Nanostructured ZnO thin films prepared by sol-gel spin-coating

ZnO thin films deposited on silica flat plates were prepared by spin-coating and studied by applying several techniques for structural characterization. The films were prepared by depositing different numbers of layers, each deposition being followed by a thermal treatment at 200 degrees C to dry and consolidate the successive layers. After depositing all layers, a final thermal treatment at 450 degrees C during 3 h was also applied in order to eliminate organic components and to promote the crystallization of the thin films. The total thickness of the multilayered films - ranging from 40 nm up to 150 nm - was determined by AFM and FESEM. The analysis by GIXD showed that the thin films are composed of ZnO crystallites with an average diameter of 25nm circa. XR results demonstrated that the thin films also exhibit a large volume fraction of nanoporosity, typically 30-40 vol.% in thin films having thicknesses larger than similar to 70 nm. GISAXS measurements showed that the experimental scattering intensity is well described by a structural model composed of nanopores with shape of oblate spheroids, height/diameter aspect ratio within the 0.8-0.9 range and average diameter along the sample surface plane in the 5-7 nm range. (C) 2014 Elsevier B.V. All rights reserved.