Electrical Properties of Low-Temperature Processed PZT Thin Films with Preferred Orientations
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Department of Materials Science and Technology, Shonan Institute of Technology, 1-1-25 Tsujido-Nishikaigan Fujisawa, Kanagawa 251, JAPAN
ABSTRACT Ferroelectric Pb(Zro. 53Ti0.47)O 3 (PZT) thin films with preferred orientations were successfully deposited on the Pt/Ti/SiO 2/Si wafer at low temperature of 525 'C by the chemical solution deposition from molecular-designed precusor solution with 20 mol % excess lead than a stoichiometric composition. The composition of the resultant PZT thin films showed slightly lead excess than a stoichiometric composition. In addition, orientation of the resultant PZT thin films could be controlled by changing the pre-annealing temperature or insertion of thin PbO layer, which affected the interfacial state between Pt electrode and PZT thin films. The electrical properties of the resultant PZT thin films were also affected by the orientation of the resultant films. As a result, orientation of the low-temperature processed PZT thin films had large effect on the electrical properties of the resultant films. INTRODUCTION Pb(Zr, Ti)0 3 thin films have been attracting wide interest due to their high potential for various applications such as in optical modulator, non-volatile semiconductor memories and in high-frequency surface acoustic wave (SAW) devices. [1-3] PZT thin films are deposited by several techniques such as chemical vapor deposition, sputtering and chemical solution deposition (CSD). Among them, an alkoxide process is one of the most promising techniques for processing high-performance thin films because it offers precise control of compositions on a molecular scale as well as a low processing temperature. In this paper, orientation of the ferroelectric PZT thin film deposited on a Pt/Ti/SiO 2/Si substrate was successfully controlled at low temperature though alkoxide route. Ferroelectric PZT has a perovskite structure and, therefore, PZT thin films with good ferroelectricity have a polarization axis, showing the different electrical properties depending on the crystal orientations of the resultant films. Consequently, orientation control is essential for the PZT films to apply various electronic devises. In some papers, preferred orientation and the orientation mechanism for the PZT thin films on Pt electrode were investigated. Brooks et al. explained film orientation with a view point of phase transition rate of pyrochlore phase into perovskite phase which occurred during pre-annealing stage. [4, 5] Chen et al. explained that film orientation was determined by the phases formed at the interface between film and substrate. [6] Namely, PZT showed (111)- and (100)- orientation if the Pt5. 7 Pb intermetallic compound and PbO were formed at the interface, respectively. Tani et al. also demonstrated that PLZT showed (111) orientation when the Pt 3Ti intermetallic compound exsisted on the substrate. [7] Liu et al. 241
Mat. Res. Soc. Symp. Proc. Vol. 596 © 2000 Materials Research Society
suggested that PZT thin film had (111) orientation if the film was grown epitaxially, where
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