroxide. On the contrary, vertically aligned ZnO nanowire arrays were synthesized using hexamethylenetetramine. The most favorable combination of raw materials for the nanowire synthesis was found to be zinc nitrate and hexamethylenetetramine. The authors suggest that not only ZnO nanowire diameter but also the degree of c-axis orientation are strongly correlated with the hydrothermal temperature. The growth rate between the ZnO nanowire diameter and its length was considerably different. Based on the nucleation and crystal growth theory, it is concluded that the growth behavior of ZnO nanowires is governed by the adsorption of growth species onto the growth surface.

ZnO nanostructures, ZnO nanowire arrays, hydrothermal method, growth process.