Novel approach to preparing well-oriented ZnO nanorods on substrates

Well-aligned single-crystalline wurtzite zinc oxide nanorods with high aspect ratio have been prepared by a low cost and low temperature hydrothermal approach. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and Raman spectroscopy have been used to characterize the ZnO nanorod arrays. SEM images indicate that ZnO hexagonal nanorods grow perpendicularly to the modified ITO substrates. The results of XRD and HRTEM reveal that ZnO nanorods grow along the [002] crystallographic face direction. Selected area electron diffraction (SAED) shows that ZnO nanorods are single-crystalline. Raman spectrum indicates that there is a very low concentration of oxygen vacancies in the highly oriented ZnO nanorod. SEM images show that more than 90% ZnO nanorods have diameter of 120 to 190 nm and the typical length is about 4 μm for the growth time of 2 h. In the meantime, the densely dispersed ZnO nanoparticles on substrates are found to be crucial for growing nanoscale ZnO rods oriented normal to the substrates.