Deposition of Highly (100) Oriented PZT Film Using Lanthanum Nitrate/Nickel Acetate Buffer Layer
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Deposition of Highly (100) Oriented PZT Film Using Lanthanum Nitrate/Nickel Acetate Buffer Layer Jong-Jin Choi,1,2 Byung-Dong Hahn,1 Joo-Hee Jang,3 Woon-Ha Yoon,1 Dong-Soo Park,1 and Hyoun-Ee Kim2 1
Smart Ceramics Team, Department of Future Technology, Korea Institute of Machinery and Materials, 66 Sang-Nam-Dong, Chang-Won, Gyeong-Nam, 641-831, Korea 2
School of Materials Science and Engineering, Seoul National University, Seoul, 151-742, Korea
3
Division of Materials Science and Engineering, Pukyong National University, Busan, 608-739,
Korea ABSTRACT Highly (100) oriented Pb(Zr,Ti)O3 [PZT] films were fabricated using lanthanum nitrate/nickel acetate double layers as a buffer layer, regardless of the other deposition conditions, such as the pyrolysis temperature, pyrolysis time, annealing temperature, and heating rate. The buffer layer was also acted as a very effective barrier against Pb-Si interdiffusion, thus allowing for the direct deposition of PZT films on Si, SiO2/Si, and glass substrates. The strong orientation was attributed to the formation of a crystalline intermediate phase between the PZT and lanthanum nitrate during annealing. The lanthanum nitrate/nickel acetate double layers became a lanthanum nickel oxide (LaNiO3), which shows good electrical conductivity, after an annealing process at 650oC. The nature and the role of lanthanum nitrate buffer as a layer for the growth of highly (100) oriented PZT films have been studied. The dielectric, ferroelectric, piezoelectric and electrooptic properties of the highly (100) oriented PZT films with a lanthanum nitrate/nickel acetate buffer layer were measured and compared with the values measured from the (111) and (100) oriented PZT films deposited without buffer layer. INTRODUCTION Lead zirconate titanate [Pb(ZrxTi1-x)O3, PZT] films have great potential for use in microactuators, sensors and memory applications. The polarization switching and high capacitance of a thin film configuration are attractive for memory devices such as dynamic random access memory (DRAM) and nonvolatile ferroelectric random access memory (FeRAM). Furthermore, the large piezoelectric constants and high electromechanical coupling factors of a PZT film are favorable for acoustic applications [1]. Because the ferroelectric properties of the PZT films originate from their structural anisotropy, it is essential to prepare highly textured or
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epitaxial thin films, in order to take full advantage of these properties. The piezoelectric properties of PZT film are strongly dependent on its crystallographic orientation. Du et al. [2] calculated the dependence of the piezoelectric properties on the crystallographic direction phenomenologically for tetragonal and rhombohedral PZT in threedimensional space. They concluded that for rhombohedral PZT, the d33 value along the perovskite [100] is much larger than that along the spontaneous polarization direction [111]. Also, the calculated expectations were experimentally proved [3,4]. This suggests that PZT film hav
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