Mechanisms of self-assembly in solution grown ZnO nanorods

The mechanisms for self-assembly of ZnO nanorods grown by chemical bath deposition are investigated in detail. Using a combination of scanning electron microscopy, x-ray diffraction and transmission electron microscopy, the growth mechanism of ZnO nanostructures from a solution was studied. The study revealed that the mechanism of nucleation is the crucial step in controlling the morphology, orientation and distribution of the nanostructures on a silicon substrate. In the absence of a seed layer, rods initially nucleated from eroded regions in precipitated Zn(OH)₂ lead to the formation of flower-like, hemi-spherically arranged nanorods. In the presence of a higher density seed layer, well-aligned nanorods form on the seed layer coated substrate as a result of competition between homogeneous and heterogeneous nucleation. In general, the initial precipitation of Zn(OH)₂ in a basic solution followed by its dissolution is suggested as the formation mechanism of ZnO. These findings may contribute to the understanding of the mechanism of self-assembly of ZnO nanorods and help to control and manipulate the ZnO architecture during solution growth.