ENHANCEMENT OF ORIENTATED GRAIN GROWTH AND PHOTO RESPONSE OF ZnO THIN FILM BY SILAR

ZnO thin films were prepared by Successive Ionic Layer Adsorption Reaction (SILAR) method. The variations in the oriented grain growth in the thin films annealed in oxygen, air, argon, nitrogen atmospheres and samples doped with aluminium annealed in air were studied. Oriented grain growth of the samples was measured by comparing the peak intensities of the XRD pattern. Oriented grain growth increases in the order of samples annealed in atmospheres of oxygen, air, argon, nitrogen and aluminium doped. From the SEM micrographs it is found that as the oriented grain growth increases the needle like structure disappears and flowered structure becomes prominent. When the oriented grain growth increases, crystallinity of the thin film improves, photo current and dark curret increases resistance and band gap decreases. ZnO thin films having good (002) orientation is a prerequisite for the fabrication of devices like UV diode lasers, acoustic optic devices etc. The results also indicate that the ZnO is beneficial to solar cells and photodynamic therapy technology. From energy dispersive X-ray analysis, it is inferred that oxygen vacancy creation is responsible for the enhanced oriented grain growth in ZnO thin films when samples are annealed in atmospheres of argon, nitrogen and aluminium doped.