Structural, morphological and optical properties of Zinc Oxide Nanorods prepared by ZnO seed layer annealed at different oxidation temperature

Abstract

In this work, zinc oxide (ZnO) nanorods structure in the form of thin film have been grown on soda-lime glass (SLG) substrate incorporating two simple steps. Firstly, ZnO seed layer was pre-deposited onto the SLG substrate by the thermal evaporation method. During this process, the oxidation temperatures were varied in the range of 450 oC to 650 oC annealed for 3 hours. Then, the nanorods structure were grown on the surface of the seed layer by sol-gel immersion method with the use of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and hexamethylenetetramine (HMT) in deionized (DI) water. The optical, structural and morphological properties at different oxidation temperatures were studied using UV-Vis-NIR spectroscopy, X-ray diffraction (XRD) and Field-enhanced Scanning Electron Microscopy (FeSEM). The surface morphology results revealed the formation of hexagonal shaped ZnO on top of the seed layer as a result of heterogeneous nucleation. X-ray diffraction results show that the c-axis orientation became more prominent while the optical band gap of ZnO thin films decreases from 3.31 eV to 3.14 eV as the annealing temperature increased respectively. It is shown that the size and alignment of ZnO NRs are greatly affected by the pre-deposition annealed temperature of the ZnO seed layer on the surface of SLG substrate.