Preparation and characterization of BaTiO 3 thin films on MgO-buffered Si(100) substrates by RF sputtering
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Preparation and characterization of BaTiO3 thin films on MgO-buffered Si(100) substrates by RF sputtering Sangsub Kima) Department of Materials Science and Metallurgical Engineering, Sunchon National University, 315 Maegok-dong, Sunchon 540-742, Korea
Shunichi Hishita National Institute for Research in Inorganic Materials, 1-1 Namiki, Tsukuba, Ibaraki 305, Japan (Received 12 February 1996; accepted 23 September 1996)
We report the results of a study on the deposition and characterization of partially oriented BaTiO3 thin films on MgO-buffered Si(100) by radio-frequency magnetron sputtering. The structural and morphological characteristics of the MgO buffer layer were investigated as a function of substrate temperature. The x-ray u-2u, f scans, and observation of surface morphology revealed that MgO grew with a tendency of (001) orientation. Partially (00l) or (h00) textured BaTiO3 thin films were obtained on Si(100) with the MgO buffer layer while randomly oriented BaTiO3 thin films with large-scale cracks on the surface were made without the MgO layer. PtyBaTiO3yPt multistructures were formed on Si(100), MgOySi(100), and MgO(100) single crystal substrates to conduct preliminary electrical measurements for metal-insulator-metal type capacitor. Comparison of the crystallographic orientation, morphology, and electrical properties between the BaTiO3 films on Si(100) with and without the MgO buffer layer supported the favorable role of the MgO layer as a buffer for the growth of BaTiO3 films on Si(100).
I. INTRODUCTION
Ferroelectric BaTiO3 thin films have received great interest in the applications of thin-film capacitors, nonvolatile memory devices, electro-optic devices, etc.1 Many attempts have been made to achieve oriented or epitaxial thin films of BaTiO3 since they appear to have superior physical properties compared to nonoriented polycrystalline ones. Recently, they have been realized on oxide single-crystal substrates such as MgO,2,3 SrTiO3 ,4 and LaAlO3 ,5 using various deposition techniques. For device applications it is promising to form BaTiO3 thin films on Si substrates because the oxide substrates are not only expensive but also incompatible with the current semiconductor technology. However, severe interdiffusion between the film and the substrate tends to inhibit the growth of oriented BaTiO3 thin films on bare Si substrates.6 In order to prevent the interdiffusion and to achieve high quality ferroelectric oxide films, suitable buffer layers seem to be required between the Si substrate and the film. A variety of oxide thin films such as MgO,7–15 yttria-stabilized zirconia (YSZ),16,17 MgAl2 O4 ,18 and CeO2 19 that can be used as buffer layers have been grown epitaxially on Si. Among them, thin films of MgO can be a good diffusion barrier and a suitable substrate for a)
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http://journals.cambridge.org
J. Mater. Res., Vol. 12, No. 4, Apr 1997
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the epitaxial growth of perovskite ferro
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