In–Situ Transmission Electron Microscopy Crystallization Studies of Sol–Gel-Derived Barium Titanate Thin Films |
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Authors: | Maria C. Gust Neal D. Evans Leslie A. Momoda Martha L. Mecartney |
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Affiliation: | Department of Chemical and Biochemical Engineering, University of California, Irvine, California 92697–2575;Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831–0117;Hughes Research Laboratories, Malibu, California 90265 |
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Abstract: | Barium titanate (BaTiO3) thin films that were derived from methoxypropoxide precursors were deposited onto (100) Si, Pt/Ti/SiO2/(100) Si, and molecular-beam-epitaxy-grown (MBE-grown) (100) BaTiO3 on (100) Si substrates by spin coating. The crystallization behavior of the amorphous-gel films was characterized using in-situ transmission electron microscopy heating experiments, glancing-angle X-ray diffraction, and differential thermal analysis/thermogravimetric analysis. Amorphous-gel films crystallized at a temperature of ∼600°C to an intermediate nanoscale (5–10 nm) barium titanium carbonate phase, presumably BaTiO2CO3, that subsequently transformed to nanocrystalline (20–60 nm) BaTiO3. Random nucleation in the bulk of the gel film was observed on all substrates. In addition, oriented growth of BaTiO3 was concurrently observed on MBE-grown BaTiO3 on (100) Si. High-temperature decomposition of the intermediate carbonate phase contributed to nanometer-scale residual porosity in the films. High concentrations of water of hydrolysis inhibited the formation of the intermediate carbonate phase; however, these sols precipitated and were not suitable for spin coating. |
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