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The phase stability of ferroelectric, epitaxial, polydomain BaTiO 3 thin films was examined using temperature-dependent x-ray diffraction (XRD) and in-plane electronic polarization measurements. The epitaxial BaTiO 3 thin films were grown on MgO(100) substrates by a metal-organic chemical vapor deposition process. As-deposited and annealed BaTiO 3 thin films with different domain structures were examined. Temperature-dependent plane-normal XRD analysis reveals well-defined phase transitions at 140 and 169°C in the c-and a-oriented films, respectively. The measured Curie temperatures are consistent with those predicted by Landau-Ginsburg-Devonshire theory as applied to polydomain BaTiO 3 thin films. Temperature-dependent in-plane electronic polarization measurements confirm that the 140°C Curie temperature observed in the c-oriented film is a well-defined second-order paraelectric-ferroelectric transition.

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