Morphology-controllable growth of vertical ZnO nanorod arrays by a polymer soft template method: Growth mechanism and optical properties

Abstract

Vertically well-aligned ZnO nanorod arrays were synthesized on silicon substrate by a novel polymer soft template method. The ZnO nanorod arrays have been deposited by immersing a silicon substrate into an aqueous solution containing Zn(CH3COO)2·2H2O, Polyvinylpyrrolidone (PVP) and NH3·H2O at 99 °C and then being annealed in oxygen atmosphere. The effects of reaction conditions on the morphology, structure and optical properties of ZnO nanostructures were investigated. The morphology of ZnO nanostructures was demonstrated to be controllable by adjusting the pH values of PVP-Zn2+ complex solution, zinc acetate concentration and growth time, respectively. The nanorod arrays were hexagonal zincite ZnO and the c-axis orientation growth trend of ZnO became more and more obvious with increasing the pH values of PVP-Zn2+ complex solution from 7.5 to 10.5, the zinc acetate concentration from 5 mM to 200 mM, and the growth time from 1 h to 3 h, respectively. The concentration of deep level defects in ZnO was reducing with increasing the pH values of PVP-Zn2+ complex solution, zinc acetate concentration and growth time, respectively. A growth mechanism of vertical ZnO nanorod arrays based on PVP soft template is proposed.