Properties of ZnO thin films deposited on (glass, ITO and ZnO:Al) substrates

ZnO thin films were deposited on glass, ITO (In2O3; Sn) and on ZnO:Al coated glass by spray pyrolysis. The substrates were heated at 350 degrees C. Structural characterization by X-ray diffraction (XRD) measurements shows that films crystallize in hexagonal structure with a preferential orientation along (0 0 2) direction. XRD peak-shift analysis revealed that films deposited on glass substrate (-0.173) were compressive, however, films deposited onto ITO (0.691) and on ZnO:Al (0.345) were tensile. Scanning electron microscopies (SEM) show that the morphologies of surface are porous in the form of nanopillars. The transmittance spectra indicated that the films of ZnO/ITO/glass and ZnO/ZnO:Al/glass exhibit a transmittance around 80% in the visible region. An empirical relationship modeled by theoretical numerical models has been presented for estimating refractive indices (n) relative to energy gap. All models indicate that the refractive index deceases with increasing energy band gap (E-g). (C) 2011 Elsevier Ltd. All rights reserved.