Optimisation on the Growth and Alignment of ZnO Nanorods

Abstract

Synthesis of aligned ZnO nanorods (NRs) is important for electronic and optoelectronic devices. In this work we demonstrate the growth of ZnO nanorods by co-precipitation method using zinc nitrate and hexamine precursors. The samples were characterized by X-ray diffraction analysis, Scanning electron microscopy and Raman spectroscopy. On introducing the seeded substrate into the growth solution, the seeds offer nucleation sites for one-dimensional growth of ZnO nanorods. ZnO nanorod arrays grown on the successive ionic layer adsorption and reaction (SILAR) seed layer found to be irregular and non-uniform due to the etching of the seed substrate by growth solution. However, dip-coated seed substrate yielded uniform growth of ZnO nanostructures. ZnO nanostructures with flower-like morphology were obtained for pH of 9. On reducing the pH of the growth solution the flower morphology transformed into rod-like morphology with rod diameter of 200nm. On reducing the pH to 3 the diameter of the nanorods is decreased to 20 to 25nm. On reducing the precursor concentration the faceted morphology of the nanorods changed into needle-like shape (with sharp tips) along with reduction in diameter (about 20nm). The growth of uniform and vertically aligned ZnO nanorods is observed in dip-coated seed substrate with 5 pH. The results indicate that the diameter of ZnO nanorod array could be controlled by varying the precursor concentration.