Materials Chemistry and Physics 65 (2000) 261–265 Fabrication and characterisation of (Ba,Sr)TiO 3 thin films by sol–gel technique through organic precursor route N.V. Giridharan, R. Varatharajan, R. Jayavel ∗ , P. Ramasamy Crystal Growth Centre, Anna University, Chennai-600 025, India Received 22 July 1999; received in revised form 4 January 2000; accepted 18 January 2000 Abstract Ferroelectric thin films of barium strontium titanate (BST) have been deposited on silicon and quartz substrates by sol–gel technique through organic precursor route. Crystalline films were obtained by post deposition annealing at a temperature of 700 ◦ C. X-ray diffraction (XRD) studies have been carried out to assess the crystallinity and phase formation. The surface features of the films, studied by optical microscopy reveal the grain growth pattern. The refractive index of the film has been estimated. Electrical characterisation of the films such as resistivity and C–V measurements in metal–ferroelectric–semiconductor (MFS) configuration have been carried out. The hysteresis behavior observed during the C–V measurements confirms the ferroelectric property of the films. © 2000 Elsevier Science S.A. All rights reserved. Keywords: BST thin films; Sol–gel technique; Optical and electrical characterisation 1. Introduction Ferroelectrics are a special group of advanced electronic materials consisting of dielectrics which are spontaneously polarized and possess the ability to switch their internal po- larization with an applied electric field. By far the largest number of applications of ferroelectrics are associated with bulk materials, but a trend towards ferroelectric thin films began during 1970s and has recently accelerated, partly be- cause of the techniques available for producing high qual- ity thin films and partly because of need and applications of such films [1]. Beside having advantages such as smaller size, lighter weight and easier integration, ferroelectric thin films have additional advantages such as lower operating voltage, higher speed and unique sub-micro level structure. Because of these properties ferroelectric thin films find ap- plications in the area of dielectric barrier layers [2], ultra- sonic transducers [3], modulators [4] and dynamic random access memories [5]. Barium titanate is a potential ferro- electric material whose Curie temperature is shifted below room temperature with the strontium doping, thus making (Ba,Sr)TiO 3 a room temperature paraelectric offering high dielectric constant, low leakage current and large dielectric breakdown strength [6]. Fabrication of BST thin films has been reported by different techniques such as r.f.magnetron ∗ Corresponding author. Tel.: +91-44-235-2774; fax: +91-44-235-2774. E-mail addresses: rjvel@annauniv.edu, rjvel@hotmail.com (R. Jayavel) sputtering [7], laser ablation [8], metal organic decompo- sition [9] and sol–gel process [10]. The sol–gel technique is gaining interest in the area of processing of thin films because of the advantages like, easier composition control, better homogeneity, low processing temperature, fabrication of large area thin films and low equipment cost. In this pa- per, fabrication of BST thin films through sol–gel route and their structural, optical and electrical characterisation have been reported. 2. Experiment 2.1. Solution preparation The precursor solution was prepared by acetic acid based sol–gel route [11]. Fig. 1 illustrates flow diagram for the preparation of precursor solution and films by sol–gel pro- cess. In this process the choice of precursor compounds and solvents plays a major role [12]. Barium acetate, strontium acetate and titanium (iv) butoxide were used as precursors. Glacial acetic acid and 2-methoxy ethanol were used as the solvents. Initially barium acetate and strontium acetate were taken in the ratio 70:30 and dissolved in acetic acid. Since barium acetate and strontium acetate partially dissolves in glacial acetic acid at room temperature, it was refluxed in a reflux condenser at a temperature of about 80 ◦ C for 4 h to obtain clear solution. After obtaining clear solution, 0254-0584/00/$ – see front matter © 2000 Elsevier Science S.A. All rights reserved. PII:S0254-0584(00)00231-5