Influence of Al-doping on microstructure and optical properties of sol–gel derived CdO thin films Sinem Aydemir a,⇑ , Salih Köse a , M. Selami Kilickaya a , Vildan Özkan b a Department of Physics, Faculty of Science and Letters, Eskisehir Osmangazi University, Eskisehir 26480, Turkey b Department of Physics, Faculty of Science and Letters, Mus Alparslan University, Mus 49100, Turkey article info Article history: Received 6 February 2014 Received in revised form 4 March 2014 Accepted 6 March 2014 Available online 24 March 2014 Keywords: Sol–gel method Thin films Structural Roughness Optical properties Direct band gap abstract In this work, un-doped and Al doped cadmium oxide (CdO) films with different Al concentrations were grown onto ITO (In 2 O 3 ; Sn) glass substrates using sol–gel dip coating technique. The influence of Al doping on the structural, morphological and optical proper- ties of CdO thin films was systematically studied. XRD analysis showed that the films have poly-crystalline structures with cubic phase having (1 1 1), (2 0 0), (2 2 0) and (3 1 1) orientations. The AFM images were taken to see the effects of Al doping on surface topography and roughness of CdO thin films. From the SEM analy- sis, it has seen that nanostructured particles have homogeneously distributed and well hold onto the ITO substrate surface. The opti- cal properties were examined by a UV–vis spectrometer, which indicated high optical transparency in the visible region and a decrease of the direct band gap value from 3.03 to 2.77 eV, as the aluminum concentration in solution increases. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, there has been a lot of work on the production and investigation of the physical prop- erties of transparent conducting oxide (TCO) materials due to their interesting electrical and optical properties such as low resistivity and high optical transmittance [1–6]. The films of TCO such as zinc http://dx.doi.org/10.1016/j.spmi.2014.03.010 0749-6036/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +90 2222393750; fax: +90 2222393578. E-mail addresses: saydemir@ogu.edu.tr, sinemaydemir26@gmail.com (S. Aydemir). Superlattices and Microstructures 71 (2014) 72–81 Contents lists available at ScienceDirect Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices