Nanostructural growth investigation of Zno nanorods derived from chemical bath deposition for transparent heater application

One dimensional Zinc Oxide (ZnO) nanostructures in the forms of nanowire, nanorod, nanotube have been attracting scientific and technology interests in the last few years. This current study investigated the effects of chemical bath deposition (CBD) synthesis parameters i.e. seeding solution concentration and growing time on the nanostructural characteristics of ZnO nanorods and considering their potential application for transparent heater. Seed solutions were prepared by dissolving 1:1 equimolar zinc nitrate tetrahydrate and hexamethylenetetraamine in water at 0°C for 1 hour. Upon the synthesis, the seeding solution concentration was varied from 0.005, 0.025, 0.05 M. The formation of thin films containing ZnO nanoseeds was carried out by spin coating the precursors on the conducting indium tin oxide (ITO) glass substrates, followed with annealing at 200°C for 5 minutes then further growing the ZnO nanorods at 90°C for 3 hours. Another variation in this work was also carried out by selecting a different route upon CBD process, i.e. with a fixed 0.05 M seeding solution prepared from the same equimolar zinc nitrate tetrahydrate and hexamethylenetetraamine in water at 25°C for 1 hour, followed with the same annealing stage but continued by variation in the growing stage at 90°C for different times (3, 4 and 5 hours). ZnO nanorods were characterized using x-ray diffraction, field emission scanning electron microscopy and ultraviolet-visual spectroscopy. The results of these investigations demonstrated that with the increase in reaction time from 3 to 5 hours, the band gap energy, Eg of the nanorods decreased from 3.63 to 3.13 eV, a consequence of the increase in their diameter and crystallite size from 325 to 583 nm and 22.68 to 34.28 nm, respectively. The desired coverage of ZnO nanorods for transparent heater applications was obtained with a 0.05 M seeding solution and 5-hour reaction time.