Morphological, Structural and Optical Properties of ZnO Thin Films Deposited by Dip Coating Method

Zinc oxide (ZnO) thin films were deposited on glass substrat by dip coating technique. The effects of sol aging time on the deposition of ZnO films was studied by using the field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and optical transmission techniques. The morphology of the films strongly depends on preparation route and deposition technique. It is noteworthy that films deposited from the freshly prepared solution feature indistinct characteristics; had relatively poor crystalline quality and low optical transmittance in the visible region. The increase in sol aging time resulted in a gradual improvement in crystallinity (in terms of peak sharpness and peak intensity) of the hexagonal phase for all diffraction peaks. Effect of sol aging on optical transparency is quite obvious through increased transmission with prolonged sol aging time. Interestingly, 72-168 h sol aging time was found to be optimal to achieve smooth surface morphology, good crystallinity and high optical transmittance which were attributed to an ideal stability of solution. These findings present a better-defined and more versatile procedure for production of clean ZnO sols of readily adjustable nanocrystalline size.