Density-controlled hydrothermal growth of well-aligned ZnO nanorod arrays

Abstract

Density-controlled ZnO nanorod arrays (ZNAs) were prepared on pre-treatmentsubstrates by a hydrothermal approach under different conditions. The effectof substrate pre-treatment conditions on controlling the density of ZNAs wassystematically studied by scanning electron microscopy and x-ray diffraction. It isdemonstrated that the substrate pre-treatment conditions such as the concentration of theZnO colloid, spin coating times, and substrate annealing treatment have theirrespective influence on controlling the density of the ZNAs. The introduction of aZnO nanoparticle layer on the substrate not only helps to control the nanoroddensity but also has a strong impact on the orientation of the nanorod arrays.Although controlling the spin coating process has a similar mechanism to controllingthe concentration of colloid, it offers a convenient method to prepare a series ofZNAs with variable density. An annealing treatment of the substrate can influencethe microstructure of the ZnO seed layer and then influence the density of theZNAs.