Ferroelectric property of an epitaxial lead zirconate titanate thin film deposited by a hydrothermal method
- PDF / 4,365,843 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 75 Downloads / 250 Views
C11.31.1
Ferroelectric property of an epitaxial lead zirconate titanate thin film deposited by a hydrothermal method Takeshi MORITA, Yasuo WAGATSUMA, Yasuo CHO Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi, 980-8577, Japan Hitoshi MORIOKA, Hiroshi FUNAKUBO Department of Innovative and Engineered Materials, Tokyo Institute of Technology, GI-405, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502, Japan Setter NAVA Ceramics Laboratory, Faculty of Engineering, Material Institute, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland ABSTRACT Hydrothermal method has various advantages; low deposition temperature, high-purity, deposition on a three-dimensional structure and a large thickness. Although epitaxial PZT thin film deposition has reported, ferroelectric measurement has not been conducted due to the peel-off morphology of the film. The present paper investigates the improvement of an epitaxial PZT thin film deposited via a hydrothermal method. By adjusting the position at which the substrate was suspended in the solution, smooth morphology surface was successfully obtained. As a bottom electrode, 200 nm SrRuO3 thin film was deposited on SrTiO3 single crystals, and the PZT thin was deposited on SrRuO3 . The remanent polarization 2Pr for PZT on SrRuO3 /SrTiO3 (001) was 19.5 µC/cm2 and that of PZT on SrRuO3 /SrTiO3 (111) was 37.2 µC/cm2 , respectively. The self alignment poling direction was confirmed via scanning nonlinear dielectric microscopy and is thought to have been related to the deposition mechanisms. INTRODUCTION Epitaxial ferroelectric thin films, particularly lead zirconate titanate (PZT) epitaxial thin films, have been intensively studied for use in smart micro electrical mechanical systems (MEMS) and a Ferroelectric random access memory (FeRAM) due to their large piezoelectric displacement and permanent polarization1,2 . The advantage of the hydrothermal method is low reaction temperature, less than 200o C. It is important to note that this temperature is below the Curie temperature of PZT and more than 400o C below the reaction temperature required of other methods. Generally, a high temperature procedure results in lead evaporation. This lead vacancy causes the generation of a sub-phase, such as a pyrochlore phase. Excess strain remains in the structure due the phase change that occurs at the Curie temperature and the difference in the thermal expansion coefficient between PZT and the substrate. A chemical reaction is carried out on the substrate in some of the alternative deposition methods; hence relict by-products might be observed in the ferroelectric films. On the other hand, using the hydrothermal method, the PZT thin film is synthesized directly as an ionic reaction in solution, making it possible to obtain a high-quality ferroelectric thin film. The three dimensional structure of deposited PZT films is an addition superior property of the hydrothermal deposition method. And a large thickness of the hydrothe
Data Loading...
