Journal of Sol-Gel Science and Technology 13, 889–893 (1998) c  1998 Kluwer Academic Publishers. Manufactured in The Netherlands. Ferroelectric Thin Films of Bismuth Strontium Tantalate Prepared by Alkoxide Route E.P. TUREVSKAYA AND V.B. BERGO Moscow State University, Department of Chemistry, 119899 Moscow, Russia K.A. VOROTILOV AND A.S. SIGOV Moscow State Institute of Radioengineering, Electronics and Automation (Technical University), Vernadsky Prosp., 78, 117454 Moscow, Russia D. BENLIAN Universite de Provence, Lab. de Chimie de Coordination, Saint Jerome, 13397 Marseille, Cedex 20, France Abstract. Study of the interactions in Bi(OR) 3 -Ta(OR) 5 -ROH (R = Me, Et, i Pr) at 20 ◦ C show that metal ethoxides are the best of the investigated precursors for the production of bismuth tantalates via alkoxides. Polycrystalline SrBi 2 Ta 2 O 9 (SBTO) and BiTaO 4 films on Si-SiO 2 -Ti-Pt substrates with thicknesses of 0.4–0.5 μm and 0.4 μm, respectively, have been formed by sol-gel processing. The most stable solutions for film application were obtained by using mixed-metal Bi-Ta ethoxides and solutions of Sr carboxylate (2-ethylhexanoic acid derivative) in 2- ethylhexanoic acid. Films annealed at 700–750 ◦ C for 30 min were single-phased. SBTO films demonstrated good ferroelectric properties: remanent polarization ranged from 3.5 to 4.0 μC/cm 2 and coercive voltage 1.5–2.0 V, whereas BiTaO 4 films showed dielectric behavior. Keywords: sol-gel method, alkoxides, films, bismuth 1. Introduction Ferroelectric thin films have been intensively investi- gated during recent years as components of integrated circuits (ICs) [1, 2]. The two main applications of ferro- electrics are related to their physical properties: non- volatile random-access memory (NVRAM) based on polarization of ferrolectrics and its alteration by exter- nal electric field; and dynamic random-access memory (DRAM) in which the extremely high permittivity of ferroelectrics is utilized. The majority of recent studies have concentrated on lead zirconate titanate (PZT) films for NVRAM. PZT films have a high value of remanent polazrization and relatively low processing temperatures (550–650 ◦ C) for the production of the perovskite structure which is suitable for NVRAM technology (e.g., [3]). However, a major problem in the synthesis of PZT films is the volatility of PbO [4], which in many cases determines their crystalline structure and leads to oxygen vacancies and as a result to extensive fatigue in Pt/PZT/Pt capac- itor structures. The amount of switchable polarization commonly drops after ferroelectrics are subjected to repeated (about 10 8 cycles) polarization reversals as a result of domain pinning by space charge [5]. There are two major strategies to overcome the fa- tigue problem: the reduction of charge trapping at the interface by the use of oxide conductive electrodes (e.g., RuO 2 , LaSrCoO, etc.) and the control of defect density by vacancy compensation via donors doping or the use of ferroelectrics without volatile components thereby changing stoichiometry [3]. It has been demon- strated that PZT capacitors with oxide electrodes have practically no polarization fatigue up to about 10 12