Epitaxial growth of sol-gel PLZT thin films
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Won Jong Lee Department of Electronic Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Kusong Dong 373-1, Yusung Gu, Taejon, Korea
Kwangsoo No Department of Ceramic Science and Engineering, Korea Advanced Institute of Science and Technology, Kusong Dong 373-1, Yusung Gu, Taejon, Korea (Received 17 May 1993; accepted 6 October 1993)
Epitaxial lead lanthanum zirconate titanate [PLZT(9/50/50)J thin films were fabricated on various single crystal substrates using the spin coating of metallo-organic solutions. The films were heat-treated at 700 °C for 1 h using the direct insertion method. The films were epitaxially grown with (100), (100), and (110) being parallel to the SrTiO3(100), the MgO(100), and the sapphire (0112) substrates, respectively. The epitaxy of the films was investigated using x-ray diffraction, pole figures, rocking curves, and scanning electron microscopy.
I. INTRODUCTION Much attention has been paid recently to lanthanummodified lead zirconate titanate (PLZT) solid solution systems which are well-known ferroelectric materials.1"13 Because PLZT is transparent in the visible and the near infrared region of the electromagnetic waves and has excellent dielectric and electro-optic properties, it is a candidate material for electronic and electro-optic applications. Recently, thin films of PLZT materials have attracted much interest for fabricating novel functional devices, such as thin film capacitors, ferroelectric random access memories (FRAM), optical waveguide modulators, display, and other electro-optic devices.6"9 Early work on the fabrication of PLZT thin films was mainly based on vacuum deposition techniques such as sputtering and evaporation. Ishida et al.10 succeeded in the epitaxial growth of PLZT thin films on SrTiO3, GaP, GaAs, and c-plane sapphire substrates using rf magnetron sputtering. Although vacuum deposition techniques are powerful methods for the epitaxial growth of the PLZT thin films, they have a serious problem which occurs due to the processing complexity of multicomponent systems. Recently, chemical sol-gel processing of the PLZT thin films has been reported.1'2'4'12'13 The sol-gel method is one of the most important techniques for fabricating ceramic thin films since it provides a high-purity, low temperature synthesis and, especially, a precise composition control. Baringay and Dey12 classified epitaxial films according to three types: (1) highly oriented polycrystalline films consisting of a complete z-axis orientation and a random orientation in the x-y plane, (2) crystalline films 420
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J. Mater. Res., Vol. 9, No. 2, Feb 1994
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with a single crystal-like texture consisting of a complete z-axis orientation and low angle grain boundaries in the x-y plane, or (3) truly single crystalline films. The oriented polycrystalline thin films may have both high and low angle grain boundaries. The single crystalline thin films have no grain boundaries except for other defects such as twins, s
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