Properties of nanostructured ZnO thin films synthesized using a modified aqueous chemical growth method

Abstract

Research and development of nano-sized Zinc Oxide (ZnO) has recently received great attention due to its remarkable properties such as large exciton binding energy of 60 meV, extraordinary photosensitivity, nontoxic nature, wide bandgap and the fact that it is a low cost material with many technological applications. The inherent necessity for stoichiometric ZnO nanostructures suggest that a deposition method where the film stoichiometry is controlled by a chemical reaction is un-avoidable. Moreover, it is extremely important, when developing new methods for deposition of ZnO nanostructures to keep the deposition system as simple as possible, maximize throughput, and keep costs at a minimum. Modified aqueous chemical growth method offer such an opportunity. In this work, ZnO nano-petals on microscope glass substrates have been prepared by using a modified aqueous chemical growth method. On the other hand, before utilization of the fabricated ZnO nanostructures by any technique for any technological applications, it is essential to investigate morphological, optical, electrical and structural properties. In this work morphological, optical, electrical and structural properties with respect to change in deposition time have been cross examined using FESEM, UV–vis spectroscopy, I-V properties by Keithley system and XRD respectively. SEM micrographs have revealed very little changes in the shape, orientations and distribution of ZnO nano-petals formed with change in deposition times. SEM micrographs have also revealed the growth pattern for the prepared ZnO nano-petals which proceeds via a nucleation, and coalescence of ZnO nuclei. XRD analysis have revealed that the synthesized ZnO nano-petals have a hexagonal Wurtzite ZnO structure with peaks at 2θ positions 31.7°, 34.4°, 36.2°, 47.4°, 56.5° and 62.7° belonging to the (100), (002), (101), (102), (110) and (103) planes respectively. UV–vis spectroscopy has in the same way shown that the synthesized ZnO nano-petals have energy band gaps ranging from 3.46 eV to 3.65 eV. I-V measurements have disclosed that the ZnO nano-petals are conductive. Film resistivity values obtained from the I-V curves showed an exponential increase in resistivity with increased film thickness. Our method of preparation of ZnO nano-petals via a chemical assisted route can serve as benchmark for controlled synthesis of ZnO nanostructures for various technological applications.