Appraisal on Textured Grain Growth and Photoconductivity of ZnO Thin Film SILAR

ZnO thin films were prepared by successive ionic layer adsorption reaction (SILAR) method. The textured grain growth along c-axis in pure ZnO thin films and doped with Sn was studied. The structural analysis of the thin films was done by X-ray diffraction and surface morphology by scanning electron microscopy. Textured grain growth of the samples was measured by comparing the peak intensities. Textured grain growth and photo current in ZnO thin films were found to be enhanced by doping with Sn. ZnO thin film having good crystallinity with preferential (002) orientation is a semiconductor with photonic properties of potential benefit to biophotonics. From energy dispersive X-ray analysis, it is inferred that oxygen vacancy creation is responsible for the enhanced textured grain growth in ZnO thin films. 1. Introduction The synthesis and characterization of ZnO thin film have been an active area of research for nearly half a century. ZnO with wurtzite structure [1] is an n-type semiconductor with direct band gap of 3.37？eV [2, 3] and high electronic mobility. Due to wide and direct band gap semiconductor, nanostructure ZnO thin films have attracted more attention in optoelectronic devices [4]. The transparent conductive oxide (TCO) electrodes using Al-doped ZnO have been used as powerful candidate materials for ITO transparent electrodes. ZnO thin films have attracted much attention because they can be tailored to possess high electrical conductivity, high infrared reflectance, and high visible transmittance upon applying different techniques [5–8]. Different methods have been applied to obtain ZnO thin films. The important techniques include magnetron sputtering [6], chemical bath deposition [9], sol-gel [10], and spray pyrolysis [11]. Chemical deposition techniques are relatively low cost processes and can be easily scaled up for industrial application. Among the thin film deposition methods, double dip technique from aqueous solutions is the simplest and the most economical one. Double dip method otherwise called SILAR method (successive immersion layer adsorption reaction) [5, 12, 13] also offers the opportunity of doping the host ions with impurities on different kinds, shapes, and sizes on substrates with ease. Zinc oxide crystallites with preferential grain growth along -axis are desirable for applications such as UV diode lasers, piezoelectric surface acoustic wave or acoustic-optic devices, and gas sensors [4]. There are reports that textured grain growth along -axis in ZnO thin films is enhanced by doping and annealing. Controllable n-type