Materials Chemistry and Physics 114 (2009) 576–579 Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Dielectric properties of nanocrystalline Pb 0.8 Sr 0.2 TiO 3 thin films at different annealing temperature K.C. Verma a,∗ , R.K. Kotnala b , M.C. Mathpal b , N. Thakur a , Prikshit Gautam c , N.S. Negi a a Department of Physics, Himachal Pradesh University, Shimla 171005, India b National Physical Laboratory, New Delhi 110012, India c Department of Physics and Astrophysics, University of Delhi, Delhi 7, India article info Article history: Received 26 April 2008 Received in revised form 10 September 2008 Accepted 2 October 2008 Keywords: Thin films Chemical synthesis AFM Dielectric properties abstract Nanocrystalline Pb 0.8 Sr 0.2 TiO 3 (PST20) thin films have been synthesized by metallo-organic decompo- sition (MOD) technique and deposited on Pt/Ti/SiO 2 /Si substrates at different annealing temperatures of 550–750 ◦ C. The X-ray diffraction (XRD) confirms the distorted tetragonal perovskite phase in PST20 films. The average grain’s size varies from 35 nm to 46 nm as the annealing temperature increases from 650 ◦ C to 750 ◦ C as revealed by atomic force microscopy. At 550 ◦ C, the film shows low crystallization with incomplete perovskite structure. The study of dielectric properties of PST20 films is aimed at electrically tunable applications and to observe ferroelectric behaviors of PST20 films. The film annealed at 650 ◦ C shows large dielectric constant and higher tunability than the films annealed at 550 ◦ C and 750 ◦ C. The values of dielectric constant and tan ı at 1 MHz are 272 and 0.005, respectively, and tunability is ∼66% for PST20 film annealed at 650 ◦ C. The dispersionless dielectric properties are observed up to high frequency ∼8 MHz. The results suggest that the growth of uniform, dense and nano-sized grains in PST film makes it suitable for higher frequency device applications and electrically tunable devices. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Ferroelectric PbTiO 3 (PT) doping with Ca, Sr, Zr, etc. are being extensively investigated due to their excellent electrical, ferro- electric, piezoelectric and optical properties [1–3]. Lead calcium titanate (PCT) films have grain size in the range of 200–300 nm [4], which exhibit a high dielectric constant only at frequency <1 MHz. Recently, the synthesis of (Pb,Sr)TiO 3 (PST) thin films are in active research because their grains lie in nano-size. In our more recent work [5], we have observed that the nano-particles can produce dielectric and magnetic properties even up to higher frequency regions. It has been suggested that the small grains have high resis- tivity with a low leakage current. This type of improvements in PST films may be very useful for high frequency devices such as tunable mixers, phase shifter, voltage controlled oscillators, delay lines and for ultra large-scale integration dynamic random access memory (DRAM) capacitor [6–9]. The substitution of Sr for Pb in PT system can reduces grain size as well as phase transition tem- perature [10]. The reduction in grain size with increasing Sr content occurs because of lower grain-growth rates due to the slower diffu- ∗ Corresponding author. Tel.: +91 177 2830950; fax: +91 177 2830775. E-mail address: kuldeep0309@yahoo.co.in (K.C. Verma). sion of Sr 2+ ion with Pb 2+ [11]. In contrast to the other ferroelectric thin films, the substitution of Pb 2+ with Sr 2+ has been found to be more effective in reducing the dielectric loss or leakage current because of greater chemical stability of Sr 2+ ion. Therefore, PST thin films can be considered as a potential candidate material for future electrically tunable device components. Lead-based ferro- electric thin films are deposited by various methods such as sol–gel [12], rf-sputtering technique [13] and metallo-organic decomposi- tion (MOD) technique [4]. It is well known that the MOD process is a novel technique for preparing ferroelectric thin films because of its easy composition controllable, low cost, better homogeneity and non-vacuum process. In the present work, an attempt has been made to synthesize nanocrystalline Pb 0.8 Sr 0.2 TiO 3 (PST20) thin films by MOD tech- nique. The grain size in the films is investigated by X-ray diffraction (XRD) and atomic force microscopy. The frequency and tempera- ture dependent dielectric properties of PST20 films are studied as a function of annealing temperature. The tunability of the films is observed by measuring dielectric constant with different biasing voltage. 2. Experimental details Pb0.8Sr0.2TiO3 formulation was prepared by using Lead 2-ethylhexanoate (C7H15COO)2Pb, Strontium 2-ethylhaxanoate (C7H15COO)2Sr and tetra-n-butyl orthotitanate as precursors in xylene. The coating solution was prepared by mixing 0254-0584/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2008.10.012