Preparation of Pb(Zr 0.52 Ti 0.48 )O 3 thin films on Pt/RuO 2 double electrode by a new sol-gel route
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Preparation of Pb(Zr0.52 Ti0.48 )O3 thin films on PtyyRuO2 double electrode by a new sol-gel route Seung-Hyun Kim, Yong-Soo Choi, and Chang-Eun Kim Department of Ceramic Eng., YonSei University, 134 Shinchon-dong, Seoul, 120-749, Korea
Young-Jei Oh Division of Ceramics, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul, 130-650, Korea (Received 26 September 1996; accepted 12 November 1996)
Pb(Zr0.52 Ti0.48 )O3 (PZT) thin film on PtyRuO2 double electrode was successfully prepared by using a new alkoxide-alkanolamine, sol-gel method. It was observed that the use of PtyRuO2 double electrode reduced leakage current, resulting in a marked improvement in the leakage characteristics and more reliable capacitors. Typical P-E hysteresis behavior was observed even at low applied voltage of 5 V, manifesting greatly improved remanence and coercivity. Fatigue and breakdown characteristics, measured at 5 V, showed stable behavior, and no degradation in polarization was observed up to 1011 cycles.
I. INTRODUCTION
Lead zirconate titanate, Pb(Zr0.52 Ti0.48 )O3 (PZT), ferroelectric thin film capacitors have been investigated for nonvolatile memory applications.1–4 The most commonly used electrode has been Pt or PtyTi,5 because Pt or PtyTi has a small lattice mismatch and a low leakage characteristic for PZT capacitors. However, PZT thin film capacitors using Pt or PtyTi electrode have a severe polarization fatigue problem on repeated switching cycles. In order to solve such a problem, researchers have attempted to improve the fatigue characteristics of PZT thin film using a conductive oxide electrode such as RuO2 or La12x Srx CoO3 .6,7 PZT thin films on the conductive oxide electrodes have excellent resistance to polarization fatigue, but they revealed large leakage currents and are more susceptible to dielectric breakdown. In this paper, we propose PtyRuO2 double electrode and a new sol-gel method to make up for these drawbacks for PZT capacitors. Recently, among the various deposition methods of these thin film, the sol-gel process8–10 has been studied with great emphasis, because of its many advantages for preparing thin films, for example, simple process, homogeneous film thickness over large areas, and excellent control of stoichiometry. However, conventional sol-gel methods have revealed a serious aging problem with increasing storage time. To solve this problem, we used an alkoxide-alkanolamine system for PZT coating solution. The alkoxide-alkanolamine system10 had an excellent dissolving power for many inorganic salts and a long-term stability to hydrolysis and condensation reaction. In particular, Pb acetate trihydrate was easily dissolved in a solution of alkanolamine alcohol, while it was insoluble in the alcohol without the addition of alkanolamine. In addition, preparation of PZT sol and 1576
http://journals.cambridge.org
J. Mater. Res., Vol. 12, No. 6, Jun 1997
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film using this system was very simple and suitable for o
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