Ferroelectric transition in an epitaxial barium titanate thin film: Raman spectroscopy and x-ray diffraction study

• Published in: Journal of applied physics 2003-09, Vol.94 (5), p.3307-3312
• Main Authors: El Marssi, M., Le Marrec, F., Lukyanchuk, I. A., Karkut, M. G.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1596720

We have performed x-ray diffraction and Raman spectroscopy measurements in the temperature range of 300–873 K on a single phase epitaxially oriented BaTiO3 thin film grown by pulsed laser deposition on a single crystal MgO substrate. The θ–2θ room temperature diffraction measurements and asymmetric rocking curves indicate that the film is very weakly tetragonal with the c-axis parallel to the plane of the film. X-ray diffraction measurements up to high temperature reveal only a change in slope in the perpendicular to the plane lattice parameter around 450 K (in bulk Tc=395 K) indicating that a diffuse-like of phase transition is taking place. Room temperature polarized Raman spectra show that the film is indeed tetragonal with C4v symmetry and with the a-axis perpendicular to the film plane. Monitoring of the overdamped soft mode and the 308 cm−1 mode confirms that the phase transition is taking place over a wide temperature range according to the x-ray results. The increase of the phase transition temperature is attributed to the stress effect induced by the substrate.