Journal of Nanoscience and Nanoengineering Vol. 1, No. 4, 2015, pp. 259-264 http://www.aiscience.org/journal/jnn * Corresponding author E-mail address: shahanegs@yahoo.com (G. S. Shahane) Structural, Morphological and Optical Properties of Sol-Gel Spin Coated Al-doped Zinc Oxide Thin Films R. V. Vidap 1 , S. S. Bandgar 2 , G. S. Shahane 2, * 1 Department of Electronic Science, Modern College of Arts, Science & Commerce, Pune, MS, India 2 Department of Electronics, DBF Dayanand College of Arts & Science, Solapur, MS, India Abstract A sol-gel spin coating method has been successfully used to synthesize Al-doped ZnO thin films. The XRD studies show synthesis of phase pure ZnO thin films with hexagonal wurtzite structure. The lattice parameters are a=3.2568Å and c=5.2108Å. Al-doping enhances the preferential growth along (002) direction. The lattice parameters decrease with increase in Al-doping concentration. SEM studies show that with Al-doping the growth of the films takes place with porous structure embedded with nanogranules overgrown on the folded structure. This indicates that Al-doping has an influence on the surface morphology of the films. AFM studies show that the maximum surface roughness of the film increases with Al-doping concentration. Optical study revealed that band gap of ZnO is 3.25 eV with direct band to band transitions and decreases with Al-doping concentration. The properties of ZnO thin films can be effectively tailored with Al-doping. These synthesized Al- doped ZnO thin films can be effectively used in photocatalysis and gas sensor applications. Keywords Zinc Oxide Thin Films, Structural Characterization, Optical Properties Received: September 15, 2015 / Accepted: November 12, 2015 / Published online: January 8, 2016 @ 2015 The Authors. Published by American Institute of Science. This Open Access article is under the CC BY-NC license. http://creativecommons.org/licenses/by-nc/4.0/ 1. Introduction Transparent conducting oxide (TCO) films have been intensively investigated for their potential applications, such as flat-panel displays, liquid crystal displays, organic light- emitting diodes, thin-film transistors, and thin-film solar cells [1]. Among the various materials, zinc oxide is one of the technologically important transparent conducting materials. Compared to other II-VI group compounds, zinc oxide has a large band gap of 3.37 eV and rather large exciton binding energy, which makes the exciton state stable even at room temperature. The wide range of optical and electrical characteristics have made these films very adequate for several promising applications such as chemical sensors, piezoelectric transducers, transparent electrodes, light emitting diodes, laser diodes, ultra-violet photodetectors, varistors, SAW devices, gas sensors, etc [2-6]. The method and preparative conditions of ZnO nanoparticles are also very important to control the microstructure of the films and thus expected to influence the optical and electrical properties. Various techniques have been used to deposit pure and doped ZnO thin films on different substrates. These include spray pyrolysis [7], sol-gel [8, 9], RF sputtering [10, 11], SILAR [12], combustion [13] and chemical bath deposition [14]. Among these, the sol-gel technique has several advantages, such as deposition of high purity, homogeneous, cheaper, large-area films at relatively low temperatures [1]. The study of effect of dopants on optical properties of ZnO based nanostructures is very important for photonic applications. Compared to undoped semiconductors, doped materials offer the possibility of using the dopant to tune their optical and electronic properties. Therefore in addition