A study of microstructural and optical properties of nanocrystalline ceria thin films prepared by pulsed laser deposition G. Balakrishnan b,c , S. Tripura Sundari d , P. Kuppusami a, ⁎, P. Chandra Mohan e , M.P. Srinivasan e , E. Mohandas a , V. Ganesan f , D. Sastikumar b a Physical Metallurgy Division, Indira Gandhi Centre for Atomic Research,Kalpakkam-603 102, India b Department of Physics, National Institute of Technology, Tiruchirapalli-620015,India c Department of Physics, PERI Institute of Technology, Chennai-600048, India d Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research,Kalpakkam-603 102, India e Water and Steam Chemistry Division, BARCF, Kalpakkam-603 102, India f UGC-DAE Consortium for Scientific Research, Indore-452017, India abstract article info Article history: Received 3 May 2010 Received in revised form 30 November 2010 Accepted 3 December 2010 Available online 10 December 2010 Keywords: X-ray diffraction Thin films Cerium oxide Pulsed laser deposition Ellipsometry Thin films of cerium oxide (CeO 2 ) have been deposited on (100) Si substrates using pulsed laser deposition technique at various substrate temperatures from room temperature (RT) to 973 K at an optimized oxygen partial pressure of 3 Pa. Structural, morphological and optical properties have been carried out using X-ray diffraction (XRD), Raman, ellipsometry and atomic force microscopy techniques. XRD results showed that the deposited films are polycrystalline with cubic structure. At room temperature, the film showed preferred orientation along (111) plane, while at higher temperatures, it exhibited preferred orientation along (200). The crystallite sizes were calculated and were found to be in the range 17–52 nm. The texture coefficient for (200) reflection increased until 573 K, and then decreased in the temperature range 673–973 K. The Raman peak appeared at 463 cm -1 due to the F 2g active mode also confirmed the formation of CeO 2 with a cubic structure. There was a systematic variation in the Raman peak intensity, frequency shift and line broadening with the increase of temperature. The ellipsometry studies showed that the refractive index and band gap increased from 2.2 to 2.6 and 3.4 to 3.6 eV, respectively with increasing substrate temperature from RT to 973 K. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Cerium oxide (CeO 2 ) has generated a lot of interest because of its attractive properties and potential applications. It has physical properties such as high refractive index (2 at 500 nm), high melting point (2873 K), large dielectric constant (~ 26) [1], wide band gap (3.6 eV), high transparency in the visible-near infrared (VIS-NIR) regions, chemical stability, good adhesion, high hardness and thermal stability [2 – 4] . The lattice parameter of ceria (a = 0.541 nm) is very close to that of silicon (0.543 nm) and √2a of YBCO and it can be used as templates to grow epitaxial film, ultra thin gate oxide for complementary metal oxide semiconductor technology, stable capacitor devices for large scale integration, stable buffer layers between high temperature superconducting materials and silicon substrates [5]. Ceria thin film is also used in dynamic random access memory, colossal magneto resistance, ferroelectrics and corrosion protection coatings of metals and alloys [6–10]. Due to its wide band gap and good transparency in the VIS-NIR regions, it can also be used in ultraviolet (UV) blocking filters, single and multilayer coatings for optical devices [11] and electro-chromic windows [12]. It is an interesting material because of its high ionic conductivity when it is doped with divalent or trivalent cations, even at dopant concentrations as low as one mole percent. The defect in these materials is a consequence of the replacement of the host cations by aliovalent ions with compensation by oxygen vacancies. The conductivity is produced by the rapid transport of vacancies following conventional hopping mechanism. In the use of solid electrolytes, thin films have practical advantages for device fabrica- tion because of their improved reliability, size decrease, cost and electrical consumption. Ceria can store and release oxygen under oxidizing and reducing conditions, respectively. The ability to adsorb and release oxygen plays a critical role in the overall performance of the catalytic activity of ceria. This is due to the change in the oxidation state of Ce between Ce 3+ and Ce 4+ depending on the oxygen partial pressure in the surrounding atmosphere [13]. It is also a promising material for fast oxygen sensors at high temper- ature because of its chemical stability and high diffusion coefficient of oxygen vacancies. CeO 2 thin films have been prepared by several methods such as spray pyrolysis [3], ion beam–assisted deposition [4], thermal Thin Solid Films 519 (2011) 2520–2526 ⁎ Corresponding author. Tel.: + 91 44 27480306; fax: + 91 44 27480202. E-mail address: pk@igcar.gov.in (P. Kuppusami). 0040-6090/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2010.12.013 Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf