Studies on vertically grown and annealed ZnO nanorods synthesized through aqueous solution process

摘要

Zinc Oxide (ZnO) nanostructured thin films were grown by double dip method also known as successive ionic layer adsorption and reaction method on glass substrates using ammonium zincate solution. The structural and optical properties were studied after annealing the deposited films between 300 and 500 ℃. The films were characterized by X-ray diffraction, scanning electron microscopy and optical absorption measurement techniques. The hexagonal wurtzite structure of the synthesized samples as confirmed by the X-ray diffraction studies was found to be not affected by the annealing temperature. The crystallite sizes and lattice strain on the peak broadening of annealed ZnO thin films were studied. The scanning electron microscopy images of ZnO show vertically grown perfect hexagonal shaped nanorods with diameters ranging from 100 to 450 nm. A high transmittance along with low scattering or absorption losses is observed in the visible region for the films annealed between 300 and 500 ℃. This shows the good optical quality of the films and could be useful as transparent electrodes for application in industries. The ZnO films exhibit direct band gap transition with the band gap values lying between 3.12 and 3.35 eV. A red shift is observed in the absorption edge as the annealing temperature is increased. The variations in the crystal size and energy gap due to the annealing temperature of the ZnO deposited substrates make it a promising candidate for opto-electronic device application.