Atomic force microscopy and spectroscopy studies of annealed Ce/Ti/Zr mixed oxide thin films prepared by sol–gel process F.E. Ghodsi a, * , F.Z. Tepehan b , G.G. Tepehan c a Department of Physics, Faculty of Science, The University of Guilan, Namjoo Ave. P.O. Box 41335-1914, Rasht, Iran b Department of Physics, Faculty of Sciences and Letters, Technical University of Istanbul, Mas/ak, Istanbul 34469, Turkey c Faculty of Arts and Sciences, Kadir Has University, Cibali, Istanbul 34083, Turkey Available online 22 May 2006 Abstract Mixed Ce/Ti/Zr oxide thin films with a molar ratio of 0.5:0.25:0.25 were prepared using the sol–gel process, and deposited on glass sub- strates by the dip coating technique. The effect of heat treatment temperature on surface morphology of the films was examined by atomic force microscopy, AFM. The optical transmittance and reflectance of the films were measured over the spectral range from 350 to 1000 nm. The refractive index and extinction coefficient and thickness of the films were determined as a function of the heat treatment temperature. The refractive index increased from 1.51 to 2.02 at k = 600 nm, and the extinction coefficient values increased from 0.006 to 0.094 while the thickness of the films decreased from 81 nm to 45 nm when annealing temperature increased from 100 °C to 500 °C. The results show that the optical properties and surface morphology of the mixed Ce/Ti/Zr oxide thin films were affected by annealing temperature. Ó 2006 Elsevier B.V. All rights reserved. Keywords: AFM; nkd Spectroscopy; Sol–gel; Thin films 1. Introduction Thin films of the metal oxide are very important due to their use in various applications such as optoelectronic [1,2], semiconductor gas sensing devices [3,4], photochromic [5] and electrochromic devices [6,7]. Metal oxide thin films can be prepared by the sol–gel process that offers a low-cost, rapid uniform coating of glass surfaces that renders it poten- tially interesting for various applications [8,9]. Sol–gel de- rived thin films that have not been annealed are too impure and too ill defined to be of use in the above-men- tioned devices [10]. In this work, we prepared mixed Ce/ Ti/Zr oxide thin films with molar ratio 0.5:0.25:0.25 by the sol–gel process using dip coating technique and annealed them at specific temperature between 100 °C and 500 °C. The effects of annealing temperature on the optical and structural properties of the samples studied by an nkd spec- trophotometer and atomic force microscope respectively. 2. Experimental 2.1. Thin film preparation Thin films of mixed Ce/Ti/Zr oxide were deposited using the sol–gel process by dip coating technique, from stabilized solutions prepared as described below. Ceric ammonium ni- trate was dissolved in ethanol as main precursor and stirred by magnetic stirrer for 30 min. Then, titanium butoxide, and zirconium propoxide were added into the mixture sep- arately. This mixture was stirred for 30 min. To accelerate hydrolysis and condensation, a small amount of acetic acid and distilled water were added to the mixture. The mixture was stirred for 24 h. A homogenous transparent solution was achieved. This mixed Ce/Ti/Zr oxide solution was aged for eight days at room temperature (16 ± 3 °C) with a humidity of (50% ± 5%) to achieve a highly transparent 0039-6028/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.susc.2006.02.078 * Corresponding author. Fax: +98 131 322 00 66. E-mail address: feghodsi@guilan.ac.ir (F.E. Ghodsi). www.elsevier.com/locate/susc Surface Science 600 (2006) 4361–4364